Oxygen-modulated engineering of Cu^0–Cu^+ interfaces for CO_2-to-C_2H_4 photoreduction

Domain: physics
Published: 2025-12-26
Editorial outcome: major_revision

Abstract
CO -to-hydrocarbonfuelconversionviaartificialphotosynthesisislimitedby
catalystpoisoningunderhighO partialpressuresandsluggishC -product
2 2
formation.Herein,Ru Cu(Cu0–Cu1+)/CeO catalystswithadaptiveO toler-
0.6 1 2 2
ancearepreparedbyO -mediateddynamicinterfacialreconstruction.Single-
2
atomRudopingatCelatticesitescreatesatrigonalprismaticcoordination
configuration,enablingproton-coupledelectrontransferandaccelerating
H Odissociation.PhotothermaleffectpromotesO -drivenself-assemblyof
2 2
Cu0–Cu1+charge-gradientinterfaceswithinRu/Cualloyclusters,thereby
optimizingtheadsorptionbehaviorof*CHOCOintermediatesandrestruc-
turingtheC–Ccouplingpathway.Interfacialchargecascadetransferand
geometricsitesynergythermodynamicallyshifttheproductselectivityfrom
C toC ,asdeterminedbyoperandospectroscopyandelectronicstructure
1 2
analysis.Underconcentratedsolarirradiation,thecatalystproduces549±20
μmol·g−1C H with74.3%selectivityand0.5%solar-to-chemicalenergycon-
2 4
versionefficiency—25-foldhigherthanthatinnon-concentratedsystems.
Dynamicinterfacialregulationfacilitatesprecisecarbonchainsynthesisin
complexreactionnetworks.

Introduction
Acentralconstraintimpedingthepracticalimplementationofartificial catalytic activity through dual thermodynamic and kinetic inhibition:
photosynthesis is the efficient conversion of carbon sources under (1)Thermally,theoxygenreductionreaction(ORR)competeswiththe
oxygen-richenvironments—encounteredinindustrialfluegasorambi- targetCO reductionreaction(CORR)forelectrontransferpathways5;
2 2
entair1,2.Thisfundamentalchallengearisesfromcascadeattenuationin (2) Kinetically, persistent accumulation and monolayer coverage of
solar-to-chemicalenergyconversion.Prevailingstrategiesforimproving oxygen adsorption states on catalyst surfaces obstruct CO chemi-
2
energyefficiencyemployconcentratedlightsystemstogeneratetran- sorption and activation pathways. Ultimately, conversion efficiency
sient high-temperature microenvironments and elevated photon-flux decreasesby2–3ordersofmagnituderelativetoanaerobicsystems6.
densities on catalyst surfaces3,4. However, this approach accelerates Currentoxygen-tolerancestrategies(physicalisolation/surfacepassiva-
waterdissociation,triggeringexplosiveproliferationoftheO bypro- tion) have remained fundamentally limited by the oxygen-as-poison
2
duct(withmolaryieldsreaching3–5 timesthoseoftheprimaryCO paradigm and competitive adsorption framework7. These approaches
2
reduction products). Consequently, it induces an exponential rise in passivelysuppressORRbutfailtomitigatesystem-levelperturbations
systemoxygenpartialpressure,establishingaself-reinforcingnegative induced by drastic oxygen partial pressure fluctuations, creating
feedbackloopwhereintensifiedlightinput↔microenvironmentdete- inherentincompatibilitywithreal-worldoxidativeenvironments.Con-
rioration mutually amplifies. This loop comprehensively suppresses sequently, designing intrinsically oxygen-tolerant gas-solid catalytic
interfacesisimperative.SuchsystemsmustefficientlymitigateO poi-
2
soningwhileproductivelyleveragingoxygenmoleculesastriggersto
inducesteady-stateself-assemblyofactivesites.Thiswouldenablethe
directional construction of catalytic microenvironments adaptive to
high-oxygen conditions, thereby decoupling efficient C=O bond acti-
vationfromcompetitiveCO/O adsorptionkinetics—aprerequisitefor
2 2
practicaldeployment.

During hydrogenation-driven carbon-chain growth, single-atom
catalysts(SACs)leveragetheiruniquelocalizedelectronicstructures
andcoordinativeunsaturatedtoefficientlydissociatewatermolecules,
continuouslysupplyingactivehydrogenspecies(*H)whileoptimizing
proton-coupled electron transfer (PCET) kinetics8. Ru single atoms
stabilizedinthe0<δ+<4oxidationstate(Ruδ+)preciselymodulatethe
d-bandcenterviatheirt orbitalconfiguration.Synergisticinteraction
2g
with the support’s strong electron effects establishes an electron-
deficient microenvironment9, enhancing OER efficiency via three
mechanisms:(1)StrengtheningchemicaladsorptionofH Oatactive
2
sites and lowering the O–H bond dissociation energy barrier;
(2)Optimizingadsorptionstrengthofkeyoxygenintermediates(*OH,
*O,and*OOH),circumventingconventionalSabatierprincipallimita-
tions; (3) Significantlyreducing kinetic overpotential inPCET steps.
However,spatialconfinementatsingleatomicsitesinducescompeti-
tiveadsorption,thermodynamicallystabilizingthelinearadsorption
configurationof*COintermediatesduringCO activation.Thisresults
2
insymmetrymismatchbetweentheCatom’sp orbitalandthemetal
x
atom’sdz²orbital,severelyinhibitingthesp3hybridizationtransition
requiredforC–Ccoupling.Toovercomethislimitation,amulti-active-
sitesystemintegratingsingleatomswithalloyclustersisessential.The
corestrategyinvolvesconcertedmodulationofdiscreted-bandorbi-
talsandinterfacialchargedistributiontodrivethedynamictransition
of*COfromlineartobridgingadsorption,therebyfacilitatingcarbon
chain growth10. Under aerobic conditions, Cu-based polymetallic
interfaces exhibit dual advantages in terms of O activation and
2
directional carbon chain construction. The Cu sites dynamically
coordinatetoforM–O–Cuantioxidationnetworks,whichselectively
destruct reactive oxygen species and enable the catalytic micro-
environment to self-repair, thereby avoiding catalyst deactivation
under oxidative conditions11. Simultaneously, Cu0–Cu1+ charge-
gradient interfaces are generated in situ, which induce the recon-
structionof*CHOCOadsorptionsitesthroughelectronredistribution
andbreakthespatialsymmetryoflinearadsorption configurations.
This balances the coverage of intermediates with their reaction
kinetics, resulting in a significant enhancement in selectivity for
hydrocarbonproducts12.

ToaddressthedualchallengesofkinetichysteresisinC–Ccou-
plingandtheoxidativedeactivationofmetalactivesitesinoxygen-rich
systems,weproposeanO -mediateddynamicinterfacialreconstruc-
2
tion strategy and successfully construct a Ru Cu(Cu0–Cu1+)/CeO
0.6 1 2
catalyticsystemwithself-adaptiveO tolerance.Unlikeconventional
2
single-sitedesigns,whichexhibitinherentlimitationsowingtotheir
staticelectronicconfigurations,thisdesigndynamicallyself-optimizes
the active microdomains during catalytic processes through cross-
scalefunctionaldecouplingbetweentheRusingleatomsandRu/Cu
sub-nanoscale alloy clusters. Theoretical calculations and in situ
characterizations confirmed that the Ru single atoms substitute Ce
latticesitestoformatrigonalprismaticcoordinationconfiguration,
whichinducesproton-coupledelectrontransfertomaintainefficient
hydrogen spillover. Meanwhile, the photothermal effectinduced O
2
accumulation triggers dynamic self-assembly of Cu0–Cu1+ hetero-
interfaces. These charge-gradient interfaces reduce the formation
energyofthecriticalintermediate*CHOCO.Thetransitionfromstatic
sitestodynamicinterfacesimprovestheC H selectivityfrom0%to
2 4
74.3%underhighO partialpressures.Thisstudyprovidesnewper-
2
spectives on dynamic interface regulation for precise carbon chain
constructionincomplexreactionenvironments.

Results
CatalystdesignforCO photoconversion
2
In heterogeneous catalysis, in situ modulation of the electronic
structure and coordination environment of metal active sites is
essentialforimprovingthecatalyticperformance13.Single-atommetal
species(denotedasM)havewell-definedactivesites;however,owing
1
to their isolated active centers, they exhibit inherent limitations in
complex redox reactions that require molecular co-adsorption
(Fig.1a).Incontrast,metalclusters(denotedasM )possessmultiple
n
active centers that enable small-molecule activation; however, their
performanceisconstrainedbytheirstructuralinstabilityandexcessive
chemicaladsorption(Fig.1b).Theselimitationscanbeovercomeby
strategically positioning M sites adjacent to M active centers to
n 1
produce dual-active-site M +M systems. The synergistic catalytic
n 1
effectsoftheM andM sitesenhancethereactionkineticsandsig-
n 1
nificantlyimprovetheoverallcatalystperformance(Fig.1c).

Despitenotableprogressinthecatalyticstudiesofmetallicspe-
cies, critical challenges persist (Fig. 1d). First, constructing catalytic
sites with spatial/energy multiscale regulation capabilities presents
higher-dimensional design challenges compared to traditional M
1
systems.AccordingtotheSabatiervolcanocurvetheory,idealcata-
lysts must precisely modulate the adsorption free energy (ΔG*) of
reactionintermediatestoovercometheconstraintsimposedbylinear
scaling relationships on the catalytic activity maxima14. Second,
althoughM +M synergisticactivesitescanintegratemultiplereac-
n 1
tionpathways,theM sitesareoftenpronetoexcessivechemisorption
n
andexhibitalimitedabilitytoeffectivelystabilizekeyintermediates15.
Consequently, the design of metallic species near single-atom
sitesthatexhibithighintrinsicactivity,selectivity,andstabilityiscri-
tical for enhancing the efficiency of complex catalytic reactions
(Fig.1e(i)).Underhighphoton-fluxdensityandthermalflowcoupled
conditions,itmaybepossibletoutilizeO asamediatortoinduce
2
dynamicvalencestateevolutionofthemetalspeciesoncatalystsur-
faces,ultimatelyenablingtheinsitutopologicalrestructuringofhet-
erogeneous interfaces (e.g., Cu0–Cuδ+). By regulating the oxidation
statesofthemetalsites,theycanmorereadilyadsorbintermediates
and catalyzeC–Ccoupling(Fig.1e(ii)).Consequently,thisapproach
effectivelyemploysbyproductO whilealsoenhancingtheC selec-
2 2
tivityandactivity(Fig.1e(iii)).

Herein,wefabricatedaRu/CucompositesystemonaCeO sup-
2
port via wet chemical reduction. Coexisting single atoms and sub-
nanoscale alloy clusters were successfully constructed during this
dynamicreduction process(SupplementaryFig. 1).Owing to differ-
ences in their reduction kinetics, Ru3+ and Cu2+ undergo stepwise
reduction to produce metallic atoms, which gradually aggregate
throughthermodynamicallydrivendiffusionandcollision16.Thelat-
tice mismatch between Ru and Cu phases, combined with surface
energy differences, induces atomic segregation during alloy forma-
tion.Duringthegrowthofcrystalnuclei,migrationhysteresisarises
due to Ostwald ripening and the higher energy barrier for Ru
diffusion17.SomeRuatomsoccupytheCulatticesitesviasubstitution,
whereasothersarepreventedfromenteringtheCulatticeowingto
localized concentration fluctuations and abrupt Gibbs free energy
changes. These atoms, therefore, stabilize in monoatomic states
throughsurfacecoordinationrestructuring.Notably,thisresultsina
distinctstructureinwhichisolatedRuatomscoexistwithRu/Cualloy
clusters. We employed density functional theory (DFT) to system-
aticallyinvestigatetheformationenergiesandthermodynamicstabi-
lities of Ru/Cu alloy clusters. A total of 34 supercell models with
distinctstoichiometricratioswereconstructed(Fig.1f).Amongthese,
the Ru Cu configuration exhibited the lowest formation energy
3 5
(0.76eV).Theformationenergiesofalloyclusterswithotheratomic
proportions graduallyincreased as the Ru or Cu content increased,
confirming the intrinsic stability of RuCu as a thermodynamic
3 5
ground-statestructure.

Materialcharacterization
Transmissionelectronmicroscopy(TEM)revealedthattheCeO sup-
2
porthadahighlyoriented,regularoctahedralmorphology,withparticle
sizesrangingfrom20to50nm(SupplementaryFigs.2and3).High-
angle annular dark-field scanning transmission electron microscopy
(HAADF-STEM)revealedlatticeparameterscorrespondingtothechar-
acteristic(111)planeofCeO (interplanarspacingof0.31nm),confirm-
2
ingitssingle-crystalnature(Fig.2a).Toanalyzethedistributionpatterns
of metallic Ru and Cu on the CeO support, three-dimensional con-
2
formationalcharacterizationofRu Cu/CeO (Co-existenceofmona-
0.6 1 2
tomic Ru and Ru/Cu alloy) was conducted using atomic-resolution
HAADF-STEM.TheresultsrevealedthatRuatomswerestablyanchored
ontheCeO supportinamonoatomicdispersionwithnodetectable
2
agglomeration (Fig. 2b). Direct imaging further visualized Ru atoms
occupying Ce lattice sites along the [111] zone axis (Supplementary
Fig.4),withline-scanprofilesconfirminglocalizedlatticecontraction.
Additionally, XRD patterns indicated that Ru doping induced a sys-
tematic high-angle shift of ~0.15° in the main diffraction peaks (Sup-
plementaryFig.5).Thislatticecontractionresultedfromsubstitutionof
smallerRu3+ionsforCe4+ions,causinganisotropiccompressionofthe
fluorite unit cell. Sub-nanoscale alloy clusters (1–3nm) were also
observed on the support surface (Fig. 2c and Supplementary Fig. 6).
Theirlatticeparameterscorrespondtothe(111)planeofRuCu(inter-
planarspacingof0.22nm),whichisslightlyexpandedcomparedwith
thatofpureCu(0.21nm)18.ThisobservationalignswithVegard’slaw
andvalidatestheproposedalloyingmechanism19,wherebyRuatomsare
incorporatedintotheCulatticeviaatomicsubstitution.STEM-energy
dispersive X-ray spectroscopy (EDX) elemental mapping revealed the
spatial co-localization of Ru and Cu within the sub-nanoclusters
(Fig.2d).EDSlinescansacrossrepresentativealloyclusters(Profiles1
and2,Fig.2e)wereusedtogeneratesuperimposedintensityprofilesof
Ru Lα and Cu Kα signals (Supplementary Fig. 7), confirming atomic-
scaleelectroncloudoverlapbetweenthetwometallicelements.Thisisa
characteristicfeatureofintermetalliccompounds.

SynchrotronradiationX-rayabsorptionspectroscopy(XAS)was
employed to further elucidate the structural characteristics of the
metallicactivecenters.RuK-edgeX-rayabsorptionnearedgestruc-
ture (XANES) analysis demonstrated that the absorption edge at
~22,116eVwaspositionedbetweenthatofmetallicRufoil(~22,113eV)
and an RuO reference material (~22,120eV), confirming that the
2
averageoxidationstateoftheRuspeciesliesbetweenthemetallic(0)
and+4valencestates(Fig.2f).Usingthelinearcorrelationbetween
K-edgeshiftandoxidationstatefortransitionmetals,wedetermined
anaverageRuoxidationstateof+1.96(SupplementaryFig.8).TheRu
K-edge Fourier-transform extended X-ray absorption fine structure
(FT-EXAFS)spectrumofRu Cu/CeO exhibitedthreecoordination
0.6 1 2
peaks atbond distances (R) of 1.6–2.3Å (Fig. 2g). Multi-shell fitting
analysis was used to quantitatively resolve the coordination paths
(SupplementaryFig.9).Threecoordinationstructureswereidentified:
short-range Ru–Cu metallic bonding (coordination number [CN] =
0.6±0.2atR=2.53Å),second-nearest-neighborRu–Rucoordination
(CN=1.6±0.1atR=2.68Å),andlong-rangeRu–Ointeractions(CN=
5.9±0.2atR=2.01Å)(SupplementaryTable1).TheRu–Ocoordina-
tionnumberandbondlengthprovidedstrongevidencethataportion
ofRuspeciesexistedasatomicallydispersedsingleatoms.ThisCN
valuecloselymatchedthetheoreticalcoordinationnumber(~6)forRu
in octahedral sites within the fluorite structure of CeO . Combined
2
withthe observedRu–Obond distance,these resultsdemonstrated
thatasignificantpopulationofRuatomsoccupiedCeO latticesites,
2
forming stable, high-coordination bonds with oxygen atoms and
thereby anchoring as single-atom species (Ru–O–Ce). This high-
coordination environment was distinct from surface-adsorbed oxy-
gen species, which typically exhibited lower coordination numbers
(CN<2). This discovery of a multiscale coordination architecture
revealsthatRuatomsprimarilyexistasisolatedsingleatomsinthe
Ru Cu/CeO catalyst,withothersformingsub-nanoclusterswithCu.
0.6 1 2
IntheXANESspectra,theCuK-edgeabsorptionenergy(Fig.2h)
closelyalignedwiththatofmetallicCufoil(8,979eV),confirmingthat
Cu predominantlyremainsinthemetallicstate.Furthermore,EXAFS
analysis revealed that the coordination characteristics diverge from
those of conventional metallic lattices (Fig. 2i). Compared with
metallic Cu with an ideal face-centered cubic structure (theoretical
CN=12atR=2.54Å)20,thesampleexhibitsasharpreductioninCu–Cu
coordination number (CN=1.5±0.1). A Cu–Ru metallic bonding
structurewasalsoobserved(CN=1.5±0.3atR=2.63Å).Theseultra-
lowcoordinationnumbers(CN<3)exceedthesize-effectlimitations
typically observed in monometallic Cu nanoparticles, thereby con-
firmingtheformationofsub-nanoclusters.TheweakCu–Ocoordina-
tion (CN=1.1±0.1 atR=1.88Å), with bond lengths characteristic of
oxygenspeciesadsorbedonmetallicCusurfaces(1.85–1.90Å),indi-
catesthepresenceofweakinteractionsatthesupportinterfacerather
thanoxidizedcrystallinephases(SupplementaryTable2andSupple-
mentaryFig.10).

Based on joint time-frequency domain analysis of the wavelet
transformsatthebimetallicK-edges,wefurtherprovidedadefinitive
criterionforidentifyingRu–Cumetallicbonds.TheRuK-edgewavelet
transformexhibitedahigh-intensitysignalatcoordinate(R,k)=(2.3Å,
9.3Å−1) (Fig. 2j). Here, the strong high-k response (>9Å−1) directly
correlates with quantum interference effects in Ru–Cu scattering
pathways. Synchronous Cu K-edge wavelet transform analysis
captured corresponding Cu–Ru scattering signals at (R, k) = (2.2Å,
8.0Å−1). This corroboration of the multiscale structural parameters
directlyevidencesthecoexistenceofRusingleatomsandRuCusub-
nanoscaleclustersintheRu Cu/CeO catalyst.
0.6 1 2
Consideringtheselectivesingle-atomdispersionobservedduring
catalystsynthesis,wesystematicallyinvestigatedthedopingbehavior
andstabilityofRuandCusingleatomsonCeO (111)surfacesusing
2
DFTcalculations21.Intheoptimizedstructure,RuatomsoccupyingCe
sites via latticesubstitution adopta trigonal prismaticcoordination
withsixneighboringOatoms,exhibitingaformationenergy(E )of
form
−7.02eV(Fig.2k).Incontrast,Cuatomsatthesamesubstitutionsite
adoptasquareplanarcoordinationconfiguration,withasignificantly
higher E of −4.12eV (Fig. 2l). These results confirm that the Ru
form
single-atom/CeO systemhassuperiorthermodynamicstability.
2
Projected density of states (PDOS) analysis revealed distinct
electroniccouplingbehaviorsofthedopedRuandCuwiththeirseven
neighboringOatomsontheCeO (111)surface.Thebandcenterdif-
2
ferencebetween the O2pand Ru 4dorbitals (Δ=|ε −ε |) is
2p(O) 4d(Ru)
0.21eVforspinupanddownorbitsmallerthanthatbetweentheO2p
andCu3dorbitals(Δ=|ε −ε |,about0.37eV),indicatingthe
2p(O) 3d(Cu)
relativelymoresubstantialrehybridizationbetweentheRu4dandO2p
orbitals(Fig.2m–n).CrystalorbitalHamiltonpopulation(COHP)ana-
lysisfurtherrevealedthenatureoftheRu–OandCu–Obonds22.Itwas
found that electrons primarily occupy the bonding states of Ru–O
bonds, while the antibonding state was rarely occupied. For Cu–O
bonds, however, electrons occupied both bonding and antibonding
states(Fig.2o–p).Themuchmorenegativevaluesoftheintegrated
COHP (ICOHP) for Ru–O bonds (−0.63) than that for Cu–O bonds
(−0.13)indicatedtherelativelystrongerbondingbetweenRuandthe
coordinatedOatoms.Overall,integratedDFTmodelingandelectronic
structureanalysisconsistentlydemonstratethatdopedRusingleatom
is a thermodynamically more favorable and stable dopant than Cu
atomintheCeO (111)surfaces.
2

PhotothermalCO reduction
2
Employing a research strategy that integrates theoretically guided
design of catalysts with multiscale experiments, we elucidated the
effectsofthesingle-atom/sub-nanoscalealloyclustersystemsonthe
photothermalCO reductionperformance.First,thecatalyticactivity
2
ofbareCeO andsingle-atomcatalysts(Ru /CeO andCu/CeO )was
2 0.6 2 1 2
evaluated for the co-reduction of CO and H O under non-
2 2
concentrated solar irradiation (Fig. 3a). The spectral characteristics
ofthelightsourceandcatalystsurfacetemperatureareillustratedin
SupplementaryFigs.11and12.TheRu /CeO catalystachievedCH
0.6 2 4
andCOproductionratesof4.7and7.7μmol·g−1·h−1,respectively.This
contrastssharplywiththeperformanceofthebareCeO andCu/CeO
2 1 2
catalyst,whichbothexhibited100%COselectivity(productionratesof
5.2and13.6μmol·g−1·h−1,respectively).Thisdistinctbehaviorhighlights
howRusingle-atomsitesenhancetheH Odissociationkinetics;single-
2
atom sites facilitate proton-coupled electron transfer, which con-
tinuously supplies *H species to the reaction environment, thereby
drivingthedeephydrogenationofCO toCH .TheGibbsfreeenergy
2 4
fortheO evolutionreactionisillustratedinSupplementaryFig.13.
2
TheRu /CeO catalysthadalowenergybarrier(1.83eV)fortherate-
0.6 2
determining*O→*OOHstep,therebysignificantlyenhancingtheO
2
evolutionkinetics.Incontrast,forCu/CeO ,thereactionterminatedat
1 2
theCOdesorptionstageowingtokineticlimitationsin*Hsupply.This
corroboratestheroleofsingle-atomRuinoptimizingtheadsorption
configuration of oxygen-containing intermediates. Theoretical
screening (Fig. 1f) identifies the RuCu cluster as the thermo-
3 5
dynamically most stable and kinetically most accessible structure
withintheRu Cu/CeO system,providingafoundationalframework
x y 2
forpotentialactivesiteconfigurationsinpracticalcatalysts.Guidedby
thisprediction,bimetallic(Ru Cu/CeO ;x=0.2–1,y=1–0.2)catalysts
x y 2
withbothRusingle-atomsitesandsub-nanoscalealloyclusterswere
prepared (Supplementary Table 3). The Ru Cu/CeO catalyst,
0.6 1 2
developedthroughprecisecompositioncontrol,demonstrated
exceptionalcatalyticperformance,withCO,CH ,andO production
4 2
rates of 40.5, 7.8, and 50.8 μmol·g−1·h−1, respectively (Fig. 3a). This
significantlyoutperformedcatalystswithotherRu/Curatios.Theclose
stoichiometric match (Ru:Cu ≈ 3:5) to the theoretically predicted
optimal Ru Cu structure validates the computational guidance for
3 5
synthesizingmaterialswithhigh-activityarchitectures.

Toenhancethedirectsolar-to-chemicalenergyconversioneffi-
ciency,weperformedexperimentsunderconcentratedsolarirradia-
tion(5000mW·cm−2)withtheaimofincreasinghigh-energyelectron
transfers and localized thermal effects by harnessing solar-induced
photon–phononcoupling(SupplementaryFig.14).Wesystematically
optimized H O concentration to maximize performance (Supple-
2 2
mentaryFig.15).ThecriticaldesignparametersoftheCeO -basedand
2
single-metalcatalystswereoptimized(SupplementaryFigs.16and17).
Additionally, the catalyst surface temperatures and UV-Vis diffuse
reflectance spectra were obtained (Supplementary Figs. 18 and 19).
Electronicbandstructureanalysesdemonstratedthatallcatalystscan
matchthethermodynamicpotentialsforCO reductionandH Ooxi-
2 2
dationreactions(SupplementaryFigs.20and21).TheRu Cu/CeO
0.6 1 2
catalyst exhibited distinct product selectivity owing to this energy-
fieldcoupling,withaC H productionrateof274.5μmol·g−1·h−1and
2 4
concurrent O evolution rate of 910.5 μmol·g−1·h−1 (Fig. 3b, Supple-
2
mentary Fig. 22 and Supplementary Table 4). This sacrificial agent
systemdidnotsignificantlyenhancecatalyticperformance(Supple-
mentary Fig. 23). The fundamental limitation stems from inherent
differencesbetweengas–solidsystemsandconventionalliquid–phase
reactions.Incontrast,adualsingle-atomcatalyst(RuSAs+CuSAs/
CeO ) and a catalyst with coexisting Ru single atoms and Cu sub-
2
nanoclusters(RuSAs+Cusub-nanocluster/CeO )yieldedonlyCOand
2
CH during photothermal CO reduction (Supplementary
4 2
Figs.24and25).Notably,thiscorrespondstoasignificantenhance-
mentinC H selectivityfrom0%to74.3%comparedwiththatunder
2 4
non-concentrated solar irradiation, with electron selectivity reach-
ing91.4%.

Time-resolved kinetic analysis revealed the temporal trend of
product evolution (Fig. 3c). During the initial reaction phase
(0–30min),COaccumulatedrapidly,reachingapeakconcentrationof
794±45μmol·g−1at30min.SomeC H evolution(62.6±8μmol·g−1)and
2 4
substantialO generation(640±25μmol·g−1)werealsoobserved;
2
therefore,wehypothesizedthatO ,whichisproducedasabyproduct
2
oftheCO reductionreaction,inducesselectivesurfacereconstruc-
2
tionoftheRu/Cualloyclustersthroughoxidativeetching.Thisprocess
partially converts the Cu0 sites into Cu1+ species, forming dynamic
Cu0–Cu1+ charge-gradient interfaces (catalyst designation:
Ru Cu(Cu0–Cu1+)/CeO ).ThesegradientinterfacesenhancetheC–C
0.6 1 2
couplingcapability.Insubsequentreactionstages(30–120min),C H
2 4
productionexhibitedquasi-linearkineticbehavior,withitsyieldpro-
gressivelyincreasingto549±20 μmol·g−1. Meanwhile, the CO con-
centration decayed following quasi-first-order kinetics. This C →C
1 2
transition aligns with the Langmuir–Hinshelwood surface reaction,
indicatingthatthere isdynamiccompetitionbetween the C H for-
2 4
mationpathwaysandconsumptionofCOintermediates.Torigorously
verify if oxygen is further reduced during CO reduction, we per-
2
formed catalytic experiments under concentrated solar irradiation.
Post-extraction analysis detected no quantifiable H O (Supplemen-
2 2
taryFig.26).Massspectrometry-calibratedandbaseline-correctedgas
chromatographydatavalidatedtheconcurrentenhancementofC H
2 4
selectivitywithCOconversion(SupplementaryFigs.27and28).

Toestablishtheimportanceofphotothermalcouplingeffectsin
C H generation, we excluded contributions from single-energy
2 4
modalities (pure photon excitation or thermal activation alone)
through multidimensional control experiments (Fig. 3d): (1) Under
concentratedUVirradiationorpurethermalactivation(462°C)alone,
noC H production was detected,even when theO concentration
2 4 2
was maintained at 640±25 μmol·g−1 (equivalent to the measured
concentrationunderphotothermalconditions);(2)Maintainingtem-
perature at 462°C while irradiating with lower-intensity UV light
(50–250mW·cm−2) also yielded no C H (Supplementary Fig. 29).
2 4
Controlexperiments—includingsystemswithoutH O,CO ,orcatalytic
2 2
components—similarly demonstrated no C H signals. Furthermore,
2 4
the catalytic system can be defined as a thermally assisted photo-
catalyticsystem(SupplementaryFigs.30and31).Thehighphoton-flux
density demonstrated a significant negative correlation with the
apparentactivationenergy(SupplementaryFigs.32and33).Toelu-
cidatethemechanismsbywhichO dynamicallyregulatestheC–C
2
couplingprocess,weconductedconcentration-gradientexperiments
coupledwithinsitusurfaceanalysis.TheO concentration-response
2
functionalrelationship(R2=0.99)demonstrateshighgoodness-of-fit
of the standard curve (Supplementary Fig. 34). The experimental
resultsrevealedthat,astheinitialO concentrationincreasedfrom0
2
to429μmol·g−1,theC–Ccouplingreactiontimereducedfrom120to
97min(Fig.3e).

ThevalencestateoftheCuactivesiteswasmonitoredusingquasi
in situ X-ray photoelectron spectroscopy (XPS). During the initial
reactionphaseunderconcentratedsolarirradiation(0–15min),theCu
LMMAugerspectraexhibitedonlythecharacteristicpeaksofmetallic
Cu (Cu0; 918.6–919.4eV). At 30min, Cu1+ species emerged
(913.4–913.9eV),andtheirrelativeabundanceprogressivelyincreased
to58%asthereactionproceededfurther(Fig.3f)23.NoCu2+species
were detected in the higher binding energy range during the quasi
insituXPSanalysis(SupplementaryFig.35).QuasiinsituXANESana-
lysisrevealedthattheCuK-edgespectrummatchedthatoftheCufoil
referenceat0min.Theedgeshiftedtohigherenergiesafter30minof
exposure,indicatingoxidationtoCuδ+.Thisshiftintensifiedby60min
and stabilized at a position intermediate between the Cu0 and Cu1+
reference spectra by 120min (Supplementary Fig. 36), indicating a
mixedCu0/Cu1+oxidationstate.Thisvalenceevolutioncorrelateswell
withtheresultsoftheO concentrationgradientexperiments;O acts
2 2
asanoxidant,mediatingtheinsituformationofdynamicCu0–Cu1+
interfaces, thereby optimizing the adsorption of C–C coupling
intermediates.

In concentrated solar irradiation regulation experiments
(10–60suns,1sun(100mW·cm−2)),theO generationratewasposi-
2
tivelycorrelatedwiththeirradiationintensity(Fig.3g).However,C H
2 4
production exhibited light-intensity-dependent nonlinear behavior
with a distinct threshold. C H formation commenced at 30 suns
2 4
(298.6°C), achieving 7.3% selectivity and O yield of 550 μmol·g−1.
2
Under identical thermal conditions with auxiliary illumination
(50–300mW·cm−2),noC H formationwasobserved(Supplementary
2 4
Fig.37).ThisconfirmsthatO concentrationistheprimarylimiting
2
factor.At50suns,theC H selectivityhadincreased10-foldto74.3%.
2 4
This nonlinearamplification effectcauses a 25-fold enhancementin
thesolar-to-chemicalenergyconversionefficiency(0.5%vs.0.02%for
that under non-concentrated solar irradiation, Supplementary
Table 5). The Ru Cu(Cu0–Cu1+)/CeO catalyst maintains excellent
0.6 1 2
catalytic activity through seven consecutive cycling tests (Fig. 3h).
Furthermore,thermogravimetricanalysisrevealedthatminimalmass
loss(3.402%)occurredat500°C,whichwasattributedtothedeso-
rptionofphysicallyadsorbedH O;nobulkstructuraldecomposition
2
occurred (Supplementary Fig. 38). Differential scanning calorimetry
analysis showed no discernible endothermic or exothermic peaks
above300°C(SupplementaryFig.39),indicatingtheabsenceofsig-
nificantphasetransitions,decomposition,orotherthermallyinduced
structuralchanges.Scanningelectronmicroscopyconfirmedthatthe
catalystmorphologywaspreservedaftercycling,indicatingthatthe
lattice is structurally stable under high-temperature reaction condi-
tions(SupplementaryFig.40).InsituXPSanalysisrevealedthatsur-
face Cu species maintain a stable Cu0–Cu1+ configuration upon
illuminationcessationwithoutrevertingtotheirpre-irradiationstate
(Supplementary Fig. 41). Critically, this O induced reconstruction
2
persists post-irradiation, distinguishing it from transient photo-
generatedmetastablestatesandreversiblethermodynamicequilibria.
The persistent structural memory—formed non-equilibrium but
retained at equilibrium—establishes the Cu0–Cu1+ interface as an
intrinsicallystableactivecomponent.Theinterfacialchargedynamics
of the Ru Cu(Cu0–Cu1+)/CeO catalyst were elucidated in Supple-
0.6 1 2
mentaryFig.42.

Insitucharacterization
Product selectivity critically relies on the dynamic adsorption and
directionalactivationofreactants.DFTcalculationsrevealedreactant
adsorptiondynamicsonthreestructuralmotifs:theCeO substrate,
2
isolatedRusingle-atomsites,andRuCualloyclusters(Supplementary
Figs.43and44).RuCualloyclustersexhibitedoptimalCO adsorption
2
energy(−0.12eV),significantlyhigherthanvaluesforCeO (−0.06eV)
2
or Ru single-atom sites (−0.08eV). Incontrast, H O adsorption was
2
strongest on Ru single atoms (−1.01eV), exceeding adsorption on
CeO (−0.38eV)orRuCuclusters(−0.50eV),confirmingsite-specific
2
affinity for polar molecules. Notably, RuCu clusters showed the
strongest O adsorption energy (−2.70eV), approximately 1.50eV
2
more negative than those for CeO (−1.13eV) and Ru single atoms
2
(−1.81eV), demonstrating superior oxygen activation capacity. Col-
lectively,theseresultsestablishRuCuclustersassynergisticCO /O
2 2
activationcenters.

CO temperature-programmeddesorption(TPD)providedanin-
2
depthanalysisoftheadsorptionbehaviorofCO (Fig.4a).TheCu/
2
CeO catalyst exhibited a high-intensity desorption peak at 450°C,
2
demonstratingthattheCusiteshaveastrongCO adsorptioncapacity.
2
Thedesorptionpeakshiftedto250°CforRu /CeO ,indicatingthat
0.6 2
the Ru sites exhibit weak CO adsorption activity. The
2
Ru Cu(Cu0–Cu1+)/CeO catalyst had a significantly stronger deso-
0.6 1 2
rptionpeakat515°C,whichcorrespondstotheformationofmono-
dentatecarbonatespecies(m-CO 2−)24.DuringH O-TPD(Fig.4b),the
3 2
Cu/CeO catalystdisplayedonlyahigh-intensitydesorptionpeakat
2
416°C, corresponding to the associative dehydration of hydroxyl
speciesunderstrongmetal–supportinteractions25.Thus,theCusites
play a limited role in H O dissociation. In contrast, the Ru /CeO
2 0.6 2
catalyst exhibited a characteristic H O-dissociation-induced deso-
2
rption peak at 250–350°C. This phenomenon is attributed to Ru-
mediated H O dissociation on coordinatively unsaturated sites,
2
effectively releasing *H26. Notably, the Ru Cu/CeO and
0.6 1 2
Ru Cu(Cu0–Cu1+)/CeO catalysts also demonstrated distinct deso-
0.6 1 2
rptionpeaksat328and340°C,respectively,whicharecloselyasso-
ciatedwiththeH OdissociationactivityofRusingle-atomsites.O -
2 2
TPD revealed the dynamic oxidation behavior of the Ru/Cu alloy
clusters(Fig.4c).Ahigh-temperaturedesorptionpeakwasobservedat
294°C for the Cu/CeO catalyst, which reflects the intrinsic self-
1 2
oxidationcharacteristicsofCu0 speciesfromCu0 toCu1+,drivenby
strongchemisorption.Incontrast,forthebareCeO andsingle-metal
2
Ru /CeO catalysts, a desorption peak emerged at a significantly
0.6 2
lowertemperatureof130°C(ΔT=−164°Cvs.thatofCu/CeO ),which
1 2
correspondstothedesorptionbehaviorofweaklyphysisorbedO 27.
2
Thus, the Ru sites had limited O activation capability. Notably,
2
Ru Cu/CeO exhibitedasignificantlyenhanceddesorptionsignalat
0.6 1 2
368°C, suggesting that the bimetallic structure strengthens the
adsorptionstabilityofO onRu/Cualloy,therebypromotingthefor-
2
mationofdynamicCu0–Cu1+redoxinterfaces.Furtheranalysisofthe
Ru Cu(Cu0–Cu1+)/CeO system revealed a reduced desorption
0.6 1 2
intensityat377°C,directlycorroboratingthenotionthattheCu0–Cu1+
heterointerface suppresses excessive O adsorption via steric hin-
2
drance, thereby maintaining the metastable equilibrium of the Cu
species.CO-TPDwasperformedtoelucidatetheadsorptionbehavior
ofthekeyreactionintermediateCO(Fig.4d).TheRu /CeO catalyst
0.6 2
exhibited a characteristic desorption peak at 278°C, which corre-
spondstomoderate-strengthCOadsorption.Notably,thistempera-
tureisnearthecatalyticreactiontemperature(292.3°C),enablingCO
to participate stably insequential hydrogenation to formCH . Cu/
4 1
CeO exhibited a high-temperature desorption peak at 412°C, indi-
2
cating significantly stronger CO adsorption. However, this tempera-
turefarexceedsthepracticalreactionconditions(362.5°C),leadingto
asharpdeclineinCOcoverageduringthereactionandpreventingits
deep conversion. Importantly, the Ru Cu/CeO catalyst demon-
0.6 1 2
stratedanewdesorptionsignalat437°C.Thesubstantialincreasein
desorptiontemperature(ΔT=159°Cvs.thatofRu /CeO )confirms
0.6 2
thatRu/CualloyclusterssynergisticallyenhancetheCOsurfacecov-
erage, creating the necessary conditions for C–C coupling. Further-
more, the Ru Cu(Cu0–Cu1+)/CeO system exhibited a high-
0.6 1 2
temperature desorption peak at 449°C, achieving a marked
enhancementintheC H selectivitybystrengtheningCOadsorption.
2 4
Next,wedecoupledthekineticmechanismsoftheC–Ccoupling
pathwaybyusingareactantsubstitutionstrategycombinedwithdif-
fuse reflectance infrared Fourier transform spectroscopy (DRIFTS).
Under constant H O dosage (1mL), when the reaction system was
2
converted from CO /H O to CO/H O by substituting CO with an
2 2 2 2
equimolaramountofCO,theC H selectivitymarkedlyincreasedfrom
2 4
74.3% to 89.7%, whereas an equimolar CH system completely sup-
4
pressedC H production(SupplementaryFig.45).Thisdemonstrates
2 4
that CO undergoes reversible adsorption-activation on the catalyst
surfaceandservesasthekeyC intermediateforC–Cbondformation,
1
whereasCH isexcludedfromthecouplingnetworkbecauseofitslack
4
ofeffectiveadsorptionanddissociationpathways.

UsingacustomDRIFTSspectrometer(SupplementaryFig.46),we
monitoredthereal-timeevolutionofintermediatesonRu Cu/CeO
0.6 1 2
under concentrated solar irradiation (AM 1.5G (5000mW·cm−2))
(Fig. 4e). During the initial phase of the CO /H O reaction, signals
2 2
emergedat1211and2017cm−1,whichcorrespondtoactivated*COOH
species(derivedfromCO activation)andadsorbed*COspecies(the
2
key reaction intermediate)28,29, respectively. Concurrently, *CH OH
3
(1868cm−1)and*CH OH(1746cm−1)signalswereobserved,whichare
2
associatedwiththeCH synthesispathway30.ThecriticalC H -forming
4 2 4
intermediates,*COCHO(1586cm−1)and*COCH O(1314cm−1),andthe
2
final product, *C H (1449cm−1), emerged at 30 min31. Notably, this
2 4
timecorrespondstothetimeatwhichtheCu0–Cu1+heterointerface
formed, as confirmed by in situ XPS (Fig. 3f). This strict temporal
coupling between the formation of C–C coupling intermediates
and interfacial reconstruction demonstrates that the O -mediated
2
dynamic interfacial restructuring effectively reduces the energy
barrierforC–Ccoupling,therebyenablingpreciseregulationofthe
C H synthesis pathway. Furthermore, the Ru Cu/CeO catalyst
2 4 0.6 1 2
surface showed characteristic vibrational modes for surface-bound
*OH radicals (3568, 3627, and 3648cm⁻1) and dissociative H O
2
adsorptionviaʋ(O–H)stretches(3670,3701,and3734cm⁻1;Supple-
mentary Fig. 47). These signatures confirm hole-mediated H O dis-
2
sociation pathway that supplies protons for CO reduction
2
(SupplementaryFigs.48and49).

Real-timeDRIFTSanalyseswerealsoconductedinCO/HOand
2
CH /HO atmospheres instead of CO /HO. For the CO/H O system
4 2 2 2 2
(Fig.4f),twoadsorbed*COstates(2006and2078cm−1)andabroad-
range*COCHOintermediatesignature(1586cm−1)wereobserved.The
splittingofthe*COadsorptionstatessuggestsarestructuringofthe
catalystsurface’selectronicstate,substantiallyenhancingthesurface
mobility and coupling probability of C intermediates32. Sustained
1
peakbroadeningofthe*COCHOintermediatesignaturewasdetected
asearlyas10minintothereaction,comparedwith30minintheCO /
2
H O system. This CO-induced rapid interfacial restructuring further
2
confirms that CO, as a reactant, substantially accelerates C H pro-
2 4
duction.FortheCH /HOsystem(Fig.4g),themainvibrationalsig-
4 2
naturewasofCH (1306cm−1).Smallpeaksof*CH (1436cm−1),*CH
4 2 3
(1420cm−1),andC–Ccoupling(876cm−1)werealsoobserved,buttheir
intensitiesdidnotchangeovertime33,34.Thisobservationrevealsthe
dualkineticconstraintsforCH moleculesontheRu Cu/CeO sur-
4 0.6 1 2
face;itneitherachievesC–Hbondactivationviaeffectiveadsorption
togenerateessentialcarbonintermediatesnorovercomestheenergy
barriertosurfacemigrationnecessarytodriveC–Ccoupling.TheC H
2 4
selectivityenhancementobservedinthepreliminaryexperimentsand
spectroscopic evidence collectively complete the mechanistic
validationloop.

Mechanisticinvestigations
Bycomprehensivelyconsideringthemultimodalelectronicstructure
analysis,thermodynamicevaluations,andkineticresults,weeluci-
datedthemechanismsforregulatingtheC–Ccouplingselectivityin
theRu Cu(Cu0–Cu1+)/CeO system.Differentialchargedensitydis-
0.6 1 2
tributionforloadingtheRu/CuclusterontheCeO substrateshowsan
2
obviouselectrontransferfromtheclustertoCeO (Fig.5a).However,
2
Baderchargeanalysisrevealsthat,priortoO adsorption,theaverage
2
chargeofthe10CuatomsintheloadedRu/Cuclusteris11.00e−.This
closelymatchesthechargeofelementalCu(11.00e−),therebycon-
firmingthattheCuatomsretaintheirzero-valentstate.Notably,this
unique electronic conservation originates from the Ru atoms func-
tioningasanelectronbufferattheinterface,whichdonate1.64e−to
latticeO,whileadjacentRusingle-atomsitescontribute1.60e−tothe
substrate. This gradient electron donation mechanism effectively
shieldstheCuactivesitesfromdirectelectronicinteractionswiththe
strongly oxidative substrate, thereby maintaining the metallic char-
acteroftheCuclusters.

We performed potential energy surface scans of various O
2
adsorptionconfigurationsonthealloycluster(SupplementaryFig.50)
to identify the lowest-energy state. It is found that the O molecule
2
prefers to bind to the Ru and Cu bimetallic sites with the lowest
adsorption energy (ΔE ) of −4.33eV. Following the adsorption, sig-
ads
nificant charge redistribution occurs within the cluster (Fig. 5b). The
average charge ofthe10Cu atomsdecreases from11.00to10.71e−,
correspondingtoanoverallelectronlossof2.77e−.TheRuatomsinthe
alloyandtheadsorbedOatomsgain+0.81and+1.95e−,respectively.
Theconservationofcharge[ΔQ (−2.77)≈ΔQ (+0.81)+ΔQ (+1.95)]
Cu Ru O
indicates that the adsorption of O does not affect the interaction
2
betweentheclusterandthesubstrate.Next,weconductedanelectro-
negativitygradientanalysis(Cu:1.9<Ru:2.2<O:3.44)toelucidatethe
thermodynamicdrivingforcesforchargetransfer.Twopathwayswere
identified:(1)localizedelectronmigrationinducedbydirectpolariza-
tionoftheCu–Obond,and(2)aCu→Ru→O(AdsorbedO)cascade
transportpathway mediated by interfacial interactions. Dynamic evo-
lution of the Bader electronic structures further corroborated this
mechanism;O-coordinatedRuatomsretaintheirelectronrelayfunction
while undergoing a 0.39 e− loss35–38. This establishes a coupled
mechanismcomprisingthree interfacialinteractions:(i)directcharge
transferviaCu–Ocovalentinteractions,(ii)interfacialelectrontransport
through Cu–Ru metallic bonds, and (iii) secondary electron supply
governedbyRu–Ocoordinationbonds.Theseinteractionscollectively
formahierarchicalCu→Ru→Oelectrontransportpathway.

TheelectronredistributioncausedbyO adsorptionleadstothe
2
coexistenceof0and+1oxidationstatesforCuatomsonthesurfaceof
thealloycluster(Fig.5c),whichiscrucialfortheC–Ccouplingduring
thecatalyticprocess.TheCu7,Cu8,andCu10sites,whicharelocated
atthesurfaceoftheO -mediatedalloycluster,wereconsideredforthe
2
adsorptionoftheintermediatesduringthereaction.Itisfoundthat
Cu8,whichisinthe0-oxidationstateandnotdirectlybondedtoO,
exhibitsadistinctthermodynamicadvantageforboththeadsorption
of CO and the formation of the key intermediate *CO (Fig. 5d–e).
2
Afterwards, multiple pathways were considered (Fig. 5f). Both the
formation of *COH through O-terminal protonation and the direct
desorption of CO encounter high energy barriers (ΔG=1.55 and a
2
1.02eV,respectively).Incontrast,*COCOcanbeformedthroughan
exothermic reaction (ΔG=−0.48eV),driven bythe dual-sitecombi-
nationofCuwithanoxidationstateof0(Cu10)and+1(Cu7).However,
itsgeometricconfigurationisnotconducivetoC–Cbondcoupling,
leadingtoahighenergybarrier(ΔG=1.27eV)for*CHOCOformation.
The optimum pathway for C–C bond coupling is *CO → *CHO →
*CHOCO,withthesequentialΔGvaluesof0.61and0.18eV(Supple-
mentaryFig.51).Theseresultsdemonstratetheplausibilityofthe*CHO
intermediate-dominatedC–Ccoupling.Thehydrogenationof*CHOCO
to form *CH OCO exhibits a lower ΔG of 0.33eV than *CHOCHO,
2
indicatingthefavorto*CH OCOformation.Thisisstronglycorrobo-
2
rated by the stable *CH OCO species observed via in situ DRIFTS
2
analysis.

In *CH OCO, the 0-oxidation-state Cu10 and +1-oxidation-state
2
Cu7arebondedtoOandC,respectively,duetotheirdifferentelec-
trophilicitycharacters.Asaresult,abifurcationofthereactionpath-
wayistriggered(Fig.5g–h).InRoute1,HpreferentiallyattackstheCu-
coordinatedOatomin*CH OCO(ΔG=−0.38eV),butthesubsequent
2
hydrogenationof*CH OHCOattheO-terminusencounteranenergy
2
barrier (ΔG=0.61eV), which is also the rate-limiting step (RDS) of
Route1.Incontrast,Route2isinitiatedviaanHattackatthedistalO
atomoftheterminalCOgroupin*CH OCO.Thissiteexhibitsreduced
2
nucleophilicityduetoitsindirectbondingwiththeCusubstrateand
thus has a positive ΔG of 0.31eV. Furthermore, the subsequent
hydrogenation steps are thermodynamically spontaneous (ΔG=−
0.66eV),drivingthereaction.Notably,duetothesignificantlylowfree
energyofthe*CH OCHintermediate,theformationof*CH OHCHhas
2 2
asecond-highestΔGof0.46eV,thusservingastheRDSofRoute2.The
relatively lower RDS indicates the higher reaction rate of deep
hydrogenationthroughRoute2.

Buildingonanin-depthanalysisofthephotothermalCO reduc-
2
tiondynamicmechanism,werevealspatiotemporallyorderedrecon-
structionofactiveinterfacesintheRu Cu(Cu0–Cu1+)/CeO system
0.6 1 2
(Fig. 6). During the initial irradiation phase (t<30min), lattice-
anchored single-atom Ru sites establish strong electronic metal-
supportinteractionsviaatrigonalprismaticcoordinationconfigura-
tion,acceleratingH Odissociationkinetics.Generated*Hmigratesto
2
alloy cluster surfaces, coupling with strongly adsorbed *CO inter-
mediates via protonation; this dominates CH generation. Con-
4
currently, interfacial oxygen accumulates exponentially with time.
Uponexceedingacriticalthreshold,O byproductadsorbontoCu0
2
sitesandacceptsingle-electrontransfertoformsuperoxideradicals.
Subsequent O–O bond cleavage yields reactive atomic oxygen,
which oxidizes Cu0 to Cu1+ via charge transfer. This transformation
induces selective oxidative etching and atomic rearrangement
onRuCualloysurfaces,drivingself-assemblyofadynamicCu0–Cu1+
heterointerfacewithelectrongradientdistribution.Thisrestructured
interfaceshifts*COintermediatefromlineartobridgingadsorption,
redirecting products toward C products. In the deep reaction
2
phase(30≤t<120min),accumulated*CHOCOintermediatesstabilize
viadual-sitechelation:carbonylcarboncoordinatesCu1+,whilealde-
hyde oxygen binds adjacent Cu0 sites. This spatially confined
adsorption reduces the *CHOCO → *CH OCO hydrogenation barrier,
2
dynamically regulates intermediates coverage, and suppresses
competing side-reaction pathways. Collectively, this dynamic
mechanism shows how the photothermal coupling effect can
controltheproductselectivitybyregulatingactivesites,bothspatially
andtemporally,aswellasthedistributionofkeyintermediates.

Methods
Materialsandreagents
Allchemicalreagentswereobtainedcommerciallyandusedwithout
furtherpurification.Cerium(III)nitratehexahydrate(Ce(NO ) ·6H O,
3 3 2
99.95%),sodiumhydroxide(NaOH,ARgrade),ruthenium(III)chloride
hydrate(RuCl ·xHO,≥99.95%),copper(II)chloride(CuCl ,≥99.99%)
3 2 2
andethyleneglycol(C H O ,≥99.8%)werepurchasedfromAladdin
2 6 2
ReagentCo.,Ltd.Certifiedstandardgasmixtures(CO /N =1:99v/v;
2 2
CH /N =1:99v/v;CO/N =1:99v/v)weresuppliedbyNanjingShang-
4 2 2
yuanIndustrialGasPlant.Ultrapurewater(18.2MΩ·cmresistivity)was
usedforallaqueoussolutionpreparations.

PreparationofcatalystsCeO
2
TheCeO catalystwassynthesizedthroughasolvothermalmethod.In
2
a typical procedure, 1g of Ce(NO ) ·6H O was dissolved in 60mL
3 3 2
deionized water under magneticstirring (600rpm)for1h. Simulta-
neously,8gNaOHwasdissolvedin30mLdeionizedwaterwithiden-
ticalstirringconditions.TheNaOHsolutionwasthenaddeddropwise
(3mL·min−1)intotheCe(NO ) ·6H Osolution,maintainingcontinuous
3 3 2
stirring (600rpm) for 2h to facilitate formation of a Ce(OH) pre-
cursorsuspension.Theresultingmixturewastransferredtoa100mL
PTFE-linedstainless-steelautoclaveandsolvothermaltreatedat180°C
for 12h. After cooling to room temperature naturally, the resulting
precipitatewascollectedbyvacuumfiltration,thoroughlywashedwith
deionizedwater(3×30mL),thendriedundervacuumat70°Cfor12h.
Finally,theobtainedprecursorwasthermallyannealedinatubefur-
naceunderflowingAratmosphere(50mL·min−1)usingatemperature-
programmedprocess:Thetemperaturewaselevatedfromambientto
400°Cataramprateof5°C·min−1,followedbyisothermalholdingat
400°Cfor6h.

PreparationofcatalystsRu /CeO
x 2
TheRu/CeO catalystwith0.6wt%Ruloadingwassynthesizedthrough
2
a solvothermal method. In a typical procedure, 800mg of pre-
synthesized CeO support was first uniformly dispersed in 30mL
2
ethylene glycol using magnetic stirring at 600rpm for 1h. Subse-
quently, 13mg of RuCl ·xH O was added to achieve the target Ru
3 2
loading, followed by continuous stirring (600rpm) for 12h. The
homogeneoussuspensionwasloadedintoa50mLPTFE-linedstain-
less-steelautoclaveforsolvothermaltreatmentat160°Coveraperiod
of28h.Afternaturalcoolingtoroomtemperature,thesolidproduct
was separated via vacuum filtration and rinsed exhaustively with
deionizedwater(usingtwo15mLaliquots),thendriedundervacuum
at 70°C for 12h. Finally, the obtained precursor was thermally
annealedinatubefurnaceunderflowingAratmosphere(50mL·min−1)
usingatemperature-programmedprocess:Thetemperaturewasele-
vatedfromambientto600°Cataramprateof5°C·min−1,followedby
isothermal holding at 600°C for 2h. Catalysts with different Ru
loadings(0.1,0.3,0.9,1.2wt%)werepreparedfollowinganidentical
proceduretothatdescribedfortheRu /CeO catalyst,withprecise
0.6 2
adjustmentoftheRuCl ·xH O.
3 2

PreparationofcatalystsCu /CeO
x 2
TheCu/CeO catalystwith1wt%Culoadingwassynthesizedthrougha
2
solvothermal method. In a typical procedure, 800mg of pre-
synthesized CeO support was first uniformly dispersed in 30mL
2
ethylene glycol using magnetic stirring at 600rpm for 1h. Subse-
quently,18mgofCuCl waspreciselyaddedtoachievethetargetCu
2
loading, followed by continuous stirring (600rpm) for 12h. The
homogeneoussuspensionwasloadedintoa50mLPTFE-linedstain-
less-steelautoclaveforsolvothermaltreatmentat160°Coveraperiod
of28h.Afternaturalcoolingtoroomtemperature,thesolidproduct
was separated via vacuum filtration and rinsed exhaustively with
deionizedwater(usingtwo15mLaliquots),thendriedundervacuum
at 70°C for 12h. Finally, the obtained precursor was thermally
annealedinatubefurnaceunderflowingAratmosphere(50mL·min−1)
usingatemperature-programmedprocess:Thetemperaturewasele-
vatedfromambientto600°Cataramprateof5°C·min−1,followedby
isothermal holding at 600°C for 2h. Catalysts with different Cu
loadings(0.6,0.8,1.2,1.4wt%)werepreparedfollowinganidentical
procedure to thatdescribed for the Cu/CeO catalyst, with precise
1 2
adjustmentoftheCuCl .
2

PreparationofcatalystsRu Cu /CeO
x y 2 2
The RuCu/CeO catalyst with nominal loadings of 0.6wt% Ru and
2
1.0wt% Cu was synthesized through a solvothermal method. In a
typicalprocedure,800mgofpre-synthesizedCeO supportwasfirst
2
uniformlydispersedin30mLethyleneglycolusingmagneticstirring
at600rpmfor1h.Subsequently,13mgRuCl ·xH Oand18mgCuCl
3 2 2
were co-introduced stoichiometrically to achieve the target metal
loading, followed by prolonged stirring (600rpm, 12h) to ensure
homogeneity.Thewell-dispersedsuspensionwashermeticallysealed
ina50mLPTFE-linedstainless-steelautoclaveforsolvothermaltreat-
ment at 160°C for 28h. After natural cooling, the precipitate was
retrieved by vacuum filtration, washed sequentially with deionized
water(2×15mL),anddriedundervacuumat70°Cfor12h.Finally,the
obtainedprecursorwasthermallyannealedinatubefurnaceunder
flowing Ar atmosphere (50mL·min−1) using a temperature-
programmed process: The temperature was elevated from ambient
to600°Cataramprateof5°C·min−1,followedbyisothermalholding
at600°Cfor2h.CatalystswithvaryingRu:Cumassratios(1:3,1:1,5:3,
3:1)weresynthesizedusingthesameimpregnationprotocolemployed
fortheRu Cu/CeO catalyst,withcontrolledvariationofRuCl ·xH O
0.6 1 2 3 2
andCuCl precursorconcentrations.
2

PreparationofcatalystsRu Cu(Cu0–Cu1+)/CeO
0.6 1 2
TheRu Cu(Cu0–Cu1+)/CeO catalystwassynthesizedthroughinsitu
0.6 1 2
activation during photo-thermal CO /H O co-reduction under con-
2 2
centrated solar irradiation (5000mW·cm−2, AM 1.5G spectrum,
300–2500nm) for 30min in a sealed quartz microreactor (100mL
volume).ThedynamicevolutionofCuoxidationstateswasmonitored
through quasi in situ X-ray photoelectron spectroscopy, revealing
coexistence of metallic Cu0 (918.6–919.4eV) and oxidized Cu1+
(913.4–913.9eV)asshowninFig.3f.Thisdual-stateCuconfiguration
informed the systematic nomenclature Ru Cu(Cu0–Cu1+)/CeO ,
0.6 1 2
where subscripts denote nominal metal loadings (wt%) and super-
scriptsindicatequantifiedoxidationstates.

PreparationofcatalystsCuO/CeO
2
The CuO/CeO catalysts were synthesized using a glycerol-assisted
2
hydrothermalmethodfollowedbycalcination.Specifically,1.5mmol
ofCu(NO ) ·3HOand1.0mmolofCe(NO ) ·6H Oweredissolvedin
3 2 2 3 3 2
40mLofanaqueoussolutioncontaining2.3Mglycerolwithvigorous
stirringatroomtemperature.Theresultingsolutionwasloadedintoan
autoclaveconstructedofstainlesssteelandfeaturingaTeflonliner.
Thisassemblywassubjectedtoahydrothermalreactionat180°Cfora
duration of 6h. Upon cooling to room temperature, the solid pre-
cipitatewasisolatedthroughcentrifugationandsubsequentlyrinsed
multipletimeswithanhydrousethanol(≥3times).Theprecipitatewas
driedat80°Cfor12hundervacuum.Thedriedprecursorwasthen
calcined in static air using a muffle furnace. The temperature was
rampedto350°Cat5°C·min−1andheldfor2h,yieldingthefinalCuO/
CeO catalyst.
2

PreparationofcatalystsRuSAs+CuSAs/CeO
2
TheRuSAs+CuSAs/CeO catalystwassynthesizedviaimpregnation-
2
calcination. First, 800mg of pre-synthesized CeO supportwas dis-
2
persedin30mLofdeionizedwaterundermagneticstirring(600rpm)
for1h.Subsequently,13mgofRuCl ·xH Oand18mgofCuCl were
3 2 2
addedtoachievetargetmetalloadings,withstirring(600rpm)con-
tinued for 12h to ensure thorough precursor adsorption. The pre-
cursor solution was vacuum-dried at 70°C for 12h. The precursor
underwent temperature-programmed reduction in a tube furnace
under 50mL·min−1 of high-purity 5% H /Ar: heating from 25°C to
2
400°C at 5°C·min−1, then holding at 400°C for 2h to form highly
dispersedsingle-atomsites.Aftercoolingtoroomtemperatureunder
Ar,thesamplewascollectedforuse.

PreparationofcatalystsRuSAs+Cusub-nanocluster/CeO
2
TheRuSAs+Cusub-nanocluster/CeO catalystwassynthesizedvia
2
impregnation-calcination.First,800mgofpre-synthesizedCeO sup-
2
portwasdispersedin30mLofdeionizedwaterundermagneticstir-
ring(600rpm)for1h.Subsequently,13mgofRuCl ·xH Oand90mg
3 2
of CuCl wereadded to achieve target metalloadings,with stirring
2
(600rpm)continuedfor12htoensurethoroughprecursoradsorp-
tion.Theprecursorsolutionwasvacuum-driedat70°Cfor12h.The
precursor underwent temperature-programmed reduction ina tube
furnaceunder50mL·min−1ofhigh-purity5%H /Ar:heatingfrom25°C
2
to500°Cat5°C·min−1,thenholdingat500°Cfor2htoformhighly
dispersedsingle-atomsites.Aftercoolingtoroomtemperatureunder
Ar,thesamplewascollectedforuse.

Characterizations
High-resolution TEM (HRTEM) imaging and energy-dispersive spec-
troscopy(EDS)elementalmappingwereperformedonaTalosF200X
system(ThermoFisherScientific).Field-emissionSEM(FESEM)char-
acterizationwasconductedusinganApreoSLoVac(ThermoFisher
Scientific).HAADF-STEMandatomic-resolutionimagingwerecarried
out on a Titan Cubed Themis 60–300 microscope (Thermo Fisher
Scientific) operated at 300kV with a probe aberration correction.
X-ray absorption spectroscopy measurements including X-ray absorption
near-edgestructure(XANES)andextendedX-rayabsorptionfinestruc-
ture(EXAFS)atbothRuK-edge(22117eV)andCuK-edge(8979eV)
were acquired at the 14W beamline of the Shanghai Synchrotron
RadiationFacility(SSRF).ASi(311)double-crystalmonochromatorwas
employed for energy selection, with reference standards (Ru foil,
RuO ,Cufoil,Cu O)usedforenergycalibration.Allspectrawerere-
2 2
cordedintransmissionmodeatambienttemperatureandprocessed
usingtheAthenasoftwarepackage.XPSanalysiswasperformedonan
ESCALAB 250Xi spectrometer (Thermo Scientific) with monochro-
matic Al Kα radiation (1486.6eV). UV-Vis DRSwereobtainedusinga
UV-2450spectrophotometer(Shimadzu)withanintegratingsphere.
Thermal analysis included simultaneous TGA-DSC (SDT Q600, TA
Instruments) under N (10°C·min−1, 25–520°C).TPDexperiments
2
(CO /CO/O/H O)wereconductedonanAutoChemII2920system
2 2
(Micromeritics)withTCDdetection.Operando diffuse reflectance
infrared Fourier transform spectroscopy measurements were con-
ducted using a Bruker TENSOR II spectrometer coupled with a
custom-builtsolarconcentratorreactorsystem.Temperaturemonitor-
ing was achieved through combined thermocouple measurements
andinfraredthermographyusinganFLIRA65sc camera.

Quasi-insituXPS
Ru Cu/CeO samples(50mgpertimepoint)wereirradiatedunder
0.6 1 2
concentrated solar light (AM 1.5G spectrum; 5000mW·cm−2) using
a PerfectLight PLS-SXE 300/300UXE solar simulator. Reactions
occurred in a 1vol% CO /N (99.999%) atmosphere with 1mL H O
2 2
for 0, 15,30, 60, and 120min. Post-irradiation, samples were trans-
ferred to an N glovebox, homogenized with 10mg of spectro-
2
scopically pure graphite powder (<20μm particle size) in an agate
mortartomitigatechargingeffects,anddenselypackedintoasample
holder.XPSspectrawereacquiredatroomtemperatureinaThermo
Scientific ESCALAB 250Xi spectrometer (base pressure ≤ 5×10−8
mbar).Allbindingenergieswerecharge-correctedandreferencedto
thegraphiteC1speakat284.8eV,ensuringcross-comparabilityacross
thebatch.

OperandoDRIFTS
In an operando DRIFTS system (Bruker TENSOR II spectrometer)
equippedwithahigh-temperature,high-pressurediffusereflectance
cell, 50mg of Ru Cu/CeO catalyst powder was dispersed on a
0.6 1 2
spectroscopic-gradeIR-transparentwindow.Thesamplewaspurged
in situ with high-purity (UHP) N (≥99.999%, 50 sccm) at 25°C for
2
30mintoremovephysicallyadsorbedimpuritiesandmoisture;base-
linestabilitywasconfirmedbyreal-timeIRmonitoring.Thegasflow
was then switched to a reaction mixture of CO /N balanced gas
2 2
(controlledbycalibratedmassflowcontrollers,MFCs)co-fedwithH O
2
vapor(viaabubbler).Allstreamswerepremixedinheatedtransfer
linesbeforeenteringthecell.Uponintroducingthereactiongasand
activatingthesolarsimulator(PerfectLightPLS-SXE300/300UXEAM
1.5Gspectrum;5000mW·cm−2)simultaneously—definingt=0minas
the reaction start—collimated irradiation was delivered through the
cell’stopwindowontothecatalystviaaFresnellensfocusingsystem
(focallength:30cm).OperandoDRIFTSdataacquisitioncommenced
immediately using the stabilized N -purged spectrum as the back-
2
groundreference,collectingsingle-beamspectraat4cm−1resolution
with256co-addedscanspermeasurement.Absorbancespectrawere
recorded at t=0,15,30,45, 60,90,and 120min under continuous
reaction/irradiationtotracksurfaceintermediateevolution.

DetailsofthephotothermalcatalyticCO reduction
2
Photothermal catalytic CO reduction was performed in a custom-
2
designedstainless-steelreactor(100mL)equippedwithaquartzwin-
dowandFresnellensoptics(30cmfocallength),integratedwithasolar
simulator(PLS-SXE300/300UXE,PerfectLight)providingcalibratedAM
1.5Girradiation(5000mW·cm−2).Priortothereaction,thesystemwas
purged with N (99.999%, 50mL·min−1, 10min) followed by charging
2
withCO/N mixture(1vol%,Praxair).Watervaporwasintroducedby
2 2
injecting deionized water quantitatively(1mL,18.2MΩ·cmresistivity)
viaagas-tight syringe.Duringthereaction,thefocusedlightspotgen-
eratedsimultaneousphotoexcitationandlocalizedthermaleffectson
the catalyst surface, enabling photothermal synergistic catalysis. Gas-
eousproductswereanalyzedonlineandquantifiedusinggaschroma-
tograph(GC-8860)withthermalconductivitydetector(TCD)andflame
ionizationdetector(FID),employingaPorapakQpackedcolumn.All
gaseouscomponentswerequantifiedviamulti-pointcalibrationusing
NIST-traceablestandards(calibrationcurvesexhibitedlinearcorrelation
coefficientsR2>0.999).Thecatalystwascontinuouslyirradiatedfor2h
with periodic sampling. Dark controls and additional control experi-
mentswereconductedconcurrentlytorigorouslyexcludebackground
interferenceandverifyresultreliability.

PhotocatalyticH O production
2 2
Afterphoto-thermalcatalyticCO reduction,30mLhigh-puritydeio-
2
nizedwater(18.2MΩ·cm)wasinjectedthroughthereactor’sinjection
port. A low-temperature circulator (5.0±0.1°C) minimized thermal
degradationofH O .Componentsadheringtoreactorwallswerefully
2 2
dissolved in the aqueous phase by vortex mixing (200rpm, 3min),
ensuringquantitativeproductrecovery.H O concentrationwasthen
2 2
quantifiedviastandardizediodometrictitration.

MeasurementofH O concentration
2 2
H O concentrationwasdeterminedusingastandardizediodometric
2 2
method39.Briefly,1mL0.1Mpotassiumhydrogenphthalate(C HKO )
2 8 5 4
aqueoussolutionwasaddedtothesample,followedby1mLof0.4M
potassiumiodide(KI)aqueoussolution.Aftera30minreactionper-
iod, H O reacted with iodide anions (I−) under acidic conditions
2 2
according to the reaction: H O +3I−+2H+ → I −+2H O, producing
2 2 3 2
triiodide anions (I −) that exhibit strong absorption at 350nm. I −
3 3
concentration was quantified using UV-Vis spectroscopy, allowing
calculationoftheH O concentrationgenerated.
2 2

DetailsofthethermocatalyticCO reduction
2
Theperformanceoftheas-preparedcatalystwasevaluatedinafixed-
bed stainless steel reactor. The temperature error at the catalyst
location was controlled within ±5°C. The catalytic evaluation was
performed inthe reaction temperaturerange of 200–600°Cunder
CO /H O gas flow. All gas flows were achieved by precision-
2 2
calibrated mass flow controllers. Product analysis was performed
via online gas chromatography using a thermal conductivity detector-
equipped system with a packed column40. Post catalytic evaluation
was performed via online gas chromatography. Product selectivity
was investigatedunderidenticalconditionswithvaryingtemperatures.

Solar-to-chemicalenergyconversionefficiency
The solar-to-chemical energy conversion efficiency (STC) could be
expressedastheratioofoutputtoinputenergy,calculatedbyref.41:
η = (qm J(cid:1)mol (cid:3)1(cid:1)mol J) / (IAt W(cid:1)cm(cid:3)2(cid:1)cm2(cid:1)s W(cid:1)s) ×100%
STC
WhereqisthecombustionheatvalueofCO(q CO =283×103J(cid:1)mol (cid:3)1),
CH 4 (q CH4 =890:31×103J(cid:1)mol (cid:3)1)andC 2 H 4 (q C2H4 =1411×103J(cid:1)mol (cid:3)1),
mdenotethemoleofproducedCO,CH 4 andC 2 H 4 (mol),Idenotethe
lightintensity(W·cm−2),Aistheirradiationarea(cm2),andtdenotethe
reaction time (s). Thus, the solar-to-chemical energy conversion
efficiency for the Ru 0.6 Cu 1 (Cu0–Cu1+)/CeO 2 catalyst was calculated
tobe0.50%.

Productselectivitycalculation
TheproductselectivityforCO 2 conversiontoCO,CH 4 andC 2 H 4 were
calculatedusingthefollowingequation42:
ProductselectivityofC H (%)=½n(C H )(cid:4)=½n(C H )+n(CH )+n(CO)(cid:4)×100%
2 4 2 4 2 4 4
ProductselectivityofCH (%)=½n(CH )(cid:4)=½n(C H )+n(CH )+n(CO)(cid:4)×100%
4 4 2 4 4
ProductselectivityofCO(%)=½n(CO)(cid:4)=½n(C H )+n(CH )+n(CO)(cid:4)×100%
2 4 4
wheren(CH ),n(CH )andn(CO)aretheamountsofproducedC H ,
4 4 2 4
CH andCO.
4

Electronselectivitycalculation
Electronselectivitywascalculatedbasedontheconsumptionof2,2,8
and 12 electrons per H , CO, CH and C H molecule, respectively,
2 4 2 4
accordingtothefollowingformulas43:
Sel (H ) = (2×n(H )) / (2×n(H )+2×n(CO)+8×n(CH )+12×n(C H )) ×100%
electron 2 2 2 2 4 2 4
Sel (CO) = (2×n(CO)) / (2×n(H )+2×n(CO)+8×n(CH )+12×n(C H )) ×100%
electron 2 2 4 2 4
Sel (CH ) = (8×n(CH )) / (2×n(H )+2×n(CO)+8×n(CH )+12×n(C H )) ×100%
electron 4 4 2 2 4 2 4
Sel (C H ) = (12×n(C H )) / (2×n(H )+2×n(CO)+8×n(CH )+12×n(C H )) ×100%
electron 2 4 2 4 2 2 4 2 4
Wherenrepresentsthemolaryieldofeachproduct.

DFT-basedcomputationalframeworkforsurfaceadsorption
energeticsandreactionthermodynamics
Alldensityfunctionaltheorycomputationswereperformedusingthe
ViennaAbInitioSimulationPackage(VASP)44–46.Two-dimensionalslab
surfacesweremodeledwithperiodicboundaryconditions,incorporat-
inga20Åvacuumlayertominimizeinter-slabinteractions.Samplingof
theBrillouinzonewasconductedusingaMonkhorst-Packk-pointmesh
of3×3×147.Theelectronicstructurecalculationsemployedprojector-
augmented-wave (PAW) pseudopotentials combined with Perdew-
Burke-Ernzerhof (PBE) exchange-correlation functionals48–50. Plane-
wave basis sets with a kinetic energy cutoff of 500eV described the
electronic wavefunctions. Self-consistency convergence was achieved
whensuccessiveiterationenergiesdifferedbylessthan10−5eV.Struc-
turalrelaxationsappliedtheconjugate-gradienttechnique51,continuing
until all Hellmann-Feynman force components were below 10−2 eV/Å.
These DFT-derived conclusions require cautious interpretation given
inherentchallengesinmodelingtheexactcatalyststructureandreactive
environmentunderoperandoconditions;fundamentallimitationsarise
from approximate exchange-correlation functionals inherent to DFT,
whichfailtofullycapturecomplexelectronicbehaviors.
Gibbsfreeenergychange(G)ofeachchemicalreactionstepwas
calculatedby:
G=E +E (cid:3)TS
DFT ZPE
whereE ,E ,T,andS denotetotalenergyobtainedfromDFT,
DFT ZPE
zero-point energy, temperature, and entropy, respectively. The
temperature was set as room temperature, i.e. 298.15K. The zero-
point energy and entropy were calculated in VASPKIT code50.
AdsorptionenergyΔE onthesurfaceofsubstrateswasdefinedas:
ad
ΔE =E (cid:3)(E +E )
ad *mole * mole
whereE *mole ,E * ,andE mole denoteenergiesoftheadsorbedmolecule
onsubstrates,thebaresubstrates,andthemolecule.
Theformationenergy(E)isdefinedas
f
E =E (A B ) (cid:3)xE (cid:3)yE
f x y A B
whereE(A x B y )referstotheenergyoftheA x B y clusters.E A andE B refer
theenergyperatomofAbulkandBbulk,respectively.Thesmallerthe
formation energy, the easier it is to form, and the more stable the
structure.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "I've eagerly read the work by Ren et al. as they delve into a very relevant topic, oxygen-induced reconstruction of Cu ensembles toward the generation of ethylene via CO2 photoreduction. I am myself not a expert in photocatalysis, as I've been working mainly on CO2 electroreduction, yet I found the reported ethylene yield considerable. Thus in my opion the approach is interesting and the results meaningful. Before granting publication, though, the authors should clarify some aspects and prevent some potential flaws. Below my detailed questions.\n(1) A reaction scheme in the supporting information highlighting all the reactions occurring on the RuCu/CeO2 catalyst is desirable. In fact, the authors claim that water dissociation leads either to O2 formation or formation of adsorbed *H. As an electrochemist, it is not clear to me whether for water dissociation the authors means water reduction (which generates H2 and OH-, requiring electrons in) or oxygen evolution (which generates O2 and proton-electron couples, being though an oxidation reaction).\n(2) Following up the previous question, are oxygen evolution and CO2 reduction competing for the same active site in the process? Besides, once the O2 is formed, will be reduce via the Oxygen Reduction Reaction? If this is the case, this will further compete with CO2 reduction, being another electron sink.\n(3) Besides these general questions, how are the formation energies in Fig. 1f calculated? Which reference energies (bulk metal or?) and equations were used?\n(4) If I undertand correctly molecular dynamics were carried out on a water/CO2/catalyst interface to demonstrate water aggregation on clean CeO2 (see Fig. S28). I wonder whether these simulations are actually meaningful, as water changes from liquid to gas moving beyond 100 degrees celsius.", "reviewer_2": "This work reports a Ru₀.₆Cu₁(Cu⁰-Cu⁺)/CeO₂ catalyst constructed through an O₂-mediated dynamic interface reconstruction strategy for photothermal catalytic CO₂ reduction to ethylene (C₂H₄). The study utilizes single-atom Ru doping to induce a distorted pentahedral coordination field that accelerates H₂O dissociation, and triggers O₂-driven self-assembly of Cu⁰-Cu⁺ gradient interfaces through the photothermal effect, optimizing *CHOCO adsorption and C-C coupling pathways, thereby addressing catalyst poisoning under high oxygen partial pressure and sluggish C-C coupling kinetics. However, the characterization of single-atom active sites, potential changes in catalyst elemental valence states, and the modulation mechanism of valence states by O₂ require further refinement. Additionally, the writing of the manuscript needs to be clearer and more fluent. Specific comments are as follows:\n1. The background introduction in the Introduction section is insufficient. Compared to the current approach of integrating conclusions from previous related work, the authors need a more complete and independent logical chain to highlight the innovation and starting point of this work.\n2. The description of Fig.1a-1e in the Discussion section reads more like content for the Introduction. Furthermore, the rationale for choosing a Ru single-atom catalyst needs to be explained.\n3. What do Ru0.6Cu1/CeO2 and Ru0.6/CeO2 represent? Please specify upon their first mention. The coordinate state of the single-atom catalysts should be clarified in more detail, for example, with experimental verification of the Ru:Cu 3:5 stoichiometric ratio.\n4. The calculations in Fig. 1 only demonstrate that Ru3Cu5 is the most readily formed stable structure; this cannot be directly used as the reason for influencing the catalyst's product selectivity.\n5. The performance analysis in lines 278-280 and 296-307 does not specify which figure/chart it refers to.\n6. Lines 300-304: More material characterization is needed, rather than speculating about possible valence changes in Cu based solely on performance variations.\n7. Lines 410-418: What does \"replacing CO2/H2O with equimolar CO\" mean? Does it mean replacing CO2? If not, where would the hydrogen source for C₂H₄ come from?\n8. The in-situ characterization does not clearly elucidate the role of O₂ in the Cu⁰/Cu⁺ interface reconstruction.\n9. Does O₂ cause over-oxidation to Cu²⁺ during the oxidation process of Cu?\n10. The discussion on the modulation mechanism by O₂ is lacking.", "reviewer_3": "This work demonstrates an oxygen engineering for activation of Cu0-Cu+ pairs further for the photoreduction CO2 to C2H4. The performance on this configuration shows an impressive activity in the field of C2H4 production from CO2. Moreover, plentiful DFT simulation provides an evident support for the dynamic reconstruction of Cu0-Cu+ pairs hypothesized in this work. This concept is interesting, and the strategy provides a feasible route for the photocatalyst design. However, some concerns should be further clarified prior to published. Specific issues are as follows:\nMajor:\n1. As discussed in XAFs session, the valence state of Ru seems between 0 and +4, as shown in figure 2q and 2r, why the author made the analysis of d-p hybridization by Ru2+? How to make sure +2? The analysis of Ru filed seem upon the octahedral field, is it fitting for the pentahedral? Additionally, similar to Cu+, result shows Cu is metallic state (Cu0), why use Cu+? And if Cu+, the eg is fully filled by the electrons, how to bonding by d-p? If no COHP analysis of individual of d orbitals with p, how to conclude dz2 or dx2-y2 or dxz…?\n2. How to confirm the substitution between Ru and Ce, instead of atomic surface anchor or doping into the lattice of cerium oxides? Any evidence?\n3. Regarding to the in situ XPS analysis in figure 3f, how’s the change of Cu0 and Cu+ species change after remove irradiation? Will recover thermodynamical equilibrium?\n4. For the controlled performance, it’s wired that nothing productivity was obtained by sole UV and thermocatalysis in figure 3d, what’s the reason behind? Particularly under UV, temperature probably will not be up to ~462℃ under UV, alternatively, if keep the system at ~462℃ and then add UV irradiation, what happens?\n5. From the result of 3 W/cm2 in Figure 3, the phenomenon is interesting. What’s the reason or mechanism behind, why 3 W/cm2 is the on-set switch of C2H4 production? If control the reaction system temperature without irradiation at the same as 3 W/cm2, an illumination-progressed (such as 50mW/cm2, 100mW/cm2, 300mW/cm2, et al.) performed under the similar condition, will C2H4 produced?\n6. The configuration of RuxCuy/CeO2 proposed in this work is Ru single atoms with RuCu sub-alloy. How’s performance of the Ru SAs+Cu SAs/CeO2, and Ru SAs+Cu sub-alloy/CeO2?\n7. As the proposed pathway of OER in Figure S12, is there any H2O2 in the solution? What’s the function of holes in the proposed reaction system? How it will happen if some sacrificer (like function for h+ and ·OH quenching) added during CO2RR.\n8. How’s the charge dynamics performance of the photocatalysts?\nMinor:\n1. More details of experiments session should be provided, in particular the in situ techniques including XPS and DRIFTS, more details of experimental procedure should be given clearly.\n2. The author presents 34 district configurations in the figure 1f, the profiles of their energy seem to arrange from less to more following the arrow. And the Ru3Cu5 seems to be highlight. What’s the different configuration in the red dashed box, are they same as Ru3Cu5? If same, what’s the differences among them?\n3. Is there any signal of Cu2+ can be observed at higher binding energy range during the in situ XPS progress?\n4. As the dissociation of H2O for the proton providing, is there any H2 detected?\n5. What’s the specific band structure of catalysts in this work?\n6. What’s the condition for TGA measurement in Figure s25?\n7. What’s the behavior of O2 after activated the Cu species, adsorbed on the Ru-Cu interface and occupied some Ru-Cu sites?", "reviewer_4": "In this work, the authors develop an oxygen-mediated dynamic interfacial reconstruction strategy to fabricate Ru0.6Cu1(Cu0–Cu1+)/CeO2 catalysts with adaptive oxygen tolerance. This approach simultaneously addresses two critical bottlenecks in artificial photosynthesis for CO2-to-hydrocarbon conversion: catalyst poisoning under high oxygen partial pressures and sluggish C2-product formation kinetics. The atomic-scale design features Ru single atoms occupying Ce lattice sites, forming distorted pentahedral coordination fields that facilitate proton-coupled electron transfer and accelerate H2O dissociation. Meanwhile, concentrated solar irradiation induced photothermal effects drive the self-assembly of Cu0–Cu1+ charge-gradient interfaces within Ru/Cu alloy clusters. This interfacial reconstruction optimizes *CHOCO intermediate adsorption behavior and restructures the C–C coupling pathway. These synergistic mechanisms collectively enable superior performance: 549 ± 20 μmol·g–1 ethylene production (74.3% selectivity) with 0.5% solar-to-chemical energy conversion efficiency. This work delivers compelling mechanistic insights into experimental phenomena through comprehensive catalyst characterization, experimental validation, and theoretical calculations. The study is recommended for publication in Nature Communications provided that the following points are addressed to further enhance the clarity and precision.\n1. To emphasize the unique synergistic effects of photothermal coupling in this “thermally assisted photocatalytic system”, we recommend supplementing the study with wavelength-dependent experiments (e.g., 325 nm, 808 nm) to validate the distinctive role of the coupled photothermal mechanism.\n2. The reaction-generated O2 byproduct critically mediates the in situ dynamic reconstruction of Cu0–Cu+ active interfaces. The proposed mechanism explicitly indicates that this O2 primarily originates from the oxidation of H2O molecules (2H2O → O2 + 4H+ + 4e⁻). We recommend that the authors supplement this study with systematic H2O concentration-dependent experiments.\n3. Given the unique operating environment of concentrated solar photothermal catalysis systems, evaluating the Ru0.6Cu1(Cu0–Cu1+)/CeO2 catalyst's tolerance to thermal-induced deactivation is imperative. We recommend supplementing this study with differential scanning calorimetry data for the catalyst.\n4. The in-situ DRIFTS data presented in Figure 4e provide critical evidence for tracking the dynamic evolution of key carbon-based intermediates along the C2H4 formation pathway. The study explicitly identifies H2O as both the reaction medium and the crucial hydrogen source. However, the current spectral analysis primarily focuses on carbon species evolution and does not directly capture concurrent spectroscopic evidence for H2O molecule activation or hydrogen transfer processes. It is strongly recommended that the authors supplement their analysis by presenting the relevant spectral regions associated with H2O evolution and critical hydrogen-containing intermediates from the in-situ DRIFTS data."}, "author_response": "Point-by-Point Responses to Reviewers’ Comments\nReviewer #1:\n“1. I've eagerly read the work by Ren et al. as they delve into a very relevant topic,\noxygen-induced reconstruction of Cu ensembles toward the generation of ethylene via\nCO photoreduction. I am myself not an expert in photocatalysis, as I've been working\n2\nmainly on CO electroreduction, yet I found the reported ethylene yield considerable.\ngranting publication, though, the authors should clarify some aspects and prevent\nsome potential flaws. Below my detailed questions.”\nWe would like to sincerely thank this Reviewer for the positive feedback on our\nmanuscript. To clarify the specific pathway of H O molecule dissociation and its\n2\nrelationship with electron transfer (distinguishing reductive cleavage from oxidative\nO evolution), we have added a detailed reaction schematic. This schematic clearly\n2\nillustrates key reaction steps occurring on the Ru Cu /CeO catalyst surface.\n0.6 1 2\nRegarding the O evolution, reduction processes, and their competitive mechanisms,\n2\nwe further verified these via comparative experiments. For formation energy\ncomputations, we supplemented the methodology with reference state definitions,\ncalculation formulae, and descriptions of all key parameters. Additionally, addressing\nthe Reviewer’s concern about molecular dynamics simulations at gas-liquid interfaces\nunder high-temperature conditions, we clarified our rationale for the temperature\nsettings in the revised text. We have diligently addressed each of these comments in a\npoint-by-point manner and have incorporated additional contents into the revised\nmanuscript and corresponding Supplementary Information.\n“2. A reaction scheme in the supporting information highlighting all the reactions\noccurring on the RuCu/CeO catalyst is desirable. In fact, the authors claim that\n2\nwater dissociation leads either to O formation or formation of adsorbed *H. As an\n2\nelectrochemist, it is not clear to me whether for water dissociation the authors means\nwater reduction (which generates H and OH-, requiring electrons in) or oxygen\n2\nevolution (which generates O and proton-electron couples, being though an\n2\noxidation reaction).”\nWe sincerely thank the Reviewer for this professional comment. Upon photoexciting\nthe Ru Cu /CeO catalyst, spatially separated electron–hole pairs (e⁻–h⁺) form.\n0.6 1 2\nPhotogenerated electrons (e⁻) migrate to reduction sites, driving CO reduction, while\n2\nphotogenerated holes (h+) accumulate at oxidation sites, oxidizing H O molecules. O–\nintermediates (*OH, *O, and *OOH) prior to O evolution. As shown:\n2\n(1) H O + * + h+ → *OH + H+\n2\n(2) *OH + h+ → *O + H+\n(3) *O + H O + h+ → *OOH + H+\n2\n(4) *OOH + h+ → O + H+ + *\n2\n* represents the active site.\nUnder concentrated solar irradiation (AM 1.5G, 5000 mW·cm⁻2), Operando\nDRIFTS analysis of CO /H O co-adsorption revealed in situ formation of\n2 2\nintermediates during 120 min illumination. The Ru Cu /CeO catalyst surface\n0.6 1 2\nshowed characteristic vibrational modes for surface-bound *OH radicals (3568, 3627,\nand 3648 cm⁻1) and dissociative H O adsorption via ʋ(O–H) stretches (3670, 3701,\n2\nand 3734 cm⁻1; Supplementary Fig. 49) (Nat. Commun., 2024, 15, 4675; Nano energy,\n2023, 113, 108578; Angew. Chem. Int. Ed., 2024, 63, e202410474). These signatures\nconfirmed hole-mediated H\n2\nreduction. This evidence validated the kinetic relevance of the four-step H O\n2\noxidation mechanism, as captured through the observed intermediates (Supplementary\nFig. 50). The revised manuscript and Supplementary Information now include\nadditional content, which is distinguished by a yellow background.\nSupplementary Fig. 49 | Operando DRIFTS of H O activation intermediates on\n0.6 1 2\nThe reaction cascade occurs through four concerted steps:\n1. H O adsorption and oxidation:\n2\nhydroxyl species (*OH) while releasing a proton (H+).\n2. Hydroxyl oxidation:\n*OH + h+ → *O + H+\nSubsequent hole oxidation deprotonates *OH, yielding adsorbed atomic oxygen (*O)\nand a H+.\n3. O–O bond formation:\n*O + H O + h+ → *OOH + H+\n2\nadsorbate (*OOH), releasing a third H+.\n4. O liberation:\n2\n*OOH + h+ → O + H+ + *\n2 2\nCleavage of C=O bonds in CO occurs via stepwise electron transport, as\n2\nconfirmed by catalytic performance profiles, Operando DRIFTS studies, and Gibbs\nfree energy calculations (Figs. 3c, 4e). These analyses identify CO, CH , and C H as\n4 2 4\nproducts (Fig. 5g) and explicitly verify intermediate formation, defining the reaction\npathway for CO reduction (Supplementary Fig 51).\n2 2\ndependent evolution rates of CO, CH , C H , and O during photothermal CO\n4 2 4 2 2\nreduction with H O over the Ru Cu /CeO catalyst. Error bars represent standard\n2 0.6 1 2\ndeviations (s.d.) derived from three independent measurements. Data are expressed as\nmean ± s.d.\nFig. 4 | Active site verification and operando characterization of C H -formation\n2 4\nintermediates. e, Operando DRIFTS of CO /H O-derived C–C coupling\n2 2\nintermediates on Ru Cu /CeO .\n0.6 1 2\nFig. 5 | Theoretical calculation and CO reduction mechanism. g, Gibbs free\n2\nenergy diagram for the conversion of H O and CO into *CH CH .\n2 2 2 2\n1. The pathway for CO reduction to CO involves:\n2 2\n*CO + H+ + e⁻ → *COOH\n2\n*COOH + H+ + e⁻ → *CO + H O\n2\n*CO → CO↑ + * or\n2. The pathway for CO reduction to CH involves:\n2 4\nCO + * → *CO\n2 2\n*CO + H+ + e⁻ → *COOH\n2\n*COOH + H+ + e⁻ → *CO + H O\n2\n*CO + H+ + e⁻ → *CHO\n*CHO + H+ + e⁻ → *CH O\n2\n*CH O + H+ + e⁻ → *CH OH\n2 2\n*CH OH + H+ + e⁻ → *CH OH\n2 3\n*CH OH + H+ + e⁻ → *CH + H O\n3 3 2\n*CH + H+ + e⁻ →*CH\n3 4\n*CH → CH ↑ + *\n4 4\n3. The pathway 1 for CO reduction to C H involves:\n2 2 4\nCO + * → *CO\n2 2\n*CO + H+ + e⁻ → *COOH\n2\n*COOH + H+ + e⁻ → *CO + H O\n2\n*CO + H+ + e⁻ → *CHO\n*CHO + *CO → *CHOCO\n*CHOCO + H+ + e⁻ → *CH OCO\n2\n*CH OCO + H+ + e⁻ → *CH OHCO\n2 2\n*CH OHCO + H+ + e⁻ → *CH OHCOH\n2 2\n*CH OHCOH + H+ + e⁻ → *CH OHC + H O\n2 2 2\n*CH OHC + H+ + e⁻ → *CH C + H O\n2 2 2\n*CH C + H+ + e⁻ → *CH CH\n2 2\n*CH CH + H+ + e⁻ → *CH CH\n2 2 2\n*CH CH → C H ↑ + *\n2 2 2 4\nThe pathway 2 for CO reduction to C H involves:\n2 2 4\nCO + * → *CO\n2 2\n*CO + H+ + e⁻ → *COOH\n2\n*COOH + H+ + e⁻ → *CO + H O\n2\n*CO + H+ + e⁻ → *CHO\n*CHO + *CO → *CHOCO\n*CHOCO + H+ + e⁻ → *CH OCO\n2\n*CH OCO + H+ + e⁻ → *CH OCOH\n2 2\n*CH OCOH + H+ + e⁻ → *CH OCHOH\n2 2\n*CH OCHOH + H+ + e⁻ → *CH OCH + H O\n2 2 2\n*CH OCH + H+ + e⁻ → *CH OHCH\n2 2\n*CH OHCH + H+ + e⁻ → *CH CH + H O\n2 2 2\n*CH CH + H+ + e⁻ → *CH CH\n2 2 2\n*CH CH → C H ↑ + *\n2 2 2 4\nSupplementary Fig. 51 | Proposed reaction pathway for CO reduction to C H .\n2 2 4\n…This strict temporal coupling between the formation of C–C coupling intermediates\nand interfacial reconstruction demonstrates that the O -mediated dynamic interfacial\n2\nrestructuring effectively reduces the energy barrier for C–C coupling, thereby\nenabling precise regulation of the C H synthesis pathway. Furthermore, the\n2 4\nRu Cu /CeO catalyst surface showed characteristic vibrational modes for surface-\n0.6 1 2\nbound *OH radicals (3568, 3627, and 3648 cm⁻1) and dissociative H O adsorption via\n2\nʋ(O–H) stretches (3670, 3701, and 3734 cm⁻1; Supplementary Fig. 49). These\nsignatures confirm hole-mediated H O dissociation pathway that supplies protons for\n2\n“3. Following up the previous question, are oxygen evolution and CO reduction\n2\ncompeting for the same active site in the process? Besides, once the O is formed, will\n2\nbe reduce via the Oxygen Reduction Reaction? If this is the case, this will further\ncompete with CO reduction, being another electron sink.”\nadsorption and oriented activation of reactant molecules within catalyst\nmicroenvironments critically govern product selectivity. CO temperature-\n2\nprogrammed desorption (CO -TPD) analysis (Fig. 4a) revealed that Ru /CeO\n2 0.6 2\nexhibited a weak peak at ~250 °C, indicating weak CO adsorption/activation on Ru\n2\nsites. In contrast, Ru Cu /CeO and Ru Cu (Cu0–Cu1+)/CeO showed significantly\n0.6 1 2 0.6 1 2\nenhanced desorption peaks between 400–500 °C. These peaks arise from CO\n2\nadsorption and activation at bimetallic alloy sites, thereby promoting deep CO\n2\nreduction. H O-TPD analysis (Fig. 4b) demonstrated a dissociation peak at 250–\n2\n350 °C for Ru /CeO , attributed to water dissociation at coordinatively unsaturated\n0.6 2\nRu sites. Ru Cu /CeO and Ru Cu (Cu0–Cu1+)/CeO exhibited prominent\n0.6 1 2 0.6 1 2\ndissociation peaks at 328 °C and 340 °C, respectively, where atomically dispersed Ru\nsites facilitate efficient water oxidation for O release.\n2 4\nintermediates. a, CO -TPD. b, H O-TPD.\n2 2\nFurthermore, mechanistic analysis of the four-electron oxygen evolution reaction\nrevealed that kinetics proceed via sequential proton-coupled electron transfer steps\nalong the *OH → *O → *OOH pathway (Supplementary Fig. 14). Systematic DFT\ncalculations of intermediate adsorption free energies (*OH, *O, *OOH) showed that\nRu single-atom catalysts and Ru Cu clusters exhibited theoretical limiting potentials\n0.6 1\nof 1.83 eV and 3.38 eV, respectively, during the potential-determining *OOH\nformation step. Atomically dispersed Ru sites optimally balance intermediate\nadsorption/desorption, overcoming kinetic limitations in alloyed catalysts during\n*OOH generation. Consequently, isolated Ru sites are identified as the active OER\nsites governing H O oxidation.\nRu\n0.6\nCu\n1\ncluster catalyst in each elementary step of oxygen evolution reaction.\nSupplementary Discussion: Mechanistic analysis of the four-electron oxygen\nevolution reaction revealed that the reaction kinetics proceeded via sequential proton-\ncoupled electron transfer steps along the *OH → *O → *OOH intermediate pathway.\nSystematic density functional theory calculations of the adsorption free energies for\nthese intermediates (*OH, *O, and *OOH) demonstrated that Ru single-atom catalysts\nand Ru Cu cluster catalysts exhibited theoretical limiting potentials of 1.83 eV and\n0.6 1\n3.38 eV, respectively, during the potential-determining step associated with terminal\n*OOH intermediate formation. Atomically dispersed Ru sites achieved an optimal\nbalance between intermediate adsorption and desorption processes. This dynamic\nequilibrium effectively circumvented the kinetic limitations observed in alloy\ncatalysts during the *OOH formation stage. Consequently, the isolated Ru centers\nwere identified as the catalytically active sites responsible for governing the H O\n2\noxidation process.\nTo rigorously verify whether oxygen undergoes further reduction during the\nCO RR, we performed catalytic experiments under concentrated solar irradiation. A\n2\ncirculating water-cooling system maintained a constant temperature at the reactor’s\ninner wall, effectively suppressing potential thermal decomposition of hydrogen\nperoxide (H O ; 2H O → O + 2H O). Post-reaction, we injected 30 mL high-purity\n2 2 2 2 2 2\ndeionized water (18.2 MΩ·cm) quantitatively through a septum. The system was\nvortex-mixed (200 rpm, 3 min) to desorb species and enable quantitative transfer of\nwall-adsorbed products into the aqueous phase (Supplementary Fig 27a). Critically,\npost-extraction analysis detected no quantifiable H O (Supplementary Fig 27b),\n2 2\nindicating that detectable O reduction to H O did not occur under these conditions.\n2 2 2\nThis result aligns with the inherent limitations of direct H O synthesis in gas-phase\n2 2\nsystems (Energy Environ. Sci., 2024, 18, 6482–6498; Chem. Soc. Rev., 2020, 49,\n6605–6631; Adv. Mater., 2024, 36, 2412386). The revised manuscript and\nSupplementary Information now include additional content, which is distinguished by\na yellow background.\nSupplementary Fig. 27 | a Operational schematic of a photoreactor assembly for\nphotothermal catalytic H O production. b Yield diagram for different catalysts under\n2 2\nconcentrated solar irradiation.\n…This C → C transition aligns with the Langmuir–Hinshelwood surface reaction,\n1 2\nindicating that there is dynamic competition between the C H formation pathways\n2 4\nand consumption of CO intermediates. To rigorously verify if oxygen is further\nreduced during CO reduction, we performed catalytic experiments under\n2\nconcentrated solar irradiation. Post-extraction analysis detected no quantifiable H O\n2 2\n(Supplementary Fig. 27). Mass spectrometry-calibrated and baseline-corrected gas\nchromatography data validated the concurrent enhancement of C H selectivity with\n2 4\nCO conversion (Supplementary Figs. 28 and 29)…\nPhotocatalytic H O production\n2 2\nAfter photo-thermal catalytic CO reduction, 30 mL high-purity deionized water (18.2\ncirculator (5.0 ± 0.1°C) minimized thermal degradation of H O . Components\n2 2\nadhering to reactor walls were fully dissolved in the aqueous phase by vortex mixing\n(200 rpm, 3 min), ensuring quantitative product recovery. H O concentration was\n2 2\nthen quantified via standardized iodometric titration.\nMeasurement of H O concentration\n2 2\nH O concentration was determined using a standardized iodometric method39. Briefly,\n2 2\n1 mL 0.1 M potassium hydrogen phthalate (C\n4\n) aqueous solution was added to\nthe sample, followed by 1 mL of 0.4 M potassium iodide (KI) aqueous solution. After\na 30 min reaction period, H O reacted with iodide anions (I−) under acidic conditions\n2 2\naccording to the reaction: H O + 3I− + 2H+ → I − + 2H O, producing triiodide anions\n2 2 3 2\n(I −) that exhibit strong absorption at 350 nm. I − concentration was quantified using\n3 3\nUV-Vis spectroscopy, allowing calculation of the H O concentration generated.\n2 2\nReferences\nsustainable photocatalytic H O generation. Angew. Chem. Int. Ed. e202508718\n2 2\n(2025).\n“4. Besides these general questions, how are the formation energies in Fig. 1f\ncalculated? Which reference energies (bulk metal or?) and equations were used?”\nWe sincerely grateful for this valuable comment. The formation energy (ΔE) for the\nf\nCu Ru binary metal cluster (x + y = 16) in Fig. 1f was defined as: ΔE (x, y) = E\nx y f total\n(Cu Ru ) − E (Cu ) − E (Ru ). E (Cu Ru ), E (Cu ) and E (Ru )\nx y total x total y total x y total x total y total x y\nrepresent the total energies for the ground states of the Cu Ru , Cu and Ru clusters,\nx y x y\nrespectively. ΔE < 0 indicates that the formation of Cu Ru cluster from separated\nf x y\nCu and Ru is an exothermic process, and the larger the negative value, the more\nx y\nstable it is. We have now added the definition in the method section of our revised\nmanuscript.\nDFT-based computational framework for surface adsorption energetics and\nreaction thermodynamics\nAll first principles calculations were carried out within the framework of DFT as\nimplemented in Vienna ab initio simulation package (VASP)44,45. Periodic boundary\nconditions were applied to simulate the surfaces of the two-dimensional slabs, with a\nvacuum spacing of 20 Å. The reciprocal space was sampled by a fine grid of 3 × 3 × 1\nk-points in the Brillouin zone46. We used projector-augmented-wave (PAW)\npseudopotentials and the Perdew-Burke-Ernzerhof (PBE) exchange-correlation\napproximation47-49. Electronic wave function was expanded on a plane wave basis set\nwith the cutoff energy of 500 eV. A total energy difference between subsequent self-\nconsistency iterations below 10−5 eV was used as the criterion for reaching self-\nconsistency. All geometries were optimized using the conjugate-gradient method50,\nuntil none of the residual Hellmann-Feynman forces exceeded 10−2 eV/Å.\nGibbs free energy change (𝐺) of each chemical reaction step was calculated by:\n𝐺 = 𝐸 +𝐸 −𝑇𝑆 (10)\n𝐷𝐹𝑇 𝑍𝑃𝐸\nwhere 𝐸 , 𝐸 , 𝑇, and 𝑆 denote total energy obtained from DFT, zero-point energy,\n𝐷𝐹𝑇 𝑍𝑃𝐸\ntemperature, and entropy, respectively. The temperature was set as room temperature,\ni.e. 298.15 K. The zero-point energy and entropy were calculated in VASPKIT code49.\nAdsorption energy ∆𝐸 on the surface of substrates was defined as:\n𝑎𝑑\n∆𝐸 = 𝐸 −(𝐸 +𝐸 ) (11)\n𝑎𝑑 ∗𝑚𝑜𝑙𝑒 ∗ 𝑚𝑜𝑙𝑒\nwhere 𝐸 , 𝐸 , and 𝐸 denote energies of the adsorbed molecule on substrates,\n∗𝑚𝑜𝑙𝑒 ∗ 𝑚𝑜𝑙𝑒\nthe bare substrates, and the molecule.\nThe formation energy (ΔE) for the Cu Ru binary metal cluster (x + y = 16) in Fig. 1f\nf x y\nwas defined as: ΔE (x, y) = E (Cu Ru ) − E (Cu ) − E (Ru ). E (Cu Ru ),\nf total x y total x total y total x y\nE (Cu ) and E (Ru ) represented the total energies for the ground states of the\ntotal x total y\nCu Ru , Cu and Ru clusters, respectively. ΔE < 0 indicated that the formation of\nx y x y f\nCu Ru cluster from separated Cu and Ru was an exothermic process, and the larger\nx y x y\nthe negative value, the more stable it was.\n“5. If I undertand correctly molecular dynamics were carried out on a\nwater/CO /catalyst interface to demonstrate water aggregation on clean CeO (see\n2 2\nFig. S28). I wonder whether these simulations are actually meaningful, as water\nchanges from liquid to gas moving beyond 100 degrees celsius.”\nWe sincerely appreciate the efforts made by the Reviewer in carefully reviewing our\nmanuscript and providing valuable feedback. Regarding simulation validity: This\nstudy employed molecular dynamics simulations to elucidate surface diffusion\nbehavior of reactant molecules under high-temperature (Supplementary Fig. 45). The\nsimulations revealed a marked increase in gaseous species diffusion coefficients with\nrising temperature, driven by thermally activated molecular collisions and kinetic\nenergy transfer. Notably, while weak adsorption aggregation (physisorption) occurs at\ncatalytic active sites, the catalytic process was dominated by chemisorption—a\nconclusion corroborated by temperature-programmed desorption (TPD) profiles of\nvarious gases (Fig. 4a–d). Phase-state validity was addressed through NVT ensemble\nsimulations. The initial system was constructed based on condensed-phase fluid\ndensity benchmarks (ρ = 1.681 g/cm3). Per the ideal gas law (PV = nRT), pressure\nscaled proportionally with temperature at constant volume, maintaining the H O/CO\n2 2\nmixture in a dense fluid state under supercritical conditions. Furthermore, finite-size\neffects intrinsic to molecular dynamics were rigorously evaluated: even minimal test\nsystems (single water molecules) exhibited water densities of 2.069 × 106 g/m3 under\nperiodic boundary conditions—several orders of magnitude higher than actual vapor-\nphase conditions (2.99 × 102 g/m3). To verify universality, supplementary simulations\nof low-molecular-weight systems consistently reproduced the weak adsorption\naggregation of reactant molecules (Supplementary Fig. 46). Consequently, the\nexpanded model system ensured significant observability of this phenomenon, with its\nphysical mechanism validated through multiscale modeling. The revised manuscript\nand Supplementary Information now include additional content, which is\ndistinguished by a yellow background.\nSupplementary Fig. 45 | a-c Mean squared displacement profiles of H O (a), O (b),\n2 2\nand CO (c) on Ru Cu /CeO from molecular dynamics simulations at discrete\n2 0.6 1 2\ntemperatures (25, 150, 300, 450, 600 °C), demonstrating temperature-dependent\ndiffusion behaviors.\nFig. 4 | Active sites verification and operando characterization of C H -formation\n2 4\nintermediates. a, CO -TPD. b, H O-TPD. c, O -TPD. d, CO-TPD.\n2 2 2\nSupplementary Fig. 46 | Low-molecular-weight systems molecular dynamics\nsimulations.\nSupplementary Discussion: Finite-size effects intrinsic to molecular dynamics were\nrigorously evaluated: even minimal test systems (single water molecules) exhibited\nwater densities of 2.069 × 106 g/m3 under periodic boundary conditions—orders of\nmagnitude higher than actual vapor-phase conditions (2.99 × 102 g/m3). To verify\nuniversality, supplementary simulations of low-molecular-weight systems consistently\nreproduced the weak adsorption aggregation of reactant molecules. Consequently, the\nexpanded model system ensures significant observability of this phenomenon, with its\nphysical mechanism validated through multiscale modeling.\nDuring photothermal catalysis, the dynamic adsorption and oriented activation of\nreactant molecules are key to achieving product selectivity. Molecular dynamics\nsimulations revealed that the Ru/Cu alloy clusters in the Ru Cu /CeO system induce\n0.6 1 2\nthe formation of dynamic solvation layers between CO and O (Supplementary Fig.\n2 2\n44), whereas the Ru single-atom sites exhibit a specific adsorption enrichment toward\nH O. This spatially selective physical adsorption is enhanced at elevated temperatures\n2\nbecause of the increased collision frequency between the molecules and active sites\n(Supplementary Fig. 45). Supplementary simulations of low-molecular-weight\nsystems consistently reproduced the weak adsorption aggregation of reactant\nmolecules (Supplementary Fig. 46). Consequently, the expanded model system\nensures significant observability of this phenomenon.\nReviewer #2:\n“1. This work reports a Ru Cu (Cu0-Cu+)/CeO catalyst constructed through an O -\n0.6 1 2 2\nmediated dynamic interface reconstruction strategy for photothermal catalytic CO\n2\nreduction to ethylene (C H ). The study utilizes single-atom Ru doping to induce a\n2 4\ndistorted pentahedral coordination field that accelerates H O dissociation, and\n2\ntriggers O -driven self-assembly of Cu0–Cu+ gradient interfaces through the\n2\nphotothermal effect, optimizing *CHOCO adsorption and C–C coupling pathways,\nthereby addressing catalyst poisoning under high oxygen partial pressure and\nsluggish C–C coupling kinetics. However, the characterization of single-atom active\nsites, potential changes in catalyst elemental valence states, and the modulation\nmechanism of valence states by O require further refinement. Additionally, the\n2\nwriting of the manuscript needs to be clearer and more fluent. Specific comments are\nas follows:”\nWe sincerely appreciate the Reviewer’s positive assessment of our work and their\ninsightful suggestions. In response to the specific comments regarding the\ncharacterization of single-atom active sites, potential valence state evolution of\ncatalyst elements, mechanistic understanding of O -mediated valence modulation, and\n2\nmanuscript clarity, we implemented comprehensive revisions: (1) Deeper analysis of\nexisting high-resolution synchrotron-based XAFS and atomic-resolution AC-\nHAADF-STEM characterization was performed to rigorously resolve the Ru single-\natom structure. (2) Quasi-in situ XPS and Quasi-in situ XANES studies were\nconducted to systematically track dynamic Cu0/Cu1+ valence transitions during\nphotothermal reactions. (3) Combined DFT calculations and Operando DRIFTS\nanalysis elucidated O ’s critical role in driving interface reconstruction and stabilizing\n2\nthe Cu0–Cu1+ valence gradient for enhanced *CHOCO adsorption. (4) The manuscript\nunderwent comprehensive linguistic refinement and structural reorganization to\nimprove logical flow, technical precision, and readability. We have diligently\naddressed each of these comments in a point-by-point manner and have incorporated\nadditional contents into the revised manuscript and corresponding Supplementary\nInformation.\n“2. The background introduction in the Introduction section is insufficient. Compared\nto the current approach of integrating conclusions from previous related work, the\nauthors need a more complete and independent logical chain to highlight the\ninnovation and starting point of this work.”\nWe sincerely appreciate this valuable comment. In response, we systematically\nrestructured the “Introduction” section to strengthen the contextual overview of\nexisting research and critical bottleneck analyses. This foundation clarifies our study’s\ndistinctive entry point and innovative motivation. Additionally, we developed a logic\ndiagram (Fig. R1) to visually outline the complete causal chain—from research\nchallenges through theoretical breakthroughs to our proposed solution—precisely\narticulating this work’s original contributions and research origins. These results have\nbeen incorporated into the revised manuscript and are also attached below, with new\ncontent highlighted in yellow.\nFigure R1 | General framework of Introduction section.\nIntroduction\nA central constraint impeding the practical implementation of artificial photosynthesis\nis the efficient conversion of carbon sources under oxygen-rich environments—\nencountered in industrial flue gas or ambient air1,2. This fundamental challenge arises\nfrom cascade attenuation in solar-to-chemical energy conversion. Prevailing strategies\nfor improving energy efficiency employ concentrated light systems to generate\ntransient high-temperature microenvironments and elevated photon-flux densities on\ncatalyst surfaces3,4. However, this approach accelerates water dissociation, triggering\nexplosive proliferation of the O byproduct (with molar yields reaching 3–5 times\n2\nthose of the primary CO reduction products). Consequently, it induces an exponential\n2\nrise in system oxygen partial pressure, establishing a self-reinforcing negative\nfeedback loop where “intensified light input ↔ microenvironment deterioration”\nmutually amplifies. This loop comprehensively suppresses catalytic activity through\ndual thermodynamic and kinetic inhibition: (1) Thermally, the oxygen reduction\nreaction (ORR) competes with the target CO reduction reaction (CO RR) for electron\n2 2\ntransfer pathways5; (2) Kinetically, persistent accumulation and monolayer coverage\nof oxygen adsorption states on catalyst surfaces obstruct CO chemisorption and\n2\nactivation pathways. Ultimately, conversion efficiency decreases by 2–3 orders of\nmagnitude relative to anaerobic systems6. Current oxygen-tolerance strategies\n(physical isolation/surface passivation) have remained fundamentally limited by the\n“oxygen-as-poison” paradigm and competitive adsorption framework7. These\napproaches passively suppress ORR but fail to mitigate system-level perturbations\ninduced by drastic oxygen partial pressure fluctuations, creating inherent\nincompatibility with real-world oxidative environments. Consequently, designing\nintrinsically oxygen-tolerant gas-solid catalytic interfaces is imperative. Such systems\nmust efficiently mitigate O poisoning while productively leveraging oxygen\n2\nmolecules as “triggers” to induce steady-state self-assembly of active sites. This\nwould enable the directional construction of catalytic microenvironments adaptive to\nhigh-oxygen conditions, thereby decoupling efficient C=O bond activation from\ncompetitive CO /O adsorption kinetics—a prerequisite for practical deployment.\n2 2\nDuring hydrogenation-driven carbon-chain growth, single-atom catalysts (SACs)\nleverage their unique localized electronic structures and coordinative unsaturated to\nefficiently dissociate water molecules, continuously supplying active hydrogen\nspecies (*H) while optimizing proton-coupled electron transfer (PCET) kinetics8. Ru\nsingle atoms stabilized in the 0 < δ+ < 4 oxidation state (Ruδ+) precisely modulate the\nd-band center via their t orbital configuration. Synergistic interaction with the\n2g\nsupport’s strong electron effects establishes an electron-deficient microenvironment9,\nenhancing OER efficiency via three mechanisms: (1) Strengthening chemical\nadsorption of H O at active sites and lowering the O–H bond dissociation energy\n2\nbarrier; (2) Optimizing adsorption strength of key oxygen intermediates (*OH, *O, and\n*OOH), circumventing conventional Sabatier principal limitations; (3) Significantly\nreducing kinetic overpotential in PCET steps. However, spatial confinement at single\natomic sites induces competitive adsorption, thermodynamically stabilizing the linear\nadsorption configuration of *CO intermediates during CO activation. This results in\n2\nsymmetry mismatch between the C atom’s p orbital and the metal atom’s dz² orbital,\nx\nseverely inhibiting the sp3 hybridization transition required for C–C coupling. To\novercome this limitation, a multi-active-site system integrating single atoms with\nalloy clusters is essential. The core strategy involves concerted modulation of discrete\nd-band orbitals and interfacial charge distribution to drive the dynamic transition of\n*CO from linear to bridging adsorption, thereby facilitating carbon chain growth10.\nUnder aerobic conditions, Cu-based polymetallic interfaces exhibit dual advantages in\nterms of O activation and directional carbon chain construction. The Cu sites\n2\ndynamically coordinate to form M–O–Cu antioxidation networks, which selectively\ndestruct reactive oxygen species and enable the catalytic microenvironment to self-\nrepair, thereby avoiding catalyst deactivation under oxidative conditions11.\nSimultaneously, Cu0–Cu1+ charge-gradient interfaces are generated in situ, which\ninduce the reconstruction of *CHOCO adsorption sites through electron redistribution\nand break the spatial symmetry of linear adsorption configurations. This balances the\ncoverage of intermediates with their reaction kinetics, resulting in a significant\nenhancement in selectivity for hydrocarbon products12…\nReferences\n2\nphotocatalysts with oxygen. Chem 5, 1818−1833 (2019).\n2\nmicroporous Pd-porphyrin-based polymers coated hollow TiO . Nat. Commun.\n2\n13, 1400 (2022).\n2 2\nconversion efficiency. Nat. Commun. 15, 4675 (2024).\nframeworks for solar energy conversion: past, present and future. Angew. Chem.\nInt. Ed. 63, e202413096 (2024).\nconsequences during CH –O catalysis on supported Pt clusters. J. Am. Chem.\n4 2\nSoc. 133, 15958−15978 (2011).\n2\nframeworks via photoswitching control oxygen passivation strategy. Nat.\nCommun. 15, 1479 (2024).\nnanoarchitecture with N O coordinated Ni single-atom catalysts for hydrogen\n2 2\nevolution. J. Am. Chem. Soc. 147, 16522−16535 (2025).\nCo catalyst with dual atomically dispersed active centers. Chem. Sci. 12,\n7125−7137 (2021).\n“3. The description of Fig.1a-1e in the Discussion section reads more like content for\nthe Introduction. Furthermore, the rationale for choosing a Ru single-atom catalyst\nneeds to be explained.”\nWe sincerely thank the Reviewer for the professional comments, which prompted\ndeeper reflection and refinement of the scientific rationale. Regarding the selection of\nRu single-atom catalysts, the core scientific basis was as follows: (1) Ru’s unique\nelectronic structure allowed for superior modulation of adsorption energies for\nreaction intermediates. This structural characteristic closely aligned with the reaction\nmechanism elucidated in this study, enabling efficient activation of key molecules and\nreducing of the energy barrier in the rate-determining step. (2) The strong metal-\nsupport interaction between Ru single atoms and the support not only stabilized\natomically dispersed active sites but also optimized the electronic state via specific\ncoordination environments. This synergy constituted a key advantage over Ru\nnanoparticles or other metal single-atom catalysts. These results have been\nincorporated into the revised manuscript and are also attached below, with new\ncontent highlighted in yellow.\n…During hydrogenation-driven carbon-chain growth, single-atom catalysts (SACs)\nleverage their unique localized electronic structures and coordinative unsaturated to\nefficiently dissociate water molecules, continuously supplying active hydrogen\nspecies (*H) while optimizing proton-coupled electron transfer (PCET) kinetics8. Ru\nsingle atoms stabilized in the 0 < δ+ < 4 oxidation state (Ruδ+) precisely modulate the\nd-band center via their t orbital configuration. Synergistic interaction with the\n2g\nsupport’s strong electron effects establishes an electron-deficient microenvironment9,\nenhancing OER efficiency via three mechanisms: (1) Strengthening chemical\nadsorption of H O at active sites and lowering the O–H bond dissociation energy\n2\nbarrier; (2) Optimizing adsorption strength of key oxygen intermediates (*OH, *O, and\n*OOH), circumventing conventional Sabatier principal limitations; (3) Significantly\nreducing kinetic overpotential in PCET steps. However, spatial confinement at single\natomic sites induces competitive adsorption, thermodynamically stabilizing the linear\nadsorption configuration of *CO intermediates during CO activation. This results in\n2\nsymmetry mismatch between the C atom’s p orbital and the metal atom’s dz² orbital,\nx\nseverely inhibiting the sp3 hybridization transition required for C–C coupling. To\novercome this limitation, a multi-active-site system integrating single atoms with\nalloy clusters is essential. The core strategy involves concerted modulation of discrete\nd-band orbitals and interfacial charge distribution to drive the dynamic transition of\n*CO from linear to bridging adsorption, thereby facilitating carbon chain growth10…\nReferences\nnanoarchitecture with N O coordinated Ni single-atom catalysts for hydrogen\n2 2\nevolution. J. Am. Chem. Soc. 147, 16522−16535 (2025).\nCo catalyst with dual atomically dispersed active centers. Chem. Sci. 12,\n7125−7137 (2021).\n“4. What do Ru Cu /CeO and Ru /CeO represent? Please specify upon their first\n0.6 1 2 0.6 2\nmention. The coordinate state of the single-atom catalysts should be clarified in more\ndetail, for example, with experimental verification of the Ru:Cu 3:5 stoichiometric\nratio.”\nWe sincerely thank the Reviewer for this professional comment. The structural\nconfigurations of the Ru /CeO and Ru Cu /CeO catalysts were explicitly\n0.6 2 0.6 1 2\ndescribed upon their initial introduction in the manuscript, with further emphasis on\nthe local coordination environment of Ru single atoms through near-edge structure of\nRu K edge X-ray absorption and Fourier transform extended X-ray absorption fine\nstructure characterization. The Ru:Cu stoichiometric ratio (≈ 3:5) was precisely\nverified by inductively coupled plasma mass spectrometry (ICP-MS) (Supplementary\nTable 3). This analysis confirmed close agreement between the experimentally\nmeasured Ru/Cu atomic ratio and the theoretical value calculated from precursor\namounts, demonstrating the accuracy of the catalyst composition. These results have\nbeen incorporated into the revised manuscript and are also attached below, with new\ncontent highlighted in yellow.\nSupplementary Table 3 | Ru and Cu loadings in CeO -supported catalysts.\nSample content contenta content contenta\n(wt%) (wt%) (wt%) (wt%)\nRu /CeO 0.6 0.58 0 0\n0.6 2\nCu /CeO 0 0 1 0.97\n1 2\nRu Cu /CeO 0.2 0.23 0.6 0.58\n0.2 0.6 2\nRu Cu /CeO 0.6 0.57 1 1.02\n0.6 1 2\nRu Cu /CeO 0.5 0.53 0.5 0.48\n0.5 0.5 2\nRu Cu /CeO 1 0.96 0.6 0.57\n1 0.6 2\nRu Cu /CeO 0.6 0.62 0.2 0.22\n0.6 0.2 2\na The Ru and Cu loadings were quantified by inductively coupled plasma-mass\nspectrometry (ICP-MS).\n…To analyze the distribution patterns of metallic Ru and Cu on the CeO support,\n2\nthree-dimensional conformational characterization of Ru Cu /CeO (Co-existence of\n0.6 1 2\nmonatomic Ru and Ru/Cu alloy) was conducted using atomic-resolution HAADF-\nSTEM…\n…First, the catalytic activity of bare CeO and single-atom catalysts (Ru /CeO and\n2 0.6 2\nCu /CeO ) was evaluated for the co-reduction of CO and H O under non-\n1 2 2 2\nconcentrated solar irradiation (Fig. 3a)…\n…Three coordination structures were identified: short-range Ru–Cu metallic bonding\n(coordination number [CN] = 0.6 ± 0.2 at R = 2.53 Å), second-nearest-neighbor Ru–\nRu coordination (CN = 1.6 ± 0.1 at R = 2.68 Å), and long-range Ru–O interactions\n(CN = 5.9 ± 0.2 at R = 2.01 Å) (Supplementary Table 1). The Ru–O coordination\nnumber and bond length provided strong evidence that a portion of Ru species existed\nas atomically dispersed single atoms. This CN value closely matched the theoretical\ncoordination number (~6) for Ru in octahedral sites within the fluorite structure of\nCeO . Combined with the observed Ru–O bond distance, these results demonstrated\n2\nthat a significant population of Ru atoms occupied CeO lattice sites, forming stable,\n2\nhigh-coordination bonds with oxygen atoms and thereby anchoring as single-atom\nspecies (Ru–O–Ce). This high-coordination environment was distinct from surface-\nadsorbed oxygen species, which typically exhibited lower coordination numbers (CN\n< 2). This discovery of a multiscale coordination architecture reveals that Ru atoms\nprimarily exist as isolated single atoms in the Ru Cu /CeO catalyst, with others\n0.6 1 2\nforming sub-nanoclusters with Cu.…\n“5. The calculations in Fig. 1 only demonstrate that Ru Cu is the most readily\n3 5\nformed stable structure; this cannot be directly used as the reason for influencing the\ncatalyst's product selectivity.”\nWe sincerely thank the Reviewer for the meticulous examination of our manuscript.\nWe apologize for the potentially misleading statement regarding the structure-\nselectivity relationship. We fully acknowledged that the data in Fig. 1f demonstrated\nonly the thermodynamic stability and kinetic accessibility of the Ru Cu cluster. We\n3 5\nagreed that this finding alone could not rationalize product selectivity. Consequently,\nwe have revised the manuscript to remove any description of a direct structure-\nselectivity correlation derived from this figure. These results have been incorporated\ninto the revised manuscript and are also attached below, with new content highlighted\nin yellow.\n…Theoretical screening (Fig. 1f) identifies the Ru Cu cluster as the\n3 5\nthermodynamically most stable and kinetically most accessible structure within the\nRu Cu /CeO system, providing a foundational framework for potential active site\nx y 2\nconfigurations in practical catalysts. Guided by this prediction, bimetallic\n(Ru Cu /CeO ; x = 0.2–1, y = 1–0.2) catalysts with both Ru single-atom sites and sub-\nx y 2\nnanoscale alloy clusters were prepared (Supplementary Table 3). The Ru Cu /CeO\n0.6 1 2\ncatalyst, developed through precise composition control, demonstrated exceptional\ncatalytic performance, with CO, CH , and O production rates of 40.5, 7.8, and 50.8\n4 2\nmol·g−1·h−1, respectively (Fig. 3a). This significantly outperformed catalysts with\nother Ru/Cu ratios. The close stoichiometric match (Ru:Cu ≈ 3:5) to the theoretically\npredicted optimal Ru Cu structure validates the computational guidance for\n3 5\nsynthesizing materials with high-activity architectures…\n“6. The performance analysis in lines 278-280 and 296-307 does not specify which\nfigure/chart it refers to.”\nWe sincerely thank the Reviewer for meticulous examination of our manuscript. The\nsentence has been revised based as also shown below:\n…Theoretical screening (Fig. 1f) identifies the Ru Cu cluster as the\n3 5\nthermodynamically most stable and kinetically most accessible structure within the\nRu Cu /CeO system, providing a foundational framework for potential active site\nx y 2\nconfigurations in practical catalysts. Guided by this prediction, bimetallic\n(Ru Cu /CeO ; x = 0.2–1, y = 1–0.2) catalysts with both Ru single-atom sites and sub-\nx y 2\nnanoscale alloy clusters were prepared (Supplementary Table 3). The Ru Cu /CeO\n0.6 1 2\ncatalyst, developed through precise composition control, demonstrated exceptional\ncatalytic performance, with CO, CH , and O production rates of 40.5, 7.8, and 50.8\n4 2\nmol·g−1·h−1, respectively (Fig. 3a). This significantly outperformed catalysts with\nother Ru/Cu ratios. The close stoichiometric match (Ru:Cu ≈ 3:5) to the theoretically\npredicted optimal Ru Cu structure validates the computational guidance for\n3 5\nsynthesizing materials with high-activity architectures…\n…Time-resolved kinetic analysis revealed the temporal trend of product evolution\n(Fig. 3c). During the initial reaction phase (0–30 min), CO accumulated rapidly,\nreaching a peak concentration of 794 ± 45 mol·g−1 at 30 min. Some C H evolution\n2 4\n(62.6 ± 8 mol·g−1) and substantial O generation (640 ± 25 mol·g−1) were also\n2\nobserved; therefore, we hypothesized that O , which is produced as a byproduct of the\n2\nclusters through oxidative etching…\n“7. Lines 300-304: More material characterization is needed, rather than speculating\nabout possible valence changes in Cu based solely on performance variations.”\nWe sincerely thank the Reviewer for the very important comments and suggestion. In\nresponse to the request for direct material characterization beyond performance-based\ninferences about Cu valence states, we conducted supplementary experiments tracking\nCu oxidation state evolution. Quasi in-situ XPS analysis of Cu LMM Auger spectra\n(Fig. 3f) revealed only the metallic Cu0 peak (918.6–919.4 eV) during the initial\nreaction phase (0–15 min), with a distinct Cu1+ peak emerging at 913.4–913.9 eV after\n30 min; the relative Cu1+ concentration progressively increased with irradiation time,\nreaching 58% at 120 min. Given that concentrated solar irradiation precluded\nsynchrotron-based in situ characterization, Quasi in-situ XANES analysis showed the\nCu K-edge aligned with Cu0 foil at 0 min, shifted to higher energies by 30 min\n(indicating Cu+ formation), intensified at 60 min, and stabilized between Cu0 and\nCu1+ standards at 120 min, confirming a mixed Cu0/Cu1+ state (Supplementary Fig.\n37). These complementary results consistently demonstrated dynamic oxidation state\nevolution from Cu0 to Cu0/Cu1+, kinetically correlating with prior O gradient\n2\nexperiments to confirm molecular oxygen drove in situ formation of the Cu0–Cu1+\ninterface. This interface modulated active-site electronic structure, optimized\nadsorption energetics for C–C coupling intermediates and governed catalytic behavior.\nThese results have been incorporated into the revised manuscript and are also attached\nbelow, with new content highlighted in yellow.\nFig. 3 | O -mediated photothermal catalytic CO reduction performance. f,\n2 2\nQuasi-in situ Cu L3VV Auger XPS spectra for Ru Cu /CeO catalyst.\n0.6 1 2\nSupplementary Fig. 37 | Quasi in situ XANES spectra at Cu K-edge of Cu foil, CuO,\nCu O, Ru Cu /CeO and Ru Cu (Cu0–Cu1+)/CeO .\n2 0.6 1 2 0.6 1 2\n…During the initial reaction phase under concentrated solar irradiation (0–15 min),\nthe Cu LMM Auger spectra exhibited only the characteristic peaks of metallic Cu\n(Cu0; 918.6–919.4 eV). At 30 min, Cu1+ species emerged (913.4–913.9 eV), and their\nrelative abundance progressively increased to 58% as the reaction proceeded further\n(Fig. 3f)23. No Cu2+ species were detected in the higher binding energy range during\nthe quasi in situ XPS analysis (Supplementary Fig. 36). Quasi in situ XANES analysis\nrevealed that the Cu K-edge spectrum matched that of the Cu foil reference at 0 min.\nThe edge shifted to higher energies after 30 min of exposure, indicating oxidation to\nCu+. This shift intensified by 60 min and stabilized at a position intermediate\nbetween the Cu0 and Cu1+ reference spectra by 120 min (Supplementary Fig. 37),\nindicating a mixed Cu0/Cu1+ oxidation state. This valence evolution correlates well\nwith the results of the O concentration gradient experiments; O acts as an oxidant,\n2 2\nmediating the in situ formation of dynamic Cu0–Cu1+ interfaces, thereby optimizing\nthe adsorption of C–C coupling intermediates.\n“8. Lines 410-418: What does \"replacing CO /H O with equimolar CO\" mean? Does\n2 2\nit mean replacing CO ? If not, where would the hydrogen source for C H come from?”\n2 2 4\nWe sincerely appreciate the efforts made by the Reviewer in carefully reviewing our\nmanuscript and providing valuable feedback. We are also very sorry for making\nmisleading. To clarify the experimental design: The term “replacing CO\n2\n/H\nequimolar CO” specifically denotes substituting CO\n2\nwith an equimolar amount of\nCO while maintaining a constant H\nfrom CO /H O to CO/H O, during which hydrogen species are exclusively sourced\n2 2 2\nfrom H O dissociation. All hydrogen species required for ethylene synthesis are solely\n2\nderived from H O. The sentence has been revised based as also shown below:\nreactant substitution strategy combined with diffuse reflectance infrared Fourier\ntransform spectroscopy (DRIFTS). Under constant H O dosage (1 mL), when the\n2\nreaction system was converted from CO /H O to CO/H O by substituting CO with an\n2 2 2 2\nequimolar amount of CO, the C H selectivity markedly increased from 74.3% to\n2 4\n89.7%, whereas an equimolar CH system completely suppressed C H production\n4 2 4\n(Supplementary Fig. 47). This demonstrates that CO undergoes reversible adsorption-\nactivation on the catalyst surface and serves as the key C intermediate for C–C bond\n1\nformation, whereas CH is excluded from the coupling network because of its lack of\n4\neffective adsorption and dissociation pathways.\n“9. The in-situ characterization does not clearly elucidate the role of O in the\nWe sincerely thank the Reviewer for the very important comment. To resolve\nambiguities in prior interpretations of the oxygen-mediated dynamic interface\nreconstruction mechanism, we supplemented our analysis with operando DRIFTS\ncharacterization of H O evolution and key oxygen-containing intermediates\n2\n(Supplementary Fig. 49). This time-resolved monitoring of the CO /H O co-\n2 2\nadsorption system under concentrated solar irradiation (AM 1.5G, 5000 mW cm−2)\ndirectly evidenced the underlying process：The characteristic peak at 3568–3648\ncm−1 confirmed the generation of surface-bound *OH radicals via photogenerated hole\noxidation (H O + * + h+ → *OH + H+). Concurrently, the ʋ(O–H) vibration at 3670–\n2\n3734 cm−1 indicated H O dissociation (Nat. Commun., 2024, 15, 4675; Nano energy,\n2\n2023, 113, 108578; Angew. Chem. Int. Ed., 2024, 63, e202410474). Under\nconcentrated solar irradiation, these *OH radicals efficiently underwent in situ\nbimolecular coupling (2*OH → H O + 1/2O ), yielding molecular oxygen at 910.5\n2 2\nμmol·g−1·h−1 (validated by gas chromatography, Supplementary Fig. 29). For the O -\n2\nmediated reconstruction mechanism, we proposed a three-step cascade: (1) O\n2\nadsorption and activation: O adsorbed on Cu0 and underwent single-electron transfer\n2\nto form superoxide radical (O + e− → ·O −); (2) O–O bond cleavage and\n2 2\noxidation: ·O − dissociated into atomic oxygen (·O − + h+ → 2*O), triggering charge-\n2 2\nconserved oxidation: 2Cu0 + *O → 2Cu+–O2−; (3) Dynamic interface formation: A\nCu0/Cu1+ heterointerface dynamically established. In situ XPS analysis after 30 min\nreaction captured a shifted Cu0/Cu1+ ratio (Fig. 3f). Combined with simultaneous\noperando DRIFTS detection of C–C coupling intermediates (Fig. 4e), this provided\nrigorous evidence for spatiotemporal coupling between O -driven interface\n2\nreconstruction and C product formation. This mechanism clarified the maintenance\n2\nof interfacial dynamic equilibrium (an O generation/consumption-driven redox cycle)\n2\nand fundamentally revealed the cascade under concentrated solar irradiation: water\ndissociating (generating *OH) → oxygen evolution (generating O ) → interfacial\n2\nreconstruction (forming Cu0/Cu1+) → C product formation.\n2\nevidenced by theoretical charge redistribution analysis. Bader charge analysis\nrevealed that the average charge of 10 Cu atoms decreased from 11.00 e− (consistent\nwith metallic copper electron density, Fig. 5a) before O adsorption to 10.71 e− (a loss\n2\nof 2.77 e−, Fig. 5b) after adsorption. Combined with charge gain at Ru sites (+0.81 e−)\nand electron capture by oxygen species (+1.95 e−), the results quantitatively satisfied\ncharge conservation: ΔQ\nCu\n(−2.77) ≈ ΔQ\nRu\n(+0.81) + ΔQ\nO\n(+1.95), confirming partial\noxidation of Cu0. Potential energy surface scanning (Supplementary Fig. 52) further\nrevealed that O adsorption was energetically most favorable (ΔE = −0.59 eV) at\n2 ads\nRu–Cu dual sites, triggering dynamic valence differentiation: Cu oxidized to +1\n7\nwhile Cu /Cu retained their metallic state (Fig. 5c). This oxygen-mediated atomic-\n8 10\nlevel redox heterogeneity established the active microenvironment for C–C coupling.\nThese results are involved in the revised manuscript and are also attached below.\nThese results have been incorporated into the revised manuscript and are also attached\nbelow, with new content highlighted in yellow.\nSupplementary Fig. 29 | Time-resolved raw gas-phase signals for O and H O\n2 2\nevolution during catalytic reaction (sampling intervals: 120 min).\nFig. 3 | O -mediated photothermal catalytic CO reduction performance. f,\n2 2\nQuasi-in situ Cu L3VV Auger XPS spectra for Ru Cu /CeO catalyst.\n0.6 1 2\nFig. 4 | Active sites verification and operando characterization of C H -formation\n2 4\nintermediates. e, Operando DRIFTS of CO /H O-derived C–C coupling\n2 2\nintermediates on Ru Cu /CeO .\n0.6 1 2\nFig. 5 | Theoretical calculation and CO reduction mechanism. a, b, Comparative\n2\nanalysis of side-view differential charge density for adsorption sites on bimetallic\nclusters under oxygen-deficient (a) and oxygen-rich conditions (b). The yellow and\nblue regions denote electron accumulation and depletion, respectively, with atomic\nconfigurations overlaid for spatial reference. c, Localized charge redistribution at ten\nsurface-projected high-symmetry Cu sites in Ru/Cu alloy clusters pre- and post-O\n2\nadsorption.\nSupplementary Fig. 52 | DFT-calculated O adsorption energies at distinct active\n2\nsites of the Ru Cu /CeO catalyst.\n0.6 1 2\nSupplementary Fig. 49 | Operando DRIFTS of H O activation intermediates on\n0.6 1 2\n…This strict temporal coupling between the formation of C–C coupling intermediates\nand interfacial reconstruction demonstrates that the O -mediated dynamic interfacial\n2\nrestructuring effectively reduces the energy barrier for C–C coupling, thereby\nenabling precise regulation of the C H synthesis pathway. Furthermore, the\n2 4\nRu Cu /CeO catalyst surface showed characteristic vibrational modes for surface-\n0.6 1 2\nbound *OH radicals (3568, 3627, and 3648 cm⁻1) and dissociative H O adsorption via\n2\nʋ(O–H) stretches (3670, 3701, and 3734 cm⁻1; Supplementary Fig. 49). These\nsignatures confirm hole-mediated H O dissociation pathway that supplies protons for\n2\n“10. Does O cause over-oxidation to Cu2+ during the oxidation process of Cu?”\n2\ninduces over-oxidation of Cu2+ during the reaction process. To rigorously verify this\npoint, we prepared a standardized compound CeO /CuO with well-defined Cu2+\n2\nvalence state as reference (ACS Energy Lett., 2021, 6, 893–899), and specifically\nsupplemented the fine Cu 2p XPS spectra of Ru Cu /CeO catalyst in the high\n0.6 1 2\nbinding energy region (~930–958 eV), where characteristic satellite peaks served as\nkey fingerprints for identifying Cu2+ (Supplementary Fig. 36). Analysis demonstrated\nthat:\n1. Reference sample CeO /CuO clearly showed strong satellite peaks near ~944 eV,\n2\nexplicitly confirming the existence of Cu2+;\n2. In sharp contrast, the corresponding spectra of Ru Cu /CeO catalyst\n0.6 1 2\nthroughout the entire reaction time window (0 to 120 min) always showed no\nobservable distinct satellite peak features;\n3. Additionally, the main peak binding energy position of Cu in Ru Cu /CeO\n0.6 1 2\nexhibited significant differences from the Cu2+ main peak in the reference sample,\nmore closely resembling characteristic values of Cu0/Cu1+.\nComprehensively considering the absence of satellite peaks, significant shift of\nmain peak binding energy position, and monitoring results across the full reaction\ntime series, we confirmed that no Cu2+ species was generated during the oxidation\nprocess on Ru Cu /CeO catalyst, thus eliminating the possibility of O causing\n0.6 1 2 2\nover-oxidation of Cu to Cu2+. These results have been incorporated into the revised\nmanuscript and are also attached below, with new content highlighted in yellow.\nSupplementary Fig. 36 | Cu 2p quasi in situ XPS spectra of CeO /CuO and\n0.6 1 2\n…The valence state of the Cu active sites was monitored using in situ X-ray\nphotoelectron spectroscopy (XPS). During the initial reaction phase under\nconcentrated solar irradiation (0–15 min), the Cu LMM Auger spectra exhibited only\nthe characteristic peaks of metallic Cu (Cu0; 918.6–919.4 eV). At 30 min, Cu1+\nspecies emerged (913.4–913.9 eV), and their relative abundance progressively\nincreased to 58% as the reaction proceeded further (Fig. 3f)23. No Cu2+ species were\ndetected in the higher binding energy range during the quasi in situ XPS analysis\n(Supplementary Fig. 36)…\nPreparation of catalysts CuO/CeO\n2\nmethod followed by calcination. Specifically, 1.5 mmol of Cu(NO ) ·3H O and 1.0\n3 2 2\nmmol of Ce(NO ) ·6H O were dissolved in 40 mL of an aqueous solution containing\n3 3 2\n2.3 M glycerol with vigorous stirring at room temperature. The resulting solution was\ntransferred to a Teflon-lined stainless-steel autoclave and hydrothermally treated at\n180 °C for 6 h. After cooling to ambient temperature, the solid product was recovered\nby centrifugation and washed repeatedly with absolute ethanol (≥3 times). The\nprecipitate was dried at 80 °C for 12 h under vacuum. The dried precursor was then\ncalcined in static air using a muffle furnace. The temperature was ramped to 350 °C at\n5 °C·min−1 and held for 2 h, yielding the final CuO/CeO catalyst.\n2\n“11. The discussion on the modulation mechanism by O\n2\nis lacking.”\nWe sincerely thank the Reviewer for the insightful and constructive comments on the\nO modulation mechanism, which are crucial for strengthening our study’s rigor. In\n2\nresponse, we have significantly expanded this discussion in the revised manuscript\n(originally lines 523-537). This includes adding specific molecular pathways involved\nand providing a more in-depth exploration of potential mechanisms of action. We are\nconfident these enhancements substantially strengthen the rigor and depth of this\nsection, fully addressing the Reviewer’s valuable concerns. These results have been\nincorporated into the revised manuscript and are also attached below, with new\ncontent highlighted in yellow.\nBuilding on an in-depth analysis of the photothermal CO reduction dynamic\n2\nmechanism, we reveal spatiotemporally ordered reconstruction of active interfaces in\nthe Ru Cu (Cu0–Cu1+)/CeO system (Fig. 5i). During the initial irradiation phase (t <\n0.6 1 2\n30 min), lattice-anchored single-atom Ru sites establish strong electronic metal-\nsupport interactions via a trigonal prismatic coordination configuration, accelerating\nH\nwith strongly adsorbed *CO intermediates via protonation; this dominates CH\n4\ngeneration. Concurrently, interfacial oxygen accumulates exponentially with time.\nUpon exceeding a critical threshold, O byproduct adsorb onto Cu0 sites and accept\n2\nsingle-electron transfer to form superoxide radicals. Subsequent O–O bond cleavage\nyields reactive atomic oxygen, which oxidizes Cu0 to Cu1+ via charge transfer. This\ntransformation induces selective oxidative etching and atomic rearrangement on\nRuCu alloy surfaces, driving self-assembly of a dynamic Cu0–Cu1+ heterointerface\nwith electron gradient distribution. This restructured interface shifts *CO intermediate\nfrom linear to bridging adsorption, redirecting products toward C products. In the\n2\ndeep reaction phase (30 ≤ t < 120 min), accumulated *CHOCO intermediates stabilize\nvia dual-site chelation: carbonyl carbon coordinates Cu1+, while aldehyde oxygen\nbinds adjacent Cu0 sites. This spatially confined adsorption reduces the *CHOCO →\n*CH OCO hydrogenation barrier, dynamically regulates intermediates coverage, and\n2\nsuppresses competing side-reaction pathways. Collectively, this dynamic mechanism\nshows how the photothermal coupling effect can control the product selectivity by\nregulating active sites, both spatially and temporally, as well as the distribution of key\nintermediates.\nReviewer #3:\n“1. This work demonstrates an oxygen engineering for activation of Cu0-Cu+ pairs\nfurther for the photoreduction CO to C H . The performance on this configuration\n2 2 4\nshows an impressive activity in the field of C H production from CO . Moreover,\n2 4 2\nplentiful DFT simulation provides an evident support for the dynamic reconstruction\nof Cu0-Cu+ pairs hypothesized in this work. This concept is interesting, and the\nstrategy provides a feasible route for the photocatalyst design. However, some\nconcerns should be further clarified prior to published. Specific issues are as follows:”\nWe are grateful to the Reviewer for the overall positive feedback on our work and for\nthe valuable suggestions and comments. We have diligently addressed each of these\ncomments in a point-by-point manner and have incorporated additional contents into\nthe revised manuscript and corresponding Supplementary Information.\n“2. As discussed in XAFs session, the valence state of Ru seems between 0 and +4, as\nshown in figure 2q and 2r, why the author made the analysis of d-p hybridization by\nRu2+? How to make sure +2? The analysis of Ru filed seem upon the octahedral field, is it fitting for the pentahedral? Additionally, similar to Cu+, result shows Cu is metallic state (Cu0), why use Cu+? And if Cu+, the e is fully filled by the electrons,\ng\nhow to bonding by d-p? If no COHP analysis of individual of d orbitals with p, how to\nconclude dz2 or dx2-y2 or dxz…?”\nWe sincerely thank the Reviewer for this insightful and expert comments, which have\nsignificantly improved our manuscript. All issues raised regarding the valence states\nof Ru and Cu, the limitations governing the applicability of the ligand field model,\nand the specifics of the bonding interaction analysis have been incorporated into the\nrevised manuscript, with new content highlighted in yellow.\n1. The valence states of Ru and Cu\nThe reviewer correctly noted that the XANES data suggested a Ru valence state\nbetween 0 and +4. Our assignment of Ru2+ was based on two consistent lines of\nevidence: (i) Bader charge analysis yielded a Ru charge of 6.40 e⁻, closely matching\nthe 6.00 e⁻ value expected for Ru2+; and (ii) Synchrotron-based XANES analysis at\nthe Ru K-edge (22,100–22,200 eV) used Ru foil (Ru0; K-edge threshold: ~22,113 eV)\nand RuO\n2\n(Ru4+; K-edge threshold: ~22,120 eV) as references. The normalized\nspectrum was processed using a Savitzky-Golay algorithm to obtain the first-\nderivative spectrum (ACS Catal., 2025, 15, 1–13; Nat. Catal., 2018, 2, 134–141). We\nassigned the global maximum of this derivative, located at ~22,116 eV, as the\nsample’s absorption edge energy. Applying the linear correlation between K-edge shift\nand oxidation state for transition metals, the average Ru oxidation state was calculated\nas +1.96 (Supplementary Fig. 9). This value was consistent with a +2 oxidation state\nwithin experimental error. For Cu, the Bader charge of 9.97 e⁻ aligned with Cu+ (10\ne⁻), which justified its use in bonding analysis.\n22120\nRuO (+4)\n2\n22118\nV) \ne 22116\nE\n(\n0.6 1 2\n22114\nRu foil (0)\n22112\n0 1 2 3 4\nOxidation state\nSupplementary Fig. 9 | The oxidation state of Ru Cu /CeO derived from the\n0.6 1 2\nnormalized X-ray absorption near-edge spectra at the Ru K-edge.\n…Ru K-edge X-ray absorption near edge structure (XANES) analysis demonstrated\nthat the absorption edge at ~22,116 eV was positioned between that of metallic Ru\nfoil (~22,113 eV) and an RuO reference material (~22,120 eV), confirming that the\n2\naverage oxidation state of the Ru species lies between the metallic (0) and +4 valence\nstates (Fig. 2f). Using the linear correlation between K-edge shift and oxidation state\nfor transition metals, we determined an average Ru oxidation state of +1.96\n(Supplementary Fig. 9)…\n2. The bonding mechanism of Cu+\nWe agree with the Reviewer that the filled d10 configuration of Cu+ precluded\nconventional covalent bonding via electron sharing. However, we clarified that the d10\nstate was not a precondition but rather resulted from electronic rearrangement\nfollowing Cu incorporation into the CeO lattice, which was consistent with the\n2\ncalculated Bader charge.\n3. The coordination environment\nWe thank the Reviewer for identifying the inaccuracies in our description of the\ncoordination environment, which has improved the structural rigor of our manuscript.\nOur initial use of “pentahedral coordination” reflected a geometric interpretation of\nthe triangular prism configuration. However, this characterization was imprecise: the\nRu atom occupied a standard trigonal prismatic ligand field formed by six oxygen\natoms—a configuration previously reported (Adv. Mater., 2021, 33, 2101788). We\ncorrected this terminology throughout the manuscript.\nGiven that trigonal prismatic configurations represented uncommon six-\ncoordination geometries, comprehensive ligand field models describing d-orbital\nsplitting behavior remained underdeveloped. To avoid ambiguity, we have removed\nthe original orbital interaction diagrams (Figs. 2q, 2r). The retained electronic\nstructure data conclusively supported our conclusions.\nFig. 2 | Structural and electronic characterization of Ru Cu /CeO . k, l, Ru–O\n0.6 1 2\ncoordination environment in Ru Cu /CeO (k) and Cu–O coordination environment\n0.6 1 2\nin Ru Cu /CeO (l) catalysts. m, n, Projected density of states analysis of Ru 4d–O\n0.6 1 2\n2p (m) and Cu 3d–O 2p (n) hybridization. o, p, Crystal orbital Hamiltonian\npopulation analysis of Ru–O bonds (o) and Cu–O bonds (p) in Ru Cu /CeO .\n0.6 1 2\n…Single-atom Ru doping at Ce lattice sites creates a trigonal prismatic coordination\nconfiguration, enabling proton-coupled electron transfer and accelerating H O\n2\ndissociation…\n…Theoretical calculations and in situ characterizations confirmed that the Ru single\natoms substitute Ce lattice sites to form a trigonal prismatic coordination\nconfiguration, which induces proton-coupled electron transfer to maintain efficient\nhydrogen spillover…\n…In the optimized structure, Ru atoms occupying Ce sites via lattice substitution\nadopt a trigonal prismatic coordination with six neighboring O atoms, exhibiting a\nformation energy (E ) of −7.02 eV (Fig. 2k)…\nform\n…During the initial irradiation phase (t < 30 min), lattice-anchored single-atom Ru\nsites establish strong electronic metal-support interactions via a trigonal prismatic\ncoordination configuration, accelerating H\nmigrates to alloy cluster surfaces, coupling with strongly adsorbed *CO intermediates\nvia protonation; this dominates CH generation…\n4\n…Our findings show that single-atom Ru substitutions at Ce lattice sites create a\ndistorted a trigonal prismatic coordination field, which promotes proton-coupled\nelectron transfer, thereby accelerating H O dissociation…\n2\n4. The conclusion of the relative stability of Ru vs. Cu doping\nThe higher coordination number and structural integrity of the Ru site (six-coordinate\ntrigonal prismatic configuration) compared to Cu (four-coordinate square planar\nconfiguration) suggested greater stability for Ru. This was confirmed by formation\nenergy calculations: Ru doping exhibited a formation energy of –7.02 eV,\nsignificantly lower than that of Cu (–4.12 eV). To further validate this, we\nrecalculated all projected density of states (PDOS) and crystal orbital Hamilton\npopulation (COHP) curves for the doped Ru/Cu atom and its seven neighboring\noxygen atoms. The updated results revealed a narrower band center offset between Ru\nand O (~0.21 eV) than between Cu and O (~0.37 eV), indicating stronger\nhybridization and covalency. Integrated COHP (ICOHP)values below the Fermi level\nwere also more negative for Ru–O (–0.63) than for Cu–O (–0.13), confirming\nstronger bonding stability. These results aligned with the formation energies.\nWe conclude that the electronic structure analysis and formation energy data in our\nrevised manuscript consistently demonstrate that Ru doping is thermodynamically and\nelectronically more favorable than Cu doping. The removal of orbital diagrams does\nnot affect the core conclusions.\nFig. 2 | Structural and electronic characterization of Ru Cu /CeO . k, l, Ru–O\n0.6 1 2\ncoordination environment in Ru Cu /CeO (k) and Cu–O coordination environment\n0.6 1 2\nin Ru Cu /CeO (l) catalysts. m, n, Projected density of states analysis of Ru 4d–O\n0.6 1 2\n2p (m) and Cu 3d–O 2p (n) hybridization. o, p, Crystal orbital Hamiltonian\npopulation analysis of Ru–O bonds (o) and Cu–O bonds (p) in Ru Cu /CeO .\n0.6 1 2\nProjected density of states (PDOS) analysis revealed distinct electronic coupling\nbehaviors of the doped Ru and Cu with their seven neighboring O atoms on the\nCeO (111) surface. The band center difference between the O 2p and Ru 4d orbitals\n2\n(Δ = | −  |) is 0.21 eV for spin up and down orbit smaller than that between\n2p(O) 4d(Ru)\nthe O 2p and Cu 3d orbitals (Δ = | −  |, about 0.37 eV), indicating the\n2p(O) 3d(Cu)\nrelatively more substantial rehybridization between the Ru 4d and O 2p orbitals (Figs.\n2m and 2n). Crystal orbital Hamilton population (COHP) analysis further revealed the\nnature of the Ru–O and Cu–O bonds22. It was found that electrons primarily occupy\nthe bonding states of Ru–O bonds, while the antibonding state was rarely occupied.\nFor Cu–O bonds, however, electrons occupied both bonding and antibonding states\n(Figs. 2o and 2p). The much more negative values of the integrated COHP (ICOHP)\nfor Ru–O bonds (−0.63) than that for Cu–O bonds (−0.13) indicated the relatively\nstronger bonding between Ru and the coordinated O atoms. Overall, integrated DFT\nmodeling and electronic structure analysis consistently demonstrate that doped Ru\nsingle atom is a thermodynamically more favorable and stable dopant than Cu atom in\nthe CeO (111) surfaces.\n2\n“3. How to confirm the substitution between Ru and Ce, instead of atomic surface\nanchor or doping into the lattice of cerium oxides? Any evidence?”\nWe sincerely thank this Reviewer for this professional comment. To identify Ru\nspecies within the CeO support, XRD diffractograms of pure CeO and the\n2 2\nRu /CeO catalyst were compared with fluorite-phase CeO reference data (PDF#43-\n0.6 2 2\n1002). Critical evidence indicated that: (1) The absence of Ru-related diffraction\npeaks confirmed atomic dispersion below the XRD detection limit, precluding\ncrystalline phase formation. (2) A systematic ~0.15° high-angle shift in major\ndiffraction peaks (vs. pure CeO ; Supplementary Fig. 6) corresponded to a ~0.015 Å\n2\nlattice contraction, calculated using Bragg’s law (Adv. Mater., 2024, 36, 2405970; J.\nAm. Chem. Soc., 2025, 147, 22806–22817; Nat. Commun., 2019, 10, 2149). This\ncontraction arose from substitution of Ce4+ by smaller Ru3+ ions, inducing anisotropic\ncompression of the fluorite unit cell. This mechanism excluded non-lattice pathways\n(e.g., surface anchoring/physisorption).\nAtomic-resolution AC-HAADF-STEM directly visualized Ru atoms occupying Ce\nlattice sites along the [111] zone axis (Profile 1 region) (Supplementary Fig. 5). Line-\nscan profiles matched local lattice distortion/contraction. Collectively, XRD-\nquantified lattice contraction and AC-STEM-observed atomic substitution confirmed\nRu doping at CeO fluorite lattice sites. The revised manuscript and Supplementary\nbackground.\nSupplementary Fig. 6 | XRD patterns of CeO and Ru /CeO .\n2 0.6 2\nSupplementary Discussion: A systematic ~0.15° high-angle shift in major diffraction\npeaks (vs. pure CeO ) corresponds to a ~0.015 Å lattice contraction, calculated using\ninducing anisotropic compression of the fluorite unit cell. This mechanism excludes\nnon-lattice pathways (e.g., surface anchoring/physisorption).\nSupplementary Fig. 5 | HAADF-STEM image of Ru /CeO . The illustration shows\n0.6 2\nthe line-scan intensity profiles across positions 1.\n…To analyze the distribution patterns of metallic Ru and Cu on the CeO support,\n2\nthree-dimensional conformational characterization of Ru Cu /CeO was conducted\n0.6 1 2\nusing atomic-resolution HAADF-STEM (Co-existence of monatomic Ru and Ru/Cu\nalloy). The results revealed that Ru atoms were stably anchored on the CeO support\n2\nin a monoatomic dispersion with no detectable agglomeration (Fig. 2b). Direct\nimaging further visualized Ru atoms occupying Ce lattice sites along the [111] zone\naxis (Supplementary Fig. 5), with line-scan profiles confirming localized lattice\ncontraction. Additionally, XRD patterns indicated that Ru doping induced a\nsystematic high-angle shift of ~0.15° in the main diffraction peaks (Supplementary\nFig. 6). This lattice contraction resulted from substitution of smaller Ru3+ ions for\nCe4+ ions, causing anisotropic compression of the fluorite unit cell. Sub-nanoscale\nalloy clusters (1–3 nm) were also observed on the support surface (Fig. 2c and\nSupplementary Fig. 7)…\n“4. Regarding to the in situ XPS analysis in figure 3f, how’s the change of Cu0 and\nCu+ species change after remove irradiation? Will recover thermodynamical\nequilibrium?”\nWe sincerely thank the Reviewer for this insightful comment. Quasi in situ XPS\nanalysis of Ru Cu /CeO clarified the catalyst’s post-irradiation evolutionary\n0.6 1 2\nbehavior (Supplementary Fig. 42): Surface Cu species maintained a stable Cu0–Cu1+\nconfiguration upon light cessation without reverting to their pre-irradiation state.\nThis confirmed that O mediated dynamic interfacial reconstruction during reaction.\n2\nfrom transient photogenerated metastable states or reversible thermodynamic\nequilibria. The persistent structural memory—formed under non-equilibrium\nconditions yet retained at equilibrium—established the Cu0–Cu1+ interface as an\nintrinsic, stable active component. We proposed that this autonomously generated\nsynergistic interface, stabilized in situ within the O -participating environment,\n2\nconstituted the essential active site for C–C coupling. The revised manuscript and\nSupplementary Information now include additional content, which is distinguished by\na yellow background.\nSupplementary Fig. 42 | Cu 2p in situ XPS spectra of Ru Cu /CeO catalyst under\n0.6 1 2\ndifferent conditions.\n…Scanning electron microscopy confirmed that the catalyst morphology was\npreserved after cycling, indicating that the lattice is structurally stable under high-\ntemperature reaction conditions (Supplementary Fig. 41). In situ XPS analysis\nrevealed that surface Cu species maintain a stable Cu0–Cu1+ configuration upon\nillumination cessation without reverting to their pre-irradiation state (Supplementary\nFig. 42). Critically, this O -induced reconstruction persists post-irradiation,\n2\ndistinguishing it from transient photogenerated metastable states and reversible\nthermodynamic equilibria. The persistent structural memory—formed non-\nequilibrium but retained at equilibrium—establishes the Cu0–Cu1+ interface as an\nintrinsically stable active component…\n“5. For the controlled performance, it’s wired that nothing productivity was obtained\nby sole UV and thermocatalysis in figure 3d, what’s the reason behind? Particularly\nunder UV, temperature probably will not be up to ~462 ℃ under UV, alternatively,\nif keep the system at ~462 ℃ and then add UV irradiation, what happens?”\nWe sincerely thank the Reviewer for this valuable comment. As correctly noted,\nefficient conversion of CO and H O vapour into C hydrocarbons (e.g., C H ) via\n2 2 2+ 2 4\nconventional thermal catalysis typically required temperatures significantly exceeding\n800 °C—substantially higher than those employed here. This consensus was well-\nestablished in authoritative literature (J. Am. Chem. Soc., 2025, 10.1021/jacs.5c11625;\nNat. Commun., 2024, 15, 4675; Prog. Energy Combust. Sci., 2019, 74, 1–30; ACS\nNano, 2024, 18, 13035–13048). In this work, the maximum catalyst temperature\nachieved via photothermal synergy was 461.5 °C, over 300 °C below this thermal\ncatalysis threshold. Consequently, no C H formation was observed in control\n2 4\nexperiments under UV irradiation alone (incapable of reaching ~462 °C) or thermal\ncatalysis alone at 462 °C.\nAccording to the Reviewer’s comment, precise experimental validation under\ncontrolled conditions (462 °C, UV: 50–250 mW·cm−2) confirmed no detectable C H\n2 4\nproduction, even with combined thermal and photonic activation (Supplementary Fig.\n30). The fundamental limitation arose because C H generation required exceeding a\n2 4\nthreshold O concentration in the reaction environment—neither temperature nor\n2\nphotoexcitation alone drove the process. Mechanistic studies revealed that insufficient\nO failed to dynamically form and sustain the essential Cu0–Cu1+ active interface on\n2\nthe catalyst surface, which was indispensable for C–C coupling. Consequently, neither\nthermal activation alone, UV irradiation alone, nor their combination—under\nconditions where photo-induced charge carriers could not drive water oxidation or O\n2\nconcentrations remained sub-threshold—established this catalytic interface, thereby\npreventing C H pathway initiation. The revised manuscript and Supplementary\n2 4\nInformation now include additional content, which is distinguished by a yellow\nbackground.\nSupplementary Fig. 30 | Catalytic performance for CO reduction under varying UV\n2\nirradiation intensities at 462 °C via external heating.\n…(2) Maintaining temperature at 462 °C while irradiating with lower-intensity UV\nlight (50–250 mW·cm−2) also yielded no C H (Supplementary Fig. 30). Control\n2 4\nexperiments—including systems without H O, CO , or catalytic components—\n2 2\nsimilarly demonstrated no C H signals…\n2 4\n“6. From the result of 3 W/cm2 in Figure 3, the phenomenon is interesting. What’s the\nreason or mechanism behind, why 3 W/cm2 is the on-set switch of C H production?\n2 4\nIf control the reaction system temperature without irradiation at the same as 3 W/cm2,\nan illumination-progressed (such as 50 mW/cm2, 100 mW/cm2, 300 mW/cm2, et al.)\nperformed under the similar condition, will C\n4\nproduced?”\nWe are grateful to the reviewer for the thoughtful comments and questions. The core\nmechanism establishing 3.00 W·cm−2 as the critical irradiance for C H generation lay\n2 4\nin the photothermal synergy achieved at this intensity. This synergy drove water\ndissociation, producing O at 550 μmol·g−1—sufficient to oxidize surface Cu0 in situ,\n2\nforming the essential Cu0–Cu1+ active interface that mediated C–C coupling and\ndirectly controlled C H formation. Below 3.00 W·cm−2, O production was\n2 4 2\ninsufficient to drive the Cu0-to-Cu1+ transition, preventing interface formation. To\nverify this, we used infrared thermography to measure a catalyst surface temperature\nof 298.6 °C under 3.00 W·cm−2 irradiation. We then replicated these thermal\nconditions (298.6 °C) with auxiliary illumination (50–300 mW·cm−2). Crucially, no\nC H was produced despite equivalent thermal energy and auxiliary light\n2 4\n(Supplementary Fig. 38), confirming O concentration as the decisive bottleneck:\n2\nslow O generation kinetics below the critical irradiance failed to overcome the\n2\nactivation barrier for Cu0–Cu1+ interface formation, thereby blocking the C H\n2 4\npathway.\nThis demonstrated photon flux’s specific regulatory role in photothermal catalysis.\nOnly at the critical irradiance were both thermodynamic (temperature) and kinetic (O\n2\nconcentration) requirements simultaneously satisfied to enable the reaction pathway.\nThe revised manuscript and Supplementary Information now include additional\ncontent, which is distinguished by a yellow background.\nSupplementary Fig. 38 | Catalytic performance for CO reduction under varying full-\n2\nspectrum irradiation intensities at 298.6 °C via external heating; infrared\nthermographic image shows surface temperature distribution under 3 W·cm−2\nconcentrated solar irradiation.\nIn concentrated solar irradiation regulation experiments (10–60 suns, 1 sun (100\nmW·cm−2)), the O generation rate was positively correlated with the irradiation\n2\nintensity (Fig. 3g). However, C H production exhibited light-intensity-dependent\n2 4\nnonlinear behavior with a distinct threshold. C H formation commenced at 30 suns\n2 4\n(298.6 °C), achieving 7.3% selectivity and O yield of 550 mol·g−1. Under identical\n2\nthermal conditions with auxiliary illumination (50–300 mW·cm−2), no C H formation\n2 4\nwas observed (Supplementary Fig. 38). This confirms that O concentration is the\n2\nprimary limiting factor. At 50 suns, the C H selectivity had increased 10-fold to\n2 4\n74.3%. This nonlinear amplification effect causes a 25-fold enhancement in the solar-\nto-chemical energy conversion efficiency (0.5% vs. 0.02% for that under non-\nconcentrated solar irradiation, Supplementary Table 5)…\n“7. The configuration of Ru Cu /CeO proposed in this work is Ru single atoms with\nx y 2\nRuCu sub-alloy. How’s performance of the Ru SAs+Cu SAs/CeO , and Ru SAs+Cu\n2\nsub-alloy/CeO ?”\nsequential impregnation-calcination: a dual single-atom catalyst (Ru SAs + Cu\nSAs/CeO ) and a catalyst with coexisting Ru single atoms and Cu sub-nanoclusters\n2\n(Ru SAs + Cu sub-nanocluster/CeO ). Aberration-corrected HAADF-STEM\n2\nconfirmed that on CeO (111), the former achieved uniform Ru/Cu single-atom co-\n2\ndispersion, while the latter formed Ru single atoms alongside subnanometer Cu\nclusters (Supplementary Fig. 25). Under concentrated solar irradiation, neither control\ncatalyst produced C H ; photothermal CO reduction yielded only CO and CH\n2 4 2 4\n(Supplementary Fig. 26). This sharply contrasted with the high ethylene selectivity of\nour primary catalyst, Ru Cu (Cu0–Cu1+)/CeO . Thus, these controlled experiments\n0.6 1 2\ndemonstrated that efficient and selective C H production in the Ru Cu /CeO\n2 4 0.6 1 2\nsystem required Ru–Cu intermetallic interactions mediated by specific alloy structures.\nThe revised manuscript and Supplementary Information now include additional\ncontent, which is distinguished by a yellow background.\nSupplementary Fig. 25 | a, b HAADF-STEM image of Ru SAs + Cu SAs/CeO (a)\n2\nand Ru SAs + Cu sub-nanocluster/CeO (b).\n2\n(5000 mW·cm−2).\n…The Ru Cu /CeO catalyst exhibited distinct product selectivity owing to this\n0.6 1 2\nenergy-field coupling, with a C H production rate of 274.5 mol·g−1·h−1 and\n2 4\nconcurrent O evolution rate of 910.5 mol·g−1·h−1 (Fig. 3b, Supplementary Fig. 23\n2\nand Supplementary Table 4). This sacrificial agent system did not significantly\nenhance catalytic performance (Supplementary Fig. 24). The fundamental limitation\nstems from inherent differences between gas–solid systems and conventional liquid-\nphase reactions. In contrast, a dual single-atom catalyst (Ru SAs + Cu SAs/CeO ) and\n2\na catalyst with coexisting Ru single atoms and Cu sub-nanoclusters (Ru SAs + Cu\nsub-nanocluster/CeO ) yielded only CO and CH during photothermal CO reduction\n2 4 2\n(Supplementary Figs. 25 and 26). Notably, this corresponds to a significant\nenhancement in C H selectivity from 0% to 74.3% compared with that under non-\n2 4\nconcentrated solar irradiation, with electron selectivity reaching 91.4%.\nPreparation of catalysts Ru SAs + Cu SAs/CeO\n2\nwater under magnetic stirring (600 rpm) for 1 h. Subsequently, 13 mg of RuCl ·xH O\n3 2\nand 18 mg of CuCl were added to achieve target metal loadings, with stirring (600\n2\nrpm) continued for 12 h to ensure thorough precursor adsorption. The precursor\nsolution was vacuum-dried at 70 °C for 12 h. The precursor underwent temperature-\nprogrammed reduction in a tube furnace under 50 mL·min−1 of high-purity 5% H /Ar:\n2\nheating from 25 °C to 400 °C at 5 °C·min−1, then holding at 400 °C for 2 h to form\nhighly dispersed single-atom sites. After cooling to room temperature under Ar, the\nsample was collected for use.\nPreparation of catalysts Ru SAs + Cu sub-nanocluster/CeO\n2\ncalcination. First, 800 mg of pre-synthesized CeO support was dispersed in 30 mL of\n2\ndeionized water under magnetic stirring (600 rpm) for 1 h. Subsequently, 13 mg of\nRuCl ·xH O and 90 mg of CuCl were added to achieve target metal loadings, with\n3 2 2\nstirring (600 rpm) continued for 12 h to ensure thorough precursor adsorption. The\nprecursor solution was vacuum-dried at 70 °C for 12 h. The precursor underwent\ntemperature-programmed reduction in a tube furnace under 50 mL·min−1 of high-\npurity 5% H /Ar: heating from 25 °C to 500 °C at 5 °C·min−1, then holding at 500 °C\n2\nfor 2 h to form highly dispersed single-atom sites. After cooling to room temperature\nunder Ar, the sample was collected for use.\n“8. As the proposed pathway of OER in Figure S12, is there any H O in the solution?\n2 2\nWhat’s the function of holes in the proposed reaction system? How it will happen if\nsome sacrificer (like function for h+ and ·OH quenching) added during CO RR.”\nyou identified—regarding the presence of H O in the OER pathway, the mechanistic\n2 2\nrole of holes (h+), and the potential implications of introducing sacrificial agents (e.g.,\nh+/·OH scavengers) for the CO RR process—we conducted exhaustive validation and\n2\nmechanistic exploration through rigorously designed experiments. Relevant\nexperimental data, analytical findings, and their alignment with the proposed reaction\npathway have been systematically integrated into the supplementary materials and\ndiscussed in depth.\nTo rigorously verify whether oxygen undergoes further reduction during the\nCO RR, we performed catalytic experiments under concentrated solar irradiation. A\n2\ncirculating water-cooling system maintained a constant temperature at the reactor’s\ninner wall, effectively suppressing potential thermal decomposition of hydrogen\nperoxide (H O ; 2H O → O + 2H O). Post-reaction, we injected 30 mL high-purity\n2 2 2 2 2 2\ndeionized water (18.2 MΩ·cm) quantitatively through a septum. The system was\nvortex-mixed (200 rpm, 3 min) to desorb species and enable quantitative transfer of\nwall-adsorbed products into the aqueous phase (Supplementary Fig. 27a). Critically,\npost-extraction analysis detected no quantifiable H O (Supplementary Fig. 27b),\n2 2\nindicating that detectable O reduction to H O did not occur under these conditions.\n2 2 2\nThis result aligns with the inherent limitations of direct H O synthesis in gas-phase\n2 2\nsystems (Energy Environ. Sci., 2024, 18, 6482–6498; Chem. Soc. Rev., 2020, 49,\n6605–6631; Adv. Mater., 2024, 36, 2412386).\nSupplementary Fig. 27 | a Operational schematic of a photoreactor assembly for\nphotothermal catalytic H O production. b Yield diagram for different catalysts under\n2 2\nconcentrated solar irradiation.\nPhotocatalytic H O production\n2 2\nAfter photo-thermal catalytic CO reduction, 30 mL high-purity deionized water (18.2\ncirculator (5.0 ± 0.1°C) minimized thermal degradation of H O . Components\n2 2\nadhering to reactor walls were fully dissolved in the aqueous phase by vortex mixing\n(200 rpm, 3 min), ensuring quantitative product recovery. H O concentration was\n2 2\nthen quantified via standardized iodometric titration.\nMeasurement of H O concentration\n2 2\nH O concentration was determined using a standardized iodometric method39. Briefly,\n2 2\n1 mL 0.1 M potassium hydrogen phthalate (C\n4\n) aqueous solution was added to\nthe sample, followed by 1 mL of 0.4 M potassium iodide (KI) aqueous solution. After\na 30 min reaction period, H O reacted with iodide anions (I−) under acidic conditions\n2 2\naccording to the reaction: H O + 3I− + 2H+ → I − + 2H O, producing triiodide anions\n2 2 3 2\n(I −) that exhibit strong absorption at 350 nm. I − concentration was quantified using\n3 3\nUV-Vis spectroscopy, allowing calculation of the H O concentration generated.\n2 2\nReferences\nsustainable photocatalytic H O generation. Angew. Chem. Int. Ed. e202508718\n2 2\n(2025).\n…This C → C transition aligns with the Langmuir–Hinshelwood surface reaction,\n1 2\nindicating that there is dynamic competition between the C H formation pathways\n2 4\nand consumption of CO intermediates. To rigorously verify if oxygen is further\nreduced during CO reduction, we performed catalytic experiments under\n2\nconcentrated solar irradiation. Post-extraction analysis detected no quantifiable H O\n2 2\n(Supplementary Fig. 27). Mass spectrometry-calibrated and baseline-corrected gas\nchromatography data validated the concurrent enhancement of C H selectivity with\n2 4\nCO conversion (Supplementary Figs. 28 and 29)…\nUnder concentrated solar irradiation (AM 1.5G, 5000 mW·cm⁻2), Operando\nDRIFTS analysis of CO /H O co-adsorption revealed in situ formation of\n2 2\nintermediates during 120 min illumination. The Ru Cu /CeO catalyst surface\n0.6 1 2\nshowed characteristic vibrational modes for surface-bound *OH radicals (3568, 3627,\nand 3648 cm⁻1) and dissociative H O adsorption via ʋ(O–H) stretches (3670, 3701,\n2\nand 3734 cm⁻1; Supplementary Fig. 49) (Nat. Commun., 2024, 15, 4675; Nano energy,\n2023, 113, 108578; Angew. Chem. Int. Ed., 2024, 63, e202410474). These signatures\nconfirm hole-mediated H\n2\nreduction. This evidence validates the kinetic relevance of the four-step H O\n2\noxidation mechanism, as captured through the observed intermediates (Supplementary\nFig. 50). As shown:\n(1) H O + * + h+ → *OH + H+\n2\n(2) *OH + h+ → *O + H+\n(3) *O + H O + h+ → *OOH + H+\n2\n(4) *OOH + h+ → O + H+ + *\n2\n* represents the active site.\nSupplementary Fig. 49 | Operando DRIFTS of H O activation intermediates on\n0.6 1 2\nThe reaction cascade occurs through four concerted steps:\n1. H O adsorption and oxidation:\n2\nhydroxyl species (*OH) while releasing a proton (H+).\n2. Hydroxyl oxidation:\n*OH + h⁺ → *O + H+\nSubsequent hole oxidation deprotonates *OH, yielding adsorbed atomic oxygen (*O)\nand a H+.\n3. O–O bond formation:\n*O + H O + h⁺ → *OOH + H+\n2\nadsorbate (*OOH), releasing a third H+.\n4. O liberation:\n2\n*OOH + h⁺ → O + H+ + *\n2 2\nIn a concentrated solar-driven gas–solid CO reduction reaction system, 0.35 M\n2 2 3\nrecombination by photogenerated holes (h+) and competitive hydroxyl radical (·OH)\noxidation (Adv. Funct. Mater., 2025, n/a, 2506159; J. Am. Chem. Soc., 2024, 146,\n4068–4077; Nano Energy, 2025, 136, 110750). However, this sacrificial agent system\ndid not significantly enhance catalytic performance (Supplementary Fig. 24). The\nfundamental limitation stemmed from inherent differences between gas–solid\nsystems and conventional liquid-phase reactions: When physically separated from\nthe solid catalyst, it prevented maintenance of effective scavenger concentrations at\nthe gas–solid–liquid triphasic interface. Simultaneously, the liquid-phase\nmechanism—dependent on bulk diffusion of scavengers to capture holes—was\nseverely constrained. Conversely, in gas–solid systems, photogenerated holes were\nneutralized predominantly through surface oxidation pathways. Due to prohibitive\ndiffusion/mass transfer limitations and microenvironmental instability—specifically,\nthe inability to sustain required concentration gradients—sacrificial agents could not\neffectively perform their intended role. The revised manuscript and Supplementary\nInformation now include additional content, which is distinguished by a yellow\nbackground.\nSupplementary Fig. 24 | Photocatalytic CO reduction activity under concentrated\n2\nsolar irradiation in the presence and absence of sacrificial reagents.\n…The Ru Cu /CeO catalyst exhibited distinct product selectivity owing to this\n0.6 1 2\nenergy-field coupling, with a C H production rate of 274.5 mol·g−1·h−1 and\n2 4\nconcurrent O evolution rate of 910.5 mol·g−1·h−1 (Fig. 3b, Supplementary Fig. 23\n2\nand Supplementary Table 4). This sacrificial agent system did not significantly\nenhance catalytic performance (Supplementary Fig. 24). The fundamental limitation\nstems from inherent differences between gas–solid systems and conventional liquid-\nphase reactions…\n“9. How’s the charge dynamics performance of the photocatalysts?”\nWe sincerely thank the Reviewer for this comment. Integrated analysis of steady-\nstate/transient spectroscopy, photoelectrochemistry, and impedance confirmed that\nRu\n0.6\nCu\n1\n(Cu0–Cu1+)/CeO\n2\noptimized charge carrier dynamics: (1) It exhibited the\nweakest steady-state photoluminescence (PL) intensity (Supplementary Fig. 43a),\ndemonstrating that the Cu0–Cu1+ charge-gradient interface effectively suppressed\nradiative recombination; (2) Time-resolved PL (Supplementary Fig. 43b) revealed a\nsubstantially longer average decay lifetime (5.62 ns) vs. reference samples (CeO :\n2\n2.98 ns; Ru /CeO : 3.45 ns; Cu /CeO : 3.76 ns; Ru Cu /CeO : 5.36 ns),\n0.6 2 1 2 0.6 1 2\nreflecting interface-dominated non-radiative pathways and enhanced electron-hole\nseparation; (3) A significantly enhanced photocurrent response (Supplementary Fig.\n43c) and reduced charge-transfer resistance (EIS; Supplementary Fig. 43d) indicated\nefficient carrier separation and migration at the interface. Collectively, the Cu0–Cu1+\ncharge-gradient interface promoted spatial separation of photogenerated carriers,\nsuppressed bulk/surface recombination, and accelerated migration to reactive sites.\nThese optimized dynamics formed the kinetic foundation for the exceptional photothermal\nCO reduction performance of Ru Cu (Cu0–Cu1+)/CeO . The revised manuscript and\n2 0.6 1 2\nSupplementary Information now include additional content, which is distinguished by\na yellow background.\nSupplementary Fig. 43 | a PL spectra. b TRPL spectra. c Transient photocurrent\nresponses. d EIS Nyquist plots.\nSupplementary Discussion: Integrated analysis of steady-state/transient spectroscopy,\nphotoelectrochemistry, and impedance confirmed that Ru Cu (Cu0–Cu1+)/CeO\n0.6 1 2\noptimizes charge carrier dynamics: (1) It exhibits the weakest steady-state PL\nintensity (Supplementary Fig. 43a), demonstrating that the Cu0–Cu1+ charge-gradient\ninterface effectively suppresses radiative recombination; (2) Time-resolved PL\n(Supplementary Fig. 43b) reveals a substantially longer average decay lifetime (5.62\nns) vs. reference samples (CeO : 2.98 ns; Ru /CeO : 3.45 ns; Cu /CeO : 3.76 ns;\n2 0.6 2 1 2\nRu Cu /CeO : 5.36 ns), reflecting interface-dominated non-radiative pathways and\n0.6 1 2\nenhanced electron-hole separation; (3) A significantly enhanced photocurrent response\n(Supplementary Fig. 43c) and reduced charge-transfer resistance (EIS; Supplementary\nFig. 43d) indicate efficient carrier separation and migration at the interface.\nCollectively, the Cu0–Cu1+ charge-gradient interface promotes spatial separation of\nphotogenerated carriers, suppresses bulk/surface recombination, and accelerates\nmigration to reactive sites.\n…The persistent structural memory—formed non-equilibrium but retained at\nequilibrium—establishes the Cu0–Cu1+ interface as an intrinsically stable active\ncomponent. The interfacial charge dynamics of the Ru\n0.6\nCu\n1\n(Cu0–Cu1+)/CeO\n2\ncatalyst\nwere elucidated in Supplementary Fig. 43.\n“10. More details of experiments session should be provided, in particular the in situ\ntechniques including XPS and DRIFTS, more details of experimental procedure\nshould be given clearly.”\nWe sincerely thank the Reviewer for the valuable suggestion and fully recognize the\nessential role of clearly documenting methodological details to validate research\nconclusions and enable replication. The revised manuscript now includes additional\ncontent, which is distinguished by a yellow background.\nQuasi-in situ XPS\nRu\n0.6\nCu\n1\n/CeO\n2\nsamples (50 mg per time point) were irradiated under concentrated\nsolar light (AM 1.5G spectrum; 5000 mW·cm−2) using a PerfectLight PLS-SXE\n300/300UXE solar simulator. Reactions occurred in a 1 vol% CO /N (99.999%)\n2 2\natmosphere with 1 mL H O for 0, 15, 30, 60, and 120 min. Post-irradiation, samples\n2\nwere transferred to an N glovebox, homogenized with 10 mg of spectroscopically\n2\npure graphite powder (<20 m particle size) in an agate mortar to mitigate charging\neffects, and densely packed into a sample holder. XPS spectra were acquired at room\ntemperature in a Thermo Scientific ESCALAB 250Xi spectrometer (base pressure ≤ 5\n× 10−8 mbar). All binding energies were charge-corrected and referenced to the\ngraphite C 1s peak at 284.8 eV, ensuring cross-comparability across the batch.\nOperando DRIFTS\nIn an operando DRIFTS system (Bruker TENSOR II spectrometer) equipped with a\nhigh-temperature, high-pressure diffuse reflectance cell, 50 mg of Ru Cu /CeO\n0.6 1 2\ncatalyst powder was dispersed on a spectroscopic-grade IR-transparent window. The\nsample was purged in situ with ultra-high-purity (UHP) N (≥99.999%, 50 sccm) at\n2\n25 °C for 30 min to remove physically adsorbed impurities and moisture; baseline\nstability was confirmed by real-time IR monitoring. The gas flow was then switched\nto a reaction mixture of CO /N balanced gas (controlled by calibrated mass flow\n2 2\ncontrollers, MFCs) co-fed with H O vapour (via a bubbler). All streams were\n2\npremixed in heated transfer lines before entering the cell. Upon introducing the\nreaction gas and activating the solar simulator (PerfectLight PLS-SXE 300/300UXE\nAM 1.5G spectrum; 5000 mW cm−2) simultaneously—defining t = 0 min as the\nreaction start—collimated irradiation was delivered through the cell’s top window\nonto the catalyst via a Fresnel lens focusing system (focal length: 30 cm). Operando\nDRIFTS data acquisition commenced immediately using the stabilized N -purged\n2\nspectrum as the background reference, collecting single-beam spectra at 4 cm−1\nresolution with 256 co-added scans per measurement. Absorbance spectra were\nrecorded at t = 0, 15, 30, 45, 60, 90, and 120 min under continuous\nreaction/irradiation to track surface intermediate evolution.\nDetails of the photothermal catalytic CO reduction\nsteel reactor (100 mL) equipped with a quartz window and Fresnel lens optics (30 cm\nfocal length), integrated with a solar simulator (PLS-SXE 300/300UXE, PerfectLight)\nproviding calibrated AM 1.5G irradiation (5000 mW·cm−2). Prior to the reaction, the\nsystem was purged with N (99.999%, 50 mL·min−1, 10 min) followed by charging\n2\nwith CO /N mixture (1 vol%, Praxair). Water vapour was introduced by injecting\n2 2\ndeionized water quantitatively (1 mL, 18.2 MΩ·cm resistivity) via a gas-tight syringe.\nDuring the reaction, the focused light spot generated simultaneous photoexcitation\nand localized thermal effects on the catalyst surface, enabling photothermal\nsynergistic catalysis. Gaseous products were analyzed online and quantified using gas\nchromatograph (GC-8860) with thermal conductivity detector (TCD) and flame\nionization detector (FID), employing a Porapak Q packed column. All gaseous\ncomponents were quantified via multi-point calibration using NIST-traceable\nstandards (calibration curves exhibited linear correlation coefficients R2 > 0.999). The\ncatalyst was continuously irradiated for 2 h with periodic sampling. Dark controls and\nadditional control experiments were conducted concurrently to rigorously exclude\nbackground interference and verify result reliability.\n“11. The author presents 34 district configurations in the figure 1f, the profiles of\ntheir energy seem to arrange from less to more following the arrow. And the Ru Cu\n3 5\nseems to be highlight. What’s the different configuration in the red dashed box, are\nthey same as Ru Cu ? If same, what’s the differences among them?”\n3 5\nWe sincerely thank this Reviewer for the proof-reading of our manuscript. In Figure\n1f, we presented 34 distinct atomic configurations of the Ru Cu (x + y = 16)\nx y\nbimetallic clusters. Following the two arrows, we started with the equilibrium\nstructures of the Ru (lower arrow) and Cu (upper arrow) clusters and gradually\n16 16\ndoped each of them with the other metal. We found that in general the formation\nenergies first decreased and then increased. The lowest formation energy was found in\nRu Cu in the upper arrow (ΔE = −8.25 eV as highlighted by red). In the red dashed\n6 10 f\nbox, we presented different structural isomers with Ru:Cu = 3:5 by varying atomic\narrangements. The variation of the formation energy for the isomers arose from\ndifferences in coordination environments and local atomic packing. In general, we\nfound that the isomers had lower formation energies with atoms that were mixed more\nuniformly, or in other words, with more Ru−Cu bonds formed.\n“12. Is there any signal of Cu2+ can be observed at higher binding energy range\nduring the in situ XPS progress?”\nWe sincerely thank the Reviewer for raising the critical question regarding whether O\n2\ninduces over-oxidation of Cu2+ during the reaction process. To rigorously verify this\npoint, we prepared a standardized compound CeO /CuO with well-defined Cu2+\n2\nvalence state as reference (ACS Energy Lett., 2021, 6, 893–899), and specifically\nsupplemented the fine Cu 2p XPS spectra of Ru Cu /CeO catalyst in the high\n0.6 1 2\nbinding energy region (~930–958 eV), where characteristic satellite peaks served as\nkey fingerprints for identifying Cu2+ (Supplementary Fig. 36). Analysis demonstrated\nthat:\n1. Reference sample CeO /CuO clearly showed strong satellite peaks near ~944 eV,\n2\nexplicitly confirming the existence of Cu2+;\n2. In sharp contrast, the corresponding spectra of Ru Cu /CeO catalyst\n0.6 1 2\nthroughout the entire reaction time window (0 to 120 min) always showed no\nobservable distinct satellite peak features;\n3. Additionally, the main peak binding energy position of Cu in Ru Cu /CeO\n0.6 1 2\nexhibited significant differences from the Cu2+ main peak in the reference sample,\nmore closely resembling characteristic values of Cu0/Cu1+.\nComprehensively considering the absence of satellite peaks, significant shift of\nmain peak binding energy position, and monitoring results across the full reaction\ntime series, we confirmed that no Cu2+ species was generated during the oxidation\nprocess on Ru Cu /CeO catalyst, thus eliminating the possibility of O causing\n0.6 1 2 2\nover-oxidation of Cu to Cu2+. These results have been incorporated into the revised\nmanuscript and are also attached below, with new content highlighted in yellow.\nSupplementary Fig. 36 | Cu 2p quasi in situ XPS spectra of CeO /CuO and\n0.6 1 2\nThe valence state of the Cu active sites was monitored using in situ X-ray\nphotoelectron spectroscopy (XPS). During the initial reaction phase under\nconcentrated solar irradiation (0–15 min), the Cu LMM Auger spectra exhibited only\nthe characteristic peaks of metallic Cu (Cu0; 918.6–919.4 eV). At 30 min, Cu1+\nspecies emerged (913.4–913.9 eV), and their relative abundance progressively\nincreased to 58% as the reaction proceeded further (Fig. 3f)23. No Cu2+ species were\ndetected in the higher binding energy range during the quasi in situ XPS analysis\n(Supplementary Fig. 36)…\nPreparation of catalysts CuO/CeO\n2\nmethod followed by calcination. Specifically, 1.5 mmol of Cu(NO ) ·3H O and 1.0\n3 2 2\nmmol of Ce(NO ) ·6H O were dissolved in 40 mL of an aqueous solution containing\n3 3 2\n2.3 M glycerol with vigorous stirring at room temperature. The resulting solution was\ntransferred to a Teflon-lined stainless-steel autoclave and hydrothermally treated at\n180 °C for 6 h. After cooling to ambient temperature, the solid product was recovered\nby centrifugation and washed repeatedly with absolute ethanol (≥3 times). The\nprecipitate was dried at 80 °C for 12 h under vacuum. The dried precursor was then\ncalcined in static air using a muffle furnace. The temperature was ramped to 350 °C at\n5 °C·min−1 and held for 2 h, yielding the final CuO/CeO catalyst.\n2\n“13. As the dissociation of H O for the proton providing, is there any H detected?”\n2 2\nWe sincerely appreciate this insightful comment regarding potential hydrogen\nevolution in our photothermal CO\n2\nanalysis in the original manuscript and provide the following clarifications supported\nby supplementary data and mechanistic analysis:\n1. Suppression of HER in Favor of CO RR:\nwere significantly suppressed due to competitive utilization of photogenerated\nelectrons. The catalyst surface preferentially adsorbed and stabilized CO reduction\n2\nintermediates, thereby steering electron flux toward CO RR pathways and effectively\n2\nsuppressing HER.\n2. Quantitative Evidence of HER Suppression:\nH was not detected in concentrated solar irradiation experiment (Supplementary Fig.\n2\n29). Quantitative electron selectivity analysis (Nat. Catal., 2025, 8, 728–739; Nat.\nCommun., 2025, 16, 6500; ACS. Catal., 2025, 15, 1–13), accounting for the electrons\nrequired per product molecule (H : 2e⁻, CO: 2e⁻, CH : 8e⁻, C H : 12e⁻), demonstrated\n2 4 2 4\nstrong preference for CO RR:\n2\n2×𝑛(𝐻 )\n𝑆𝑒𝑙 (𝐻 )=( 2 )×100%=0%\n𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛 2 2×𝑛(𝐻 )+2×𝑛(𝐶𝑂)+8×𝑛(𝐶𝐻 )+ 12×𝑛(𝐶 𝐻 )\n2 4 2 4\n2×𝑛(𝐶𝑂)\n𝑆𝑒𝑙 (𝐶𝑂)=( )×100%=4.2%\n𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛 2×𝑛(𝐻 )+2×𝑛(𝐶𝑂)+8×𝑛(𝐶𝐻 )+ 12×𝑛(𝐶 𝐻 )\n2 4 2 4\n8×𝑛(𝐶𝐻 )\n𝑆𝑒𝑙 (𝐶𝐻 )=( 4 )×100%=4.4%\n𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛 4 2×𝑛(𝐻 )+2×𝑛(𝐶𝑂)+8×𝑛(𝐶𝐻 )+ 12×𝑛(𝐶 𝐻 )\n2 4 2 4\n12×𝑛(𝐶 𝐻 )\n𝑆𝑒𝑙 (𝐶 𝐻 )=( 2 4 )×100%=91.4%\n𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛 2 4 2×𝑛(𝐻 )+2×𝑛(𝐶𝑂)+8×𝑛(𝐶𝐻 )+ 12×𝑛(𝐶 𝐻 )\n2 4 2 4\nWhere n represents the molar yield of each product.\nThe 0% electron selectivity towards H evolution, coupled with the absence of\n2\ndetectable H , provided definitive evidence for effective HER suppression. This\n2\nunequivocally underscored the catalyst’s inherent selectivity for the CO RR. The\n2\nrevised manuscript and Supplementary Information now include additional content,\nwhich is distinguished by a yellow background.\nSupplementary Fig. 29 | Time-resolved raw gas-phase signals for O and H O\n2 2\nevolution during catalytic reaction (sampling intervals: 0, 25, 30, 60, 120 min) and\nMS spectra of O obtained by photocatalytic conversion of CO and H O18 over\n2 2 2\nRu Cu (Cu0–Cu1+)/CeO with simulated sunlight irradiation for 2 h.\n0.6 1 2\nSupplementary Discussion: GC continuous monitoring was employed to investigate\nthe dynamic evolution of H O and O in the reaction system. At the initial stage of the\n2 2\nreaction (t = 0 min), only the characteristic peak of H O was detected, with a retention\n2\ntime of 4.585 min. As the reaction progressed to 25 min, a distinct O signal emerged\n2\nat 1.588 min retention time, indicative of successful initiation of oxidative processes.\nProlonged reaction duration (120 min) demonstrated continuous accumulation of O\n2\nas the oxidation product, along with a gradual decrease of H O concentration due to\n2\nreaction consumption.\n…Notably, this corresponds to a significant enhancement in C H selectivity from 0%\n2 4\nto 74.3% compared with that under non-concentrated solar irradiation, with electron\nselectivity reaching 91.4%...\nMethods\nElectron selectivity calculation\nElectron selectivity was calculated based on the consumption of 2, 2, 8 and 12\nelectrons per H , CO, CH and C H molecule, respectively, according to the\n2 4 2 4\nfollowing formulas42:\n2×𝑛(𝐻 )\n𝑆𝑒𝑙 (𝐻 )=( 2 )×100% (5)\n𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛 2 2×𝑛(𝐻 )+2×𝑛(𝐶𝑂)+8×𝑛(𝐶𝐻 )+ 12×𝑛(𝐶 𝐻 )\n2 4 2 4\n2×𝑛(𝐶𝑂)\n𝑆𝑒𝑙 (𝐶𝑂)=( )×100% (6)\n𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛 2×𝑛(𝐻 )+2×𝑛(𝐶𝑂)+8×𝑛(𝐶𝐻 )+ 12×𝑛(𝐶 𝐻 )\n2 4 2 4\n8×𝑛(𝐶𝐻 )\n𝑆𝑒𝑙 (𝐶𝐻 )=( 4 )×100% (7)\n𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛 4 2×𝑛(𝐻 )+2×𝑛(𝐶𝑂)+8×𝑛(𝐶𝐻 )+ 12×𝑛(𝐶 𝐻 )\n2 4 2 4\n12×𝑛(𝐶 𝐻 )\n𝑆𝑒𝑙 (𝐶 𝐻 )=( 2 4 )×100% (8)\n𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛 2 4 2×𝑛(𝐻 )+2×𝑛(𝐶𝑂)+8×𝑛(𝐶𝐻 )+ 12×𝑛(𝐶 𝐻 )\n2 4 2 4\nWhere n represents the molar yield of each product.\nReferences\nfor selective CO -to-C H photoreduction. Nat. Catal. 8, 728−739 (2025).\n2 2 4\n“14. What’s the specific band structure of catalysts in this work?”\nWe sincerely thank the Reviewer for this valuable comments. To thoroughly elucidate\nthe electronic band structure characteristics of the catalysts, we systematically added\nenergy level diagrams for each catalyst (Supplementary Figs. 21 and 22). This\nanalysis combined ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS)\nand XPS valence band spectra: First, absorption edges were derived from Kubelka-\nMunk-transformed UV-Vis DRS data, and optical band gaps (E ) were calculated\ng\nusing Tauc plots (Nat. Commun., 2025, 16, 6586; Adv. Energy Mater., 2025, 15,\n2404621; Adv. Mater., 2025, 37, 2416210). Second, valence band maximum (VBM)\npositions were measured directly from XPS valence band spectra. Finally, conduction\nband minimum (CBM) positions were determined by subtracting VBM from E\ng\nvalues. The measured parameters (VBM, CBM, E\ng\n) confirmed that across the catalyst\nseries, all CBMs were more negative than the thermodynamic potential for CO\n2\nreduction to target products, while all VBMs were more positive than the H O\n2\noxidation potential. This demonstrated that these catalysts could thermodynamically\ndrive both CO reduction and H O oxidation simultaneously, accounting for their high\n2 2\nphotothermal catalytic CO reduction activity. The revised manuscript and\na yellow background.\nSupplementary Fig. 21 | a-e XPS valence spectra of the CeO (a), Ru /CeO (b),\n2 0.6 2\nCu /CeO (c), Ru Cu /CeO (d) and Ru Cu (Cu0–Cu1+)/CeO catalysts (e). f-j The\n1 2 0.6 1 2 0.6 1 2\nTauc plots of CeO (f), Ru /CeO (g), Cu /CeO (h), Ru Cu /CeO (i) and\n2 0.6 2 1 2 0.6 1 2\nRu Cu (Cu0–Cu1+)/CeO catalysts (j).\n0.6 1 2\nSupplementary Fig. 22 | Energy level diagram for the CeO\n2\n, Ru\n0.6\n/CeO\n2\n, Cu\n1\n/CeO\n2\n,\nRu Cu /CeO and Ru Cu (Cu0–Cu1+)/CeO catalysts.\n0.6 1 2 0.6 1 2\n…The critical design parameters of the CeO -based and single-metal catalysts were\n2\noptimized (Supplementary Figs. 17 and 18). Additionally, the catalyst surface\ntemperatures and UV-vis diffuse reflectance spectra were obtained (Supplementary\nFigs. 19 and 20). Electronic band structure analyses demonstrated that all catalysts\ncan match the thermodynamic potentials for CO reduction and H O oxidation\n2 2\nreactions (Supplementary Figs. 21 and 22)…\n“15. What’s the condition for TGA measurement in Figure s25?”\nWe sincerely thank the Reviewer for this pertinent comment. Tests were conducted on\na TA Instruments SDT Q600 series thermogravimetric analyzer. Approximately 5.0\nmg of sample was loaded into a standard alumina crucible. Measurements were\nperformed under a high-purity nitrogen purge gas flowing at 50 mL·min−1, using a\ndynamic heating regime: the temperature was linearly ramped from 25 °C (ambient)\nto 520 °C at 10 °C·min−1. These conditions maintained oxygen-free integrity and\nensured accurate mass-loss data acquisition (Supplementary Fig. 39). Additionally, we\nfurther evaluated the thermal stability of the Ru\n0.6\nCu\n1\n(Cu0–Cu1+)/CeO\n2\ncatalyst under\na nitrogen atmosphere using differential scanning calorimetry, heating from ambient\ntemperature to 500 °C at 10 °C·min−1. No discernible endothermic or exothermic\npeaks were observed above 300 °C (Supplementary Fig. 40), indicating the absence of\nsignificant phase transitions, decomposition, or other thermally driven structural\nchanges. These results confirmed the catalyst’s excellent thermal stability and\nstructural integrity, demonstrating its suitability for concentrated solar irradiation\nenvironments involving intense light flux and elevated temperatures. This positioned\nthe material as a promising candidate for CO reduction. The revised manuscript and\na yellow background.\n0.6\nCu\n1\n(Cu0-Cu1+)/CeO\n2\n) \n% \n(\n s\n s\no100\ns\nl\ns\na D = 3.402%\nM\n90\n0 100 200 300 400 500\nTemperature (oC)\nSupplementary Fig. 39 | Thermogravimetric analysis curves of the Ru Cu (Cu0–\n0.6 1\nCu1+)/CeO catalyst.\nhigh-purity nitrogen purge (flow rate: 50 mL·min−1). A dynamic temperature program\nwas employed, ramping linearly from 25 °C to 520 °C at a constant heating rate of\n10 °C·min−1. This configuration strictly maintained oxygen-free conditions and\nensured artifact-free mass-loss data acquisition by preventing oxidative degradation.\n0.8\nRu\n0.6\nCu\n1\n(Cu0-Cu1+)/CeO\n2\n0.0\nT-0.8\nD\n-1.6\nSurface\nwater\n-2.4\ndesorption Decalescence\n0 100 200 300 400 500\nTemperature (oC)\nSupplementary Fig. 40 | Differential scanning calorimetry analysis curves of\nRu Cu (Cu0–Cu1+)/CeO .\n0.6 1 2\n…Furthermore, thermogravimetric analysis revealed that minimal mass loss (3.402%)\noccurred at 500 °C, which was attributed to the desorption of physically adsorbed\nH O; no bulk structural decomposition occurred (Supplementary Fig. 39). Differential\n2\nscanning calorimetry analysis showed no discernible endothermic or exothermic\npeaks above 300 °C (Supplementary Fig. 40), indicating the absence of significant\nphase transitions, decomposition, or other thermally induced structural changes.\nScanning electron microscopy confirmed that the catalyst morphology was preserved\nafter cycling, indicating that the lattice is structurally stable under high-temperature\nreaction conditions (Supplementary Fig. 41)…\n“16. What’s the behavior of O after activated the Cu species, adsorbed on the Ru-Cu\n2\ninterface and occupied some Ru-Cu sites?”\nWe sincerely thank the Reviewer for this insightful question regarding the behavior of\nO in the Ru–Cu cluster system. Our comprehensive study demonstrated that upon\n2\nadsorption at the Ru–Cu interface, O extracted electrons from the Ru–Cu cluster\n2\n(Bader charge analysis revealed ΔQ ≈ + 1.95e), oxidizing Cu atoms from Cu0 to Cu1+\nwhile forming stable bonds with Cu, as thoroughly analyzed in our manuscript. The\noxygen atoms exhibited remarkable thermodynamic stability, with DFT calculations\nconfirming an extremely low adsorption energy of –4.33 eV. Additionally, the\ncatalytic reaction occurred exclusively at the surface Cu0/Cu1+ sites, while the oxygen\nspecies remained chemically inert due to their strong bonding with Cu. These findings\nindicated that O served solely to oxidize Cu and stabilize the Ru–Cu cluster structure\n2\nwithout participating in subsequent catalytic processes. The oxygen species\nmaintained their initial configuration throughout the reaction cycle, functioning as\nstructural stabilizers rather than active participants in the CO reduction mechanism.\n“1. In this work, the authors develop an oxygen-mediated dynamic interfacial\nreconstruction strategy to fabricate Ru Cu (Cu0–Cu1+)/CeO catalysts with adaptive\n0.6 1 2\noxygen tolerance. This approach simultaneously addresses two critical bottlenecks in\nartificial photosynthesis for CO -to-hydrocarbon conversion: catalyst poisoning\n2\nunder high oxygen partial pressures and sluggish C -product formation kinetics.\nThe\n2\natomic-scale design features Ru single atoms occupying Ce lattice sites, forming\ndistorted pentahedral coordination fields that facilitate proton-coupled electron\ntransfer and accelerate H O dissociation. Meanwhile, concentrated solar irradiation\n2\ninduced photothermal effects drive the self-assembly of Cu0–Cu1+ charge-gradient\ninterfaces within Ru/Cu alloy clusters. This interfacial reconstruction optimizes\n*CHOCO intermediate adsorption behavior and restructures the C–C coupling\npathway. These synergistic mechanisms collectively enable superior performance:\n549 ± 20 μmol·g–1 ethylene production (74.3% selectivity) with 0.5% solar-to-\nchemical energy conversion efficiency. This work delivers compelling mechanistic\ninsights into experimental phenomena through comprehensive catalyst\ncharacterization, experimental validation, and theoretical calculations. The study is\nrecommended for publication in Nature Communications provided that the following\npoints are addressed to further enhance the clarity and precision.”\nWe sincerely thank the Reviewer for the overall positive assessment of our work and\nvaluable suggestions. To clarify the unique synergistic photothermal coupling effect,\nwe performed wavelength-dependent experiments (325 nm and 808 nm), confirming\nthe critical role of this mechanism in our thermally assisted photocatalytic system. To\nelucidate the mediating role of reaction byproduct O —derived from H O oxidation\n2 2\n(2H O → O + 4H+ + 4e⁻)—in dynamically constructing the Cu0–Cu1+ active\n2 2\ninterface, we conducted systematic H O concentration-dependent experiments. Given\n2\nthe specialized operating conditions of concentrated photothermal systems, we further\nevaluated the retained thermal stability of the Ru Cu (Cu0–Cu1+)/CeO catalyst\n0.6 1 2\nunder thermal cycling using supplementary differential scanning calorimetry. For key\nevidence regarding H O activation and hydrogen transfer processes, we provided\n2\nadditional operando DRIFTS data focused on critical spectral regions. This analysis\nsuccessfully identified evolving H O adsorbates and key hydrogen-containing\n2\nintermediates during the reaction, thereby validating the proposed reaction pathway.\nWe have diligently addressed each of these comments in a point-by-point manner and\nhave incorporated additional contents into the revised manuscript and corresponding\nSupplementary Information.\n“2. To emphasize the unique synergistic effects of photothermal coupling in this\n“thermally assisted photocatalytic system”, we recommend supplementing the study\nwith wavelength-dependent experiments (e.g., 325 nm, 808 nm) to validate the\ndistinctive role of the coupled photothermal mechanism.”\nWe sincerely thank the Reviewer for this valuable comment. The structural evolution\nof the Ru Cu (Cu0–Cu1+)/CeO catalyst was triggered by intense oxygen release\n0.6 1 2\nduring water dissociation, driven by a strong photothermal coupling effect under\nconcentrated solar irradiation. This in situ dynamic reconstruction—concurrent with\nthe oxygen evolution reaction (OER)—required OER kinetics powered by\nphotothermal synergy. Therefore, when evaluating photocatalytic performance under\nspectrally segmented light (e.g., isolated 320-nm UV irradiation or simulated 808-nm\nNIR thermal effects), the catalyst had to undergo pre-reconstruction under full-\nspectrum solar irradiation. The fundamental limitation stemmed from the inability of\nisolated UV irradiation (320 nm) or pure thermal input (808-nm simulation) alone to\nprovide sufficient driving force for oxygen evolution. Inadequate oxygen release thus\nprevented the catalyst from achieving the critical structural transformation needed to\nform the targeted highly active phase.\nBased on this understanding, we evaluated the performance of the pre-\nreconstructed catalyst (achieved via full-spectrum irradiation) by isolating specific\n320-nm (UV) and 808-nm (NIR) spectral bands. This approach enabled quantitative\ndeconvolution of the distinct contributions from light, heat, and their synergistic\neffects on catalysis. Experimental results demonstrated substantially lower catalyst\nactivity under high-flux single-band irradiation—in either UV or NIR-simulated\nthermal conditions—compared to full-spectrum illumination (Supplementary Fig. 32).\nThis performance gap was particularly pronounced for critical C–C coupling reactions.\nThe significant disparity confirmed unequivocally that photothermal synergy under\nconcentrated solar irradiation was indispensable for driving efficient C–C coupling.\nThese results have been incorporated into the revised manuscript and are also attached\nbelow, with new content highlighted in yellow.\n300\n325 nm irradiation-Ru Cu /CeO (A)\n0.6 1 2\n250 808 nm irradiation-Ru Cu /CeO (B)\n- - 1 1 · ) h ol· g\n1\n2\n5\n0\n0\n0 3\nF\n8 2 0\nu\n5 8\nll -\nn n\ns\nm m\npe\ni i\nc\nr r r\nt\nr\nr\na a\nu\nd d\nm\ni i a a t t\ni\ni i\nr\no o\nra\nn n\nd\n- - R R\nia\nu u\nt\n0 0 0\nio\n. . . 6 6 6\nn\nC C\n-\nu u\nR\n1 1 1\nu\n( ( C C u u\nC\n0 0 - -\nu\n(C\n1 1 + +\nu\n) ) / /\n-C\ne e\nu\nO O\n1\n2 2\n+\n( (\n)\nC D\n/C\n) )\neO (E)\nm 0.6 1 2\n(\ne\nμ\n4\nat\nR\n0\n(A) (B) (C) (D) (E)\nSupplementary Fig. 32 | CO reduction performance under monochromatic\n2\nirradiation.\nSupplementary Discussion: The structural evolution of the Ru Cu (Cu0–\n0.6 1\nCu1+)/CeO catalyst is triggered by intense oxygen release during water dissociation,\n2\ndriven by a strong photothermal coupling effect under concentrated solar irradiation.\nThis in situ dynamic reconstruction—concurrent with the OER—requires OER\nkinetics powered by photothermal synergy. Therefore, when evaluating photocatalytic\nperformance under spectrally segmented light (e.g., isolated 320-nm UV irradiation or\nsimulated 808-nm NIR thermal effects), the catalyst had to undergo pre-reconstruction\nunder full-spectrum solar irradiation. The fundamental limitation stems from the\ninability of isolated UV irradiation (320 nm) or pure thermal input (808-nm\nsimulation) alone to provide sufficient driving force for oxygen evolution. Inadequate\noxygen release thus prevents the catalyst from achieving the critical structural\ntransformation needed to form the targeted highly active phase.\n…(2) Maintaining temperature at 462 °C while irradiating with lower-intensity UV\nlight (50–250 mW·cm−2) also yielded no C H (Supplementary Fig. 30). Control\n2 4\nexperiments—including systems without H O, CO , or catalytic components—\n2 2\nsimilarly demonstrated no C H signals. Furthermore, the catalytic system can be\n2 4\ndefined as a thermally assisted photocatalytic system (Supplementary Figs. 31 and\n32)…\n“3. The reaction-generated O byproduct critically mediates the in situ dynamic\n2\nreconstruction of Cu0–Cu+ active interfaces. The proposed mechanism explicitly\nindicates that this O primarily originates from the oxidation of H O molecules (2H O\n2 2 2\n→ O + 4H+ + 4e⁻). We recommend that the authors supplement this study with\n2\nsystematic H O concentration-dependent experiments.”\nclarify the critical role of O in forming the Cu0–Cu1+ active interface and enhancing\n2 2 2\n→ O + 4H+ + 4e⁻)—we systematically performed concentrated solar-driven CO\n2 2\nreduction experiments over a gradient of water volumes (0.5, 1.0, 1.5, 2.0, 2.5 mL).\nResults demonstrated a pronounced correlation between C\n4\nyield and H\nconcentration (Supplementary Fig. 16).\nBelow 1.0 mL H O, C H yield remained low. This was due to: (1) insufficient\n2 2 4\nactivation of H\nreduction; and (2) critically, low O generation rates, which slowed the in situ\n2\ndynamic reconstruction of the Cu0–Cu1+ interface, thereby impairing C–C coupling.\nC H yield peaked at 1.0 mL H O. This optimal concentration ensured adequate *H\n2 4 2\nsupply and sufficient O generation to maintain the Cu0–Cu1+ interface for efficient\n4\nyield progressively\ndeclined. This reduction stemmed from: (1) excess H O favoring the competitive\n2\nhydrogen evolution reaction (HER: 2H+ + 2e⁻ → H ), which consumed electrons and\n2\nprotons otherwise available for CO reduction; and (2) saturation of active sites on the\n2\ncatalyst surface. Notably, at volumes ≥2.0 mL, the decline moderated, indicating\nsaturation of surface sites capable of utilizing H O to generate O and reconstruct the\n2 2\nactive interface. Excess H O cannot be effectively activated to promote the target\n2\nreaction, thus stabilizing C H yield at a lower-level plateau.\n2 4\nCollectively, these experiments demonstrated that: (1) O generation was essential\n2\nto activate and dynamically reconstruct the Cu0–Cu1+ interface, enabling efficient C–\nC coupling; and (2) O generation rates—governed by H O concentration—had to be\n2 2\noptimized, as both deficient and excessive H O suppressed target product formation.\nbelow, with new content highlighted in yellow.\nSupplementary Fig. 16 | CO reduction performance with varying H O addition.\n2 2\nSupplementary Discussion: Below 1.0 mL H\n4\nyield remained low due to: (1)\ninsufficient H O activation, limiting the supply of reactive adsorbed hydrogen (*H) for\n2\nreduction; and critically, (2) low O generation rates, impeding the in situ dynamic\n2\nreconstruction of the essential Cu0–Cu1+ interface required for efficient C–C coupling.\nThe C H yield peaked at 1.0 mL H O, where optimal H O concentration ensures\n2 4 2 2\nadequate *H supply and sufficient O generation to maintain the active Cu0–Cu1+\n2\ninterface for coupling. At higher H O volumes (≥1.5 mL), C H yield progressively\n2 2 4\ndeclined, primarily due to: (1) enhanced competition from the hydrogen evolution\nreaction (HER: 2H+ + 2e⁻ → H ); and (2) saturation of active surface sites. Notably,\n2\nthe decline moderated at volumes ≥2.0 mL, indicating saturation of sites capable of\nutilizing H O for O generation and interfacial reconstruction. Excess H O cannot be\n2 2 2\neffectively activated for the target reaction, resulting in a stabilized, lower-yield\nplateau.\nTo enhance the direct solar-to-chemical energy conversion efficiency, we performed\nexperiments under concentrated solar irradiation (5000 mW·cm−2) with the aim of\nincreasing high-energy electron transfers and localized thermal effects by harnessing\nsolar-induced photon–phonon coupling (Supplementary Fig. 15). We systematically\noptimized H O concentration to maximize performance (Supplementary Fig. 16). The\n2\ncritical design parameters of the CeO -based and single-metal catalysts were\n2\noptimized (Supplementary Figs. 17 and 18)…\n“4. Given the unique operating environment of concentrated solar photothermal\ncatalysis systems, evaluating the Ru Cu (Cu0–Cu1+)/CeO catalyst's tolerance to\n0.6 1 2\nthermal-induced deactivation is imperative. We recommend supplementing this study\nwith differential scanning calorimetry data for the catalyst.”\nWe sincerely thank the Reviewer for this pertinent comment. The thermal stability of\nthe Ru\n0.6\nCu\n1\n(Cu0–Cu1+)/CeO\n2\ncatalyst was evaluated under a nitrogen atmosphere\nusing differential scanning calorimetry, heating from ambient temperature to 500 °C\nat 10 °C·min⁻1. No discernible endothermic or exothermic events were observed\nabove 300 °C (Supplementary Fig. 40), indicating the absence of significant phase\ntransitions, decomposition, or other thermally driven structural changes. These results\nconfirmed the catalyst’s excellent thermal stability and structural integrity,\ndemonstrating its suitability for concentrated solar irradiation environments involved\nintense light flux and elevated temperatures. This positioned the material as a\npromising candidate for CO reduction. These results have been incorporated into the\n2\nrevised manuscript and are also attached below, with new content highlighted in\nyellow.\n0.8\nRu\n0.6\nCu\n1\n(Cu0-Cu1+)/CeO\n2\n0.0\nT-0.8\nD\n-1.6\nSurface\nwater\n-2.4\ndesorption Decalescence\n0 100 200 300 400 500\nTemperature (oC)\nSupplementary Fig. 40 | Differential scanning calorimetry analysis curves of\nRu Cu (Cu0–Cu1+)/CeO .\n0.6 1 2\n…Furthermore, thermogravimetric analysis revealed that minimal mass loss (3.402%)\noccurred at 500 °C, which was attributed to the desorption of physically adsorbed\nH O; no bulk structural decomposition occurred (Supplementary Fig. 39). Differential\n2\nscanning calorimetry analysis showed no discernible endothermic or exothermic\npeaks above 300 °C (Supplementary Fig. 40), indicating the absence of significant\nphase transitions, decomposition, or other thermally induced structural changes.\nScanning electron microscopy confirmed that the catalyst morphology was preserved\nafter cycling, indicating that the lattice is structurally stable under high-temperature\nreaction conditions (Supplementary Fig. 41)…\n“5. The in-situ DRIFTS data presented in Figure 4e provide critical evidence for\ntracking the dynamic evolution of key carbon-based intermediates along the C H\n2 4\nformation pathway. The study explicitly identifies H O as both the reaction medium\n2\nand the crucial hydrogen source. However, the current spectral analysis primarily\nfocuses on carbon species evolution and does not directly capture concurrent\nspectroscopic evidence for H O molecule activation or hydrogen transfer processes. It\n2\nis strongly recommended that the authors supplement their analysis by presenting the\nrelevant spectral regions associated with H O evolution and critical hydrogen-\n2\ncontaining intermediates from the in-situ DRIFTS data.”\nWe sincerely thank the Reviewer for this pertinent comment. Under concentrated\nsolar irradiation (AM 1.5G, 5000 mW·cm⁻2), Operando DRIFTS analysis of\nCO /H O co-adsorption revealed in situ formation of intermediates during 120 min\n2 2\nillumination. The Ru Cu /CeO catalyst surface showed characteristic vibrational\n0.6 1 2\nmodes for surface-bound *OH radicals (3568, 3627, and 3648 cm⁻1) and dissociative\nH O adsorption via ʋ(O–H) stretches (3670, 3701, and 3734 cm⁻1; Supplementary Fig.\n2\n49) (Nat. Commun., 2024, 15, 4675; Nano energy, 2023, 113, 108578; Angew. Chem.\nInt. Ed., 2024, 63, e202410474). These signatures confirmed hole-mediated H O\n2\ndissociation pathway that supplies protons for CO\n2\nreduction. This evidence validated\nthe kinetic relevance of the four-step H O oxidation mechanism, as captured through\n2\nthe observed intermediates (Supplementary Fig. 50). As shown:\n(1) H O + * + h+ → *OH + H+\n2\n(2) *OH + h+ → *O + H+\n(3) *O + H O + h+ → *OOH + H+\n2\n(4) *OOH + h+ → O + H+ + *\n2\n* represents the active site.\nThese results have been incorporated into the revised manuscript and are also\nattached below, with new content highlighted in yellow.\nSupplementary Fig. 49 | Operando DRIFTS of H O activation intermediates on\n0.6 1 2\nThe reaction cascade occurs through four concerted steps:\n1. H O adsorption and oxidation:\n2\nhydroxyl species (*OH) while releasing a proton (H+).\n2. Hydroxyl oxidation:\n*OH + h⁺ → *O + H+\nSubsequent hole oxidation deprotonates *OH, yielding adsorbed atomic oxygen (*O)\nand a H+.\n3. O–O bond formation:\n*O + H O + h⁺ → *OOH + H+\n2\nadsorbate (*OOH), releasing a third H+.\n4. O liberation:\n2\n*OOH + h⁺ → O + H+ + *\n2 2\n…This strict temporal coupling between the formation of C–C coupling intermediates\nand interfacial reconstruction demonstrates that the O -mediated dynamic interfacial\n2\nrestructuring effectively reduces the energy barrier for C–C coupling, thereby\nenabling precise regulation of the C H synthesis pathway. Furthermore, the\n2 4\nRu Cu /CeO catalyst surface showed characteristic vibrational modes for surface-\n0.6 1 2\nbound *OH radicals (3568, 3627, and 3648 cm⁻1) and dissociative H O adsorption via\n2\nʋ(O–H) stretches (3670, 3701, and 3734 cm⁻1; Supplementary Fig. 49). These\nsignatures confirm hole-mediated H O dissociation pathway that supplies protons for\nReviewer #1:\n“1. I thank the authors for having carefully considered my previous points. I am now\nsatisfied with much of their work, however I would like them to tackle two remaining\nopen comments.”\nWe sincerely appreciate the Reviewer’s constructive appraisal of our work and their\nincisive commentary. In response to Comment 1, we rigorously recalibrated formation\nenergies for all 34 cluster configurations, consolidating this study’s thermodynamic\nfoundation. Regarding Comment 2, we excluded the contested high-temperature\nmolecular dynamics data due to methodological concerns and replaced this section\nwith first-principles calculations of site-specific adsorption energetics.\nComplementing these analyses, we integrated quasi in situ XPS evidence tracking\ndynamic copper valence evolution, which unambiguously validates the proposed\noxidation mechanism experimentally. We have diligently addressed each of these\ncomments in a point-by-point manner and have incorporated additional contents into\nthe revised manuscript and corresponding Supplementary Information.\n“2. I don't agree with the reference energies chosen for estimating formation energies\nof the Cu Ru clusters. I would choose the energy per atom of bulk Cu and Ru\nx y\ninstead.”\nWe sincerely appreciate the Reviewer’s insightful suggestions regarding the critical\nchoice of energy reference standards. The reason why we chose the energies of\nseparate elemental clusters as the reference energies is that in this way the negative\nformation energies of the binary clusters indicated the doped Cu and Ru preferred to\nform alloys. The more negative the formation energy was, the better stability the alloy\ncluster had. We fully agree with the Reviewer that adopting bulk metal energies as a\nreference is well-founded, particularly due to their clear physical significance in\nlattice formation energetics. We therefore acknowledge the value of bulk-phase\nreferences for elucidating material phase-separation behaviors. Following rigorous\nverification, we recalculated formation energies for all 34 Cu Ru clusters in their\nx y\nglobal minimum-energy configurations using the revised bulk energy reference.\nUnder the new definition, the updated formation energies for all the clusters are\npositive. This indicates that the doping process—where dopant atoms are moved from\ntheir bulk phases to the surface of CeO —is an endothermic process, which is\n2\nreasonable. Critically, Ru Cu consistently exhibits the lowest formation energy—\n3 5\nsignificantly lower than all other compositions. This confirms, with enhanced\nthermodynamic precision, that Ru Cu constitutes the most stable cluster in this\n3 5\nsystem. The revised manuscript and Supplementary Information now include\nadditional content, which is distinguished by a yellow background.\nFig. 1 | Mechanistic evolution in multiscale metal-site catalysis. a-c, Advantages of\nM (a), M (b), and M + M (c) configurations. d, Tackling the catalytic challenges\n1 n 1 n\nposed by sub-nanoscale metal sites. e, Innovative in situ dynamic modulation of sub-\nnanoscale metal sites in this work. Effective modulation of valence states i), and\nelectronic structures ii) of sub-nanoscale metal sites, thereby breaking the activity-\nselectivity-stability trade-off in C–C coupling iii). f, DFT derived formation energy\nprofiles for 34 distinct Ru-Cu bimetallic configurations, with atomic color-coding\nreflecting elemental composition (Cu: purple; Ru: silver).\n…A total of 34 supercell models with distinct stoichiometric ratios were constructed\n(Fig. 1f). Among these, the Ru Cu configuration exhibited the lowest formation\n3 5\nenergy (0.76 eV). The formation energies of alloy clusters with other atomic\nproportions gradually increased as the Ru or Cu content increased, confirming the\nintrinsic stability of Ru Cu as a thermodynamic ground-state structure…\n3 5\nDFT-based computational framework for surface adsorption energetics and\nreaction thermodynamics\nAll first principles calculations were carried out within the framework of DFT as\nimplemented in Vienna ab initio simulation package (VASP)43,44. Periodic boundary\nconditions were applied to simulate the surfaces of the two-dimensional slabs, with a\nvacuum spacing of 20 Å. The reciprocal space was sampled by a fine grid of 3 × 3 × 1\nk-points in the Brillouin zone45. We used projector-augmented-wave (PAW)\npseudopotentials and the Perdew-Burke-Ernzerhof (PBE) exchange-correlation\napproximation46-48. Electronic wave function was expanded on a plane wave basis set\nwith the cutoff energy of 500 eV. A total energy difference between subsequent self-\nconsistency iterations below 10−5 eV was used as the criterion for reaching self-\nconsistency. All geometries were optimized using the conjugate-gradient method49,\nuntil none of the residual Hellmann-Feynman forces exceeded 10−2 eV/Å.\nGibbs free energy change (𝐺) of each chemical reaction step was calculated by:\n𝐺 = 𝐸 +𝐸 −𝑇𝑆 (9)\n𝐷𝐹𝑇 𝑍𝑃𝐸\nwhere 𝐸 , 𝐸 , 𝑇, and 𝑆 denote total energy obtained from DFT, zero-point\n𝐷𝐹𝑇 𝑍𝑃𝐸\nenergy, temperature, and entropy, respectively. The temperature was set as room\ntemperature, i.e. 298.15 K. The zero-point energy and entropy were calculated in\nVASPKIT code48. Adsorption energy ∆𝐸 on the surface of substrates was defined\n𝑎𝑑\nas:\n∆𝐸 = 𝐸 −(𝐸 +𝐸 ) (10)\n𝑎𝑑 ∗𝑚𝑜𝑙𝑒 ∗ 𝑚𝑜𝑙𝑒\nwhere 𝐸 , 𝐸 , and 𝐸 denote energies of the adsorbed molecule on substrates,\n∗𝑚𝑜𝑙𝑒 ∗ 𝑚𝑜𝑙𝑒\nthe bare substrates, and the molecule.\nThe formation energy (E) is defined as:\nf\n𝐸 = 𝐸(𝐴 𝐵 )−𝑥𝐸 −𝑦𝐸 (11)\n𝑓 𝑥 𝑦 𝐴 𝐵\nwhere 𝐸(𝐴 𝐵 ) refers to the energy of the 𝐴 𝐵 clusters. E and E refer the energy\n𝑥 𝑦 𝑥 𝑦 𝐴 B\nper atom of A bulk and B bulk, respectively. The smaller the formation energy, the\neasier it is to form, and the more stable the structure.\nReferences\namorphous-semiconductor transition in germanium. Phys. Rev. B 49, 14251 (1994).\nB 13, 5188 (1976).\nmethod. Phys. Rev. B 59, 1758 (1999).\nLett. 77, 3865 (1996).\nRev. B 40, 12255−12263 (1989).\ndimensional materials for photocatalytic water splitting. J. Phys. Chem. C 121,\n7615−7624 (2017).\n“3. I am still skeptical of the choice of running high temperature molecular dynamics,\nat a reaction temperature which is beyond the liquid/gas transition of water. Do the\nauthors imply that the H O molecules which enable the formation of oxidized Cu are\n2\nin gas phase then?”\nWe sincerely appreciate the Reviewer’s valuable insights, which are essential to\nenhancing our work. Regarding the concerns about water’s phase behavior in\nmolecular dynamics simulations at high temperatures, we fully acknowledge the\nreviewer’s reservations about the state of water above the vapour–liquid transition\npoint (~100 °C). In our initial response to Reviewers (R1), we explained the inherent\nfinite-size effects and periodic boundary conditions (PBCs). Even our smallest test\nsystem—a single isolated H O molecule—exhibits an effective density of ~2.069 ×\n2\n106 g/m3 under PBCs. This contrasts starkly with authentic vapour-phase densities\n(~2.99 × 102 g/m3), demonstrating that such systems cannot reasonably represent\nvapour-phase properties under real reaction conditions.\nUpon reevaluation of the reviewer concerns regarding current methodological\nconstraints in simulating vapour-phase dynamics, we conclude that high-temperature\nmolecular dynamics simulations are unsuitable as evidence for the proposed reaction\nmechanism. Consequently, all related molecular dynamics data and mechanistic\ninterpretations have been removed from the resubmitted manuscript.\nTo gain deeper insights into active-site reactivity and assess the role of the reaction\nmedium, we employed density functional theory (DFT) to investigate the adsorption\nof key reactants (CO , H O, O ) on distinct model surfaces: a CeO substrate, isolated\n2 2 2 2\nRu single-atom sites, and RuCu alloy clusters (Supplementary Figs. 43 and 44). The\nRuCu alloy clusters exhibit the strongest CO adsorption energy (−0.12 eV),\n2\nexceeding those of both the CeO substrate (−0.06 eV) and Ru single-atom sites\n2\n(−0.08 eV), indicating preferential adsorption at RuCu sites. In contrast, Ru single\natom sites display strong hydrophilicity, with a significantly higher H O adsorption\n2\nenergy (−1.01 eV) than those on the CeO substrate (−0.38 eV) or RuCu alloy clusters\n2\n(−0.50 eV). Notably, RuCu alloy clusters show exceptional O adsorption strength\n2\n(−2.70 eV), substantially more favorable than adsorption on the CeO substrate (−1.13\n2\neV) or Ru single-atom sites (−1.81 eV). These adsorption trends align closely with\ntemperature-programmed desorption (TPD) results (Fig. 4a–c). The revised\nmanuscript and Supplementary Information now include additional content, which is\ndistinguished by a yellow background.\nFig. 4 | Active sites verification and operando characterization of C H -formation\n2 4\nintermediates. a, CO -TPD. b, H O-TPD. c, O -TPD.\n2 2 2\nSupplementary Fig. 43 | a-c Comparative adsorption energies of CO (a), H O (b),\n2 2\nand O (c) on different catalyst surfaces.\n2 2 2\ndifferent catalyst surfaces.\nProduct selectivity critically relies on the dynamic adsorption and directional\nactivation of reactants. DFT calculations revealed reactant adsorption dynamics on\nthree structural motifs: the CeO substrate, isolated Ru single-atom sites, and RuCu\n2\nalloy clusters (Supplementary Figs. 43 and 44). RuCu alloy clusters exhibited optimal\nCO adsorption energy (−0.12 eV), significantly higher than values for CeO (−0.06\n2 2\neV) or Ru single-atom sites (−0.08 eV). In contrast, water adsorption was strongest\non Ru single atoms (−1.01 eV), exceeding adsorption on CeO (−0.38 eV) or RuCu\n2\nclusters (−0.50 eV), confirming site-specific affinity for polar molecules. Notably,\nRuCu clusters showed the strongest O adsorption energy (−2.70 eV), approximately\n2\n1.50 eV more negative than those for CeO (−1.13 eV) and Ru single atoms (−1.81\n2\neV), demonstrating superior oxygen activation capacity. Collectively, these results\nestablish RuCu clusters as synergistic CO /O activation centers…\n2 2\nTo rigorously verify the role of H O in modulating the oxidation state of copper, we\n2\nprepared a standardized CeO /CuO compound with a well-defined Cu2+ valence state\n2\nas reference (ACS Energy Lett., 2021, 6, 893–899), and specifically supplemented the\nfine Cu 2p XPS spectra of Ru Cu /CeO catalyst in the high binding energy region\n0.6 1 2\n(~930–958 eV), where characteristic satellite peaks served as key fingerprints for\nidentifying Cu2+ (Supplementary Fig. 35). Analysis demonstrated that:\n1. Reference sample CeO /CuO clearly showed strong satellite peaks near ~944 eV,\n2\nexplicitly confirming the existence of Cu2+;\n2. In sharp contrast, the corresponding spectra of Ru Cu /CeO catalyst\n0.6 1 2\nthroughout the entire reaction time window (0 to 120 min) always showed no\nobservable distinct satellite peak features;\n3. Additionally, the main peak binding energy position of Cu in Ru Cu /CeO\n0.6 1 2\nexhibited significant differences from the Cu2+ main peak in the reference sample,\nmore closely resembling characteristic values of Cu0/Cu1+.\nComprehensively considering the absence of satellite peaks, significant shift of\nmain peak binding energy position, and monitoring results across the full reaction\ntime series, we confirmed that no Cu2+ species was generated during the oxidation\nprocess on Ru Cu /CeO catalyst, thus eliminating the possibility of O causing\n0.6 1 2 2\nover-oxidation of Cu to Cu2+. These results have been incorporated into the revised\nmanuscript and are also attached below, with new content highlighted in yellow.\nSupplementary Fig. 35 | Cu 2p quasi in situ XPS spectra of CeO /CuO and\n0.6 1 2\nThe valence state of the Cu active sites was monitored using in situ X-ray\nphotoelectron spectroscopy (XPS). During the initial reaction phase under\nconcentrated solar irradiation (0–15 min), the Cu LMM Auger spectra exhibited only\nthe characteristic peaks of metallic Cu (Cu0; 918.6–919.4 eV). At 30 min, Cu1+\nspecies emerged (913.4–913.9 eV), and their relative abundance progressively\nincreased to 58% as the reaction proceeded further (Fig. 3f)23. No Cu2+ species were\ndetected in the higher binding energy range during the quasi in situ XPS analysis\n(Supplementary Fig. 35)…\nPreparation of catalysts CuO/CeO\n2\nmethod followed by calcination. Specifically, 1.5 mmol of Cu(NO ) ·3H O and 1.0\n3 2 2\nmmol of Ce(NO ) ·6H O were dissolved in 40 mL of an aqueous solution containing\n3 3 2\n2.3 M glycerol with vigorous stirring at room temperature. The resulting solution was\ntransferred to a Teflon-lined stainless-steel autoclave and hydrothermally treated at\n180 °C for 6 h. After cooling to ambient temperature, the solid product was recovered\nby centrifugation and washed repeatedly with absolute ethanol (≥3 times). The\nprecipitate was dried at 80 °C for 12 h under vacuum. The dried precursor was then\ncalcined in static air using a muffle furnace. The temperature was ramped to 350 °C at\n5 °C·min−1 and held for 2 h, yielding the final CuO/CeO catalyst.\n“The manuscript has been improved obviously, and can be accepted now.”\nWe are grateful for the thoughtful comments and recommendations provided by this\nreviewer. Thank you for your valuable input.\nReviewer #3:\n“The authors have addressed my comments well, I therefore recommend publication\nat this stage.”\nWe are grateful for the thoughtful comments and recommendations provided by this\nreviewer. Thank you for your valuable input.\nReviewer #4:\n“The author has addressed my concerns and agrees to accept the current version.”\nWe are grateful for the thoughtful comments and recommendations provided by this\nreviewer. Thank you for your valuable input.\nPoint-by-Point Responses to Reviewers’ Comments\nReviewer #1:\n“I thank the authors for the rigorous consideration of my comments. I can now\nrecommend publication.”\nWe are grateful for the thoughtful comments and recommendations provided by this\nreviewer. Thank you for your valuable input."}, {"round": 2, "reviewer_comments": {"reviewer_1": "I thank the authors for having carefully considered my previous points. I am now satisfied with much of their work, however I would like them to tackle two remaining open comments.\n(1) I don't agree with the reference energies chosen for estimating formation energies of the CuxRuy clusters. I would choose the energy per atom of bulk Cu and Ru instead.\n(2) I am still skeptical of the choice of running high temperature molecular dynamics, at a reaction temperature which is beyond the liquid/gas transition of water. Do the authors imply that the H2O molecules which enable the formation of oxidized Cu are in gas phase then?", "reviewer_2": "the manuscript has been improved obviously, and can be accepted now.", "reviewer_3": "The authors have addressed my comments well, I therefore recommend publication at this stage.", "reviewer_4": "The author has addressed my concerns and agrees to accept the current version."}, "author_response": "Point-by-Point Responses to Reviewers’ Comments\nReviewer #1:\n“1. I thank the authors for having carefully considered my previous points. I am now\nsatisfied with much of their work, however I would like them to tackle two remaining\nopen comments.”\nWe sincerely appreciate the Reviewer’s constructive appraisal of our work and their\nincisive commentary. In response to Comment 1, we rigorously recalibrated formation\nenergies for all 34 cluster configurations, consolidating this study’s thermodynamic\nfoundation. Regarding Comment 2, we excluded the contested high-temperature\nmolecular dynamics data due to methodological concerns and replaced this section\nwith first-principles calculations of site-specific adsorption energetics.\nComplementing these analyses, we integrated quasi in situ XPS evidence tracking\ndynamic copper valence evolution, which unambiguously validates the proposed\noxidation mechanism experimentally. We have diligently addressed each of these\ncomments in a point-by-point manner and have incorporated additional contents into\nthe revised manuscript and corresponding Supplementary Information.\n“2. I don't agree with the reference energies chosen for estimating formation energies\nof the Cu Ru clusters. I would choose the energy per atom of bulk Cu and Ru\nx y\ninstead.”\nWe sincerely appreciate the Reviewer’s insightful suggestions regarding the critical\nchoice of energy reference standards. The reason why we chose the energies of\nseparate elemental clusters as the reference energies is that in this way the negative\nformation energies of the binary clusters indicated the doped Cu and Ru preferred to\nform alloys. The more negative the formation energy was, the better stability the alloy\ncluster had. We fully agree with the Reviewer that adopting bulk metal energies as a\nreference is well-founded, particularly due to their clear physical significance in\nlattice formation energetics. We therefore acknowledge the value of bulk-phase\nreferences for elucidating material phase-separation behaviors. Following rigorous\nverification, we recalculated formation energies for all 34 Cu Ru clusters in their\nx y\nglobal minimum-energy configurations using the revised bulk energy reference.\nUnder the new definition, the updated formation energies for all the clusters are\npositive. This indicates that the doping process—where dopant atoms are moved from\ntheir bulk phases to the surface of CeO —is an endothermic process, which is\n2\nreasonable. Critically, Ru Cu consistently exhibits the lowest formation energy—\n3 5\nsignificantly lower than all other compositions. This confirms, with enhanced\nthermodynamic precision, that Ru Cu constitutes the most stable cluster in this\n3 5\nsystem. The revised manuscript and Supplementary Information now include\nadditional content, which is distinguished by a yellow background.\nFig. 1 | Mechanistic evolution in multiscale metal-site catalysis. a-c, Advantages of\nM (a), M (b), and M + M (c) configurations. d, Tackling the catalytic challenges\n1 n 1 n\nposed by sub-nanoscale metal sites. e, Innovative in situ dynamic modulation of sub-\nnanoscale metal sites in this work. Effective modulation of valence states i), and\nelectronic structures ii) of sub-nanoscale metal sites, thereby breaking the activity-\nselectivity-stability trade-off in C–C coupling iii). f, DFT derived formation energy\nprofiles for 34 distinct Ru-Cu bimetallic configurations, with atomic color-coding\nreflecting elemental composition (Cu: purple; Ru: silver).\n…A total of 34 supercell models with distinct stoichiometric ratios were constructed\n(Fig. 1f). Among these, the Ru Cu configuration exhibited the lowest formation\n3 5\nenergy (0.76 eV). The formation energies of alloy clusters with other atomic\nproportions gradually increased as the Ru or Cu content increased, confirming the\nintrinsic stability of Ru Cu as a thermodynamic ground-state structure…\n3 5\nDFT-based computational framework for surface adsorption energetics and\nreaction thermodynamics\nAll first principles calculations were carried out within the framework of DFT as\nimplemented in Vienna ab initio simulation package (VASP)43,44. Periodic boundary\nconditions were applied to simulate the surfaces of the two-dimensional slabs, with a\nvacuum spacing of 20 Å. The reciprocal space was sampled by a fine grid of 3 × 3 × 1\nk-points in the Brillouin zone45. We used projector-augmented-wave (PAW)\npseudopotentials and the Perdew-Burke-Ernzerhof (PBE) exchange-correlation\napproximation46-48. Electronic wave function was expanded on a plane wave basis set\nwith the cutoff energy of 500 eV. A total energy difference between subsequent self-\nconsistency iterations below 10−5 eV was used as the criterion for reaching self-\nconsistency. All geometries were optimized using the conjugate-gradient method49,\nuntil none of the residual Hellmann-Feynman forces exceeded 10−2 eV/Å.\nGibbs free energy change (𝐺) of each chemical reaction step was calculated by:\n𝐺 = 𝐸 +𝐸 −𝑇𝑆 (9)\n𝐷𝐹𝑇 𝑍𝑃𝐸\nwhere 𝐸 , 𝐸 , 𝑇, and 𝑆 denote total energy obtained from DFT, zero-point\n𝐷𝐹𝑇 𝑍𝑃𝐸\nenergy, temperature, and entropy, respectively. The temperature was set as room\ntemperature, i.e. 298.15 K. The zero-point energy and entropy were calculated in\nVASPKIT code48. Adsorption energy ∆𝐸 on the surface of substrates was defined\n𝑎𝑑\nas:\n∆𝐸 = 𝐸 −(𝐸 +𝐸 ) (10)\n𝑎𝑑 ∗𝑚𝑜𝑙𝑒 ∗ 𝑚𝑜𝑙𝑒\nwhere 𝐸 , 𝐸 , and 𝐸 denote energies of the adsorbed molecule on substrates,\n∗𝑚𝑜𝑙𝑒 ∗ 𝑚𝑜𝑙𝑒\nthe bare substrates, and the molecule.\nThe formation energy (E) is defined as:\nf\n𝐸 = 𝐸(𝐴 𝐵 )−𝑥𝐸 −𝑦𝐸 (11)\n𝑓 𝑥 𝑦 𝐴 𝐵\nwhere 𝐸(𝐴 𝐵 ) refers to the energy of the 𝐴 𝐵 clusters. E and E refer the energy\n𝑥 𝑦 𝑥 𝑦 𝐴 B\nper atom of A bulk and B bulk, respectively. The smaller the formation energy, the\neasier it is to form, and the more stable the structure.\nReferences\namorphous-semiconductor transition in germanium. Phys. Rev. B 49, 14251 (1994).\nB 13, 5188 (1976).\nmethod. Phys. Rev. B 59, 1758 (1999).\nLett. 77, 3865 (1996).\nRev. B 40, 12255−12263 (1989).\ndimensional materials for photocatalytic water splitting. J. Phys. Chem. C 121,\n7615−7624 (2017).\n“3. I am still skeptical of the choice of running high temperature molecular dynamics,\nat a reaction temperature which is beyond the liquid/gas transition of water. Do the\nauthors imply that the H O molecules which enable the formation of oxidized Cu are\n2\nin gas phase then?”\nWe sincerely appreciate the Reviewer’s valuable insights, which are essential to\nenhancing our work. Regarding the concerns about water’s phase behavior in\nmolecular dynamics simulations at high temperatures, we fully acknowledge the\nreviewer’s reservations about the state of water above the vapour–liquid transition\npoint (~100 °C). In our initial response to Reviewers (R1), we explained the inherent\nfinite-size effects and periodic boundary conditions (PBCs). Even our smallest test\nsystem—a single isolated H O molecule—exhibits an effective density of ~2.069 ×\n2\n106 g/m3 under PBCs. This contrasts starkly with authentic vapour-phase densities\n(~2.99 × 102 g/m3), demonstrating that such systems cannot reasonably represent\nvapour-phase properties under real reaction conditions.\nUpon reevaluation of the reviewer concerns regarding current methodological\nconstraints in simulating vapour-phase dynamics, we conclude that high-temperature\nmolecular dynamics simulations are unsuitable as evidence for the proposed reaction\nmechanism. Consequently, all related molecular dynamics data and mechanistic\ninterpretations have been removed from the resubmitted manuscript.\nTo gain deeper insights into active-site reactivity and assess the role of the reaction\nmedium, we employed density functional theory (DFT) to investigate the adsorption\nof key reactants (CO , H O, O ) on distinct model surfaces: a CeO substrate, isolated\n2 2 2 2\nRu single-atom sites, and RuCu alloy clusters (Supplementary Figs. 43 and 44). The\nRuCu alloy clusters exhibit the strongest CO adsorption energy (−0.12 eV),\n2\nexceeding those of both the CeO substrate (−0.06 eV) and Ru single-atom sites\n2\n(−0.08 eV), indicating preferential adsorption at RuCu sites. In contrast, Ru single\natom sites display strong hydrophilicity, with a significantly higher H O adsorption\n2\nenergy (−1.01 eV) than those on the CeO substrate (−0.38 eV) or RuCu alloy clusters\n2\n(−0.50 eV). Notably, RuCu alloy clusters show exceptional O adsorption strength\n2\n(−2.70 eV), substantially more favorable than adsorption on the CeO substrate (−1.13\n2\neV) or Ru single-atom sites (−1.81 eV). These adsorption trends align closely with\ntemperature-programmed desorption (TPD) results (Fig. 4a–c). The revised\nmanuscript and Supplementary Information now include additional content, which is\ndistinguished by a yellow background.\nFig. 4 | Active sites verification and operando characterization of C H -formation\n2 4\nintermediates. a, CO -TPD. b, H O-TPD. c, O -TPD.\n2 2 2\nSupplementary Fig. 43 | a-c Comparative adsorption energies of CO (a), H O (b),\n2 2\nand O (c) on different catalyst surfaces.\n2 2 2\ndifferent catalyst surfaces.\nProduct selectivity critically relies on the dynamic adsorption and directional\nactivation of reactants. DFT calculations revealed reactant adsorption dynamics on\nthree structural motifs: the CeO substrate, isolated Ru single-atom sites, and RuCu\n2\nalloy clusters (Supplementary Figs. 43 and 44). RuCu alloy clusters exhibited optimal\nCO adsorption energy (−0.12 eV), significantly higher than values for CeO (−0.06\n2 2\neV) or Ru single-atom sites (−0.08 eV). In contrast, water adsorption was strongest\non Ru single atoms (−1.01 eV), exceeding adsorption on CeO (−0.38 eV) or RuCu\n2\nclusters (−0.50 eV), confirming site-specific affinity for polar molecules. Notably,\nRuCu clusters showed the strongest O adsorption energy (−2.70 eV), approximately\n2\n1.50 eV more negative than those for CeO (−1.13 eV) and Ru single atoms (−1.81\n2\neV), demonstrating superior oxygen activation capacity. Collectively, these results\nestablish RuCu clusters as synergistic CO /O activation centers…\n2 2\nTo rigorously verify the role of H O in modulating the oxidation state of copper, we\n2\nprepared a standardized CeO /CuO compound with a well-defined Cu2+ valence state\n2\nas reference (ACS Energy Lett., 2021, 6, 893–899), and specifically supplemented the\nfine Cu 2p XPS spectra of Ru Cu /CeO catalyst in the high binding energy region\n0.6 1 2\n(~930–958 eV), where characteristic satellite peaks served as key fingerprints for\nidentifying Cu2+ (Supplementary Fig. 35). Analysis demonstrated that:\n1. Reference sample CeO /CuO clearly showed strong satellite peaks near ~944 eV,\n2\nexplicitly confirming the existence of Cu2+;\n2. In sharp contrast, the corresponding spectra of Ru Cu /CeO catalyst\n0.6 1 2\nthroughout the entire reaction time window (0 to 120 min) always showed no\nobservable distinct satellite peak features;\n3. Additionally, the main peak binding energy position of Cu in Ru Cu /CeO\n0.6 1 2\nexhibited significant differences from the Cu2+ main peak in the reference sample,\nmore closely resembling characteristic values of Cu0/Cu1+.\nComprehensively considering the absence of satellite peaks, significant shift of\nmain peak binding energy position, and monitoring results across the full reaction\ntime series, we confirmed that no Cu2+ species was generated during the oxidation\nprocess on Ru Cu /CeO catalyst, thus eliminating the possibility of O causing\n0.6 1 2 2\nover-oxidation of Cu to Cu2+. These results have been incorporated into the revised\nmanuscript and are also attached below, with new content highlighted in yellow.\nSupplementary Fig. 35 | Cu 2p quasi in situ XPS spectra of CeO /CuO and\n0.6 1 2\nThe valence state of the Cu active sites was monitored using in situ X-ray\nphotoelectron spectroscopy (XPS). During the initial reaction phase under\nconcentrated solar irradiation (0–15 min), the Cu LMM Auger spectra exhibited only\nthe characteristic peaks of metallic Cu (Cu0; 918.6–919.4 eV). At 30 min, Cu1+\nspecies emerged (913.4–913.9 eV), and their relative abundance progressively\nincreased to 58% as the reaction proceeded further (Fig. 3f)23. No Cu2+ species were\ndetected in the higher binding energy range during the quasi in situ XPS analysis\n(Supplementary Fig. 35)…\nPreparation of catalysts CuO/CeO\n2\nmethod followed by calcination. Specifically, 1.5 mmol of Cu(NO ) ·3H O and 1.0\n3 2 2\nmmol of Ce(NO ) ·6H O were dissolved in 40 mL of an aqueous solution containing\n3 3 2\n2.3 M glycerol with vigorous stirring at room temperature. The resulting solution was\ntransferred to a Teflon-lined stainless-steel autoclave and hydrothermally treated at\n180 °C for 6 h. After cooling to ambient temperature, the solid product was recovered\nby centrifugation and washed repeatedly with absolute ethanol (≥3 times). The\nprecipitate was dried at 80 °C for 12 h under vacuum. The dried precursor was then\ncalcined in static air using a muffle furnace. The temperature was ramped to 350 °C at\n5 °C·min−1 and held for 2 h, yielding the final CuO/CeO catalyst.\n“The manuscript has been improved obviously, and can be accepted now.”\nWe are grateful for the thoughtful comments and recommendations provided by this\nreviewer. Thank you for your valuable input.\nReviewer #3:\n“The authors have addressed my comments well, I therefore recommend publication\nat this stage.”\nWe are grateful for the thoughtful comments and recommendations provided by this\nreviewer. Thank you for your valuable input.\nReviewer #4:\n“The author has addressed my concerns and agrees to accept the current version.”\nWe are grateful for the thoughtful comments and recommendations provided by this\nreviewer. Thank you for your valuable input.\nPoint-by-Point Responses to Reviewers’ Comments\nReviewer #1:\n“I thank the authors for the rigorous consideration of my comments. I can now\nrecommend publication.”\nWe are grateful for the thoughtful comments and recommendations provided by this\nreviewer. Thank you for your valuable input."}, {"round": 3, "reviewer_comments": {"reviewer_1": "I thank the authors for the rigorous consideration of my comments. I can now recommend publication."}, "author_response": "We are grateful for the thoughtful comments and recommendations provided by this reviewer. Thank you for your valuable input."}]

Decision letter