Inverse decoration of TiO_x to NiSn alloy nanoparticles for efficient hydrodeoxygenation of m-cresol

Domain: chemistry
Published: 2025-12-19
Editorial outcome: major_revision

Abstract
Hydrodeoxygenation(HDO)ofphenolicsiscrucialforlignin-to-fuelproduc-tionviafastpyrolysis.ThereactionunderatmosphericH2pressureofferscompatibilitywithpyrolysisconditions,higharomaticselectivityandlowH2consumption,butsuffersfromcoking-inducedcatalystdeactivation.Inthiswork,wereportaTiO x-decoratedNiSn/SiO 2catalyst(Ti-NiSn/SiO 2),achieving100%deoxygenationselectivityandenhancedstabilityinm-cresolHDO.Thesuperiorperformancestemsfrom:(i)theinterfacialsynergybetweenTiO xandNiSnalloythatfacilitatesC-Obondcleavagewithareducedenergybarrier;(ii)thegeometricisolationandelectron-donatingpropertiesofSn,whichsuppressundesirablesidereactionsandmitigatecokeformation;and(iii)theinverseTiO xdecorationstrategy,whichenableseffectiveinterfacechemistrywhileminimizingacidicsitesthatcouldotherwiseacceleratecoking.Thisstudypresentsadesignstrategyforconstructinginverseoxide–alloyinterfacecatalysts,offeringmulti-facetedadvantagesforHDOandothercomplexcatalytictransformations.

Introduction
Fastpyrolysisisanefficienttechnologyonbiomassconversiontosustainableliquidfuels,whichcanproducebio-oilwithayieldupto75wt%1,2.Butthebio-oilpresentsshortcomingssuchashighoxygencontentandpoorstability,requiringhydrodeoxygenation(HDO)treatmenttoimproveitsqualitybeforeapplicationasfuel.HDOisalsoakeyreactionincatalyticfastpyrolysis,andthedevelopmentofeffectiveHDOcatalystsoperableunderambient-pressureconditionscouldfurtherimproveoverallprocessintegration(Fig.1a)3,4.Amongcommonoxygen-containingstructuresinbio-oil,cleavageofthephenolicC-Obondisthemostchallenging5.Thus,thedevelopmentofhigh-performancephenolicHDOcatalystshasattractedwidespreadattention.Despitethis,mostreportedHDOreactionsoperateinbatchsystemsorrequirehighH2pressure,whilevapor-phaseHDOstudiesunderatmosphericpressurethatcompatiblewithpyrolysisconditionsarestilllimited6.

EffectiveHDOcatalysistypicallyrequiresnotonlyC-Obondactivationbutalsohydrogenationanddehydrogenationsteps.TominimizeH2overconsumption,suppressingaromaticringhydrogenationisessential.Additionally,thecatalystmustinhibitbothC-Cbondcleavageandcokingsidereactionstoensuretargetproductselectivityandmaintainlong-termstability.Theserequirementsaredifficulttoachievewithmonotransitionmetalcatalysts,whereasinterfacialstructuresofferapromisingsolutionduetotheirmultifunctionalityandflexibledesignability(Fig.1b)7.Forinstance,numerousstudieshavereportedthatconstructingmetal-acidic/oxophilicsiteinterfacescansignificantlyenhancebothactivityandselectivityinphenolicHDOreactions.Insuchsystems,theacidsitescanbeprovidedbyamorphousSiO 2-Al 2O 3,zeolites,orotheracidicsolids,whiletheoxophilicsitesusuallyoriginatefromtransitionmetalsormetaloxideswithstrongoxygenaffinity8.Onsuchinterfaces,ithasbeenrevealedthatthephenylringpreferentiallyadsorbsonthemetalsite,whilethehydroxylgroupofphenolsbindstoneighboringacidic/oxophilicsites.ThissynergisticactivationleadstoalowerenergybarrierforC-OcleavageandenhancedHDOactivity,incontrasttolessselectivephenylringactivationonmetalsitesaloneortheinefficientoxygenactivationonacidic/oxophilicsitesalone9,10.However,thephenolicreactantstendtoformcondensed-ringcompounds,leadingtocatalystdeactivationbycoking11,12.Theacidic/oxophilicsitesfacilitatethecondensationprocessofphenolicintermediatesandtherebyacceleratecoking13–15.Forinstance,severalstudieshavereportedfasterdeactivationonacidic/reducibleoxidesupportedcatalyststhanthoseoninertSiO 2supportedcatalysts16,17.

Unliketheabovestrategies,someresearchershaveusednon-acidic/non-oxophilicmaterialstoconstructinterfaceactivesiteswithmetals,achievingprogressinimprovingcokeresistance(Fig.1b).Yangetal.reportedthatasmallamountofnitrogendopinginthecarbonsupportreducesthedeactivationrateofFeparticlesalmostbyoneorderofmagnitudeinm-cresolHDO,whichisattributedtothereducedoxygenaffinityofFebyNspecies18.Telesetal.investigatedtheinfluenceofCe/ZrratioonphenolHDOperformanceoverPd/Ce xZr 1-xO 2catalysts.TheyfoundthatCe-enrichedcatalystsexhibithigherstability,whichisattributedtothereducedoxophilicity19.However,inthesecases,theenhancedcatalyststabilitycomeswithasubstantialsacrificeinactivity.Thus,engineeringphenolicHDOcatalystswithbothhighefficiencyandanti-cokingstabilityunderatmosphericpressureremainsasignificantchallenge.

WepreviouslyexploredbimetalliceffectsforHDOofm-cresolandrelatedmolecules20,21,andobservedthatwhiletheadditionofSnpromotertoNi/SiO 2catalystinhibitsthefurfuralHDOreactivity,itisabletoenhancethedeoxygenationselectivityandrelievecokingontheactivesites,instarkdifferencetotheacidic/oxophilicsitepromotedNicatalysts21.Moreover,SnalloyedNicatalystshavealsobeenreportedtoshowenhancedstabilityinreforminganddehydrogenationreactions,astheelectronicinteractionbetweenSnandNipreventscarbonnucleationonNiactivecenter22–24.

Buildingontheaforementionedinsights,inthiswork,wepresentaninverseTiO xdecorationstrategyonNiSnalloynanoparticlesupportedonSiO 2(denotedasTi-NiSn/SiO 2,Fig.1c),asadistinctandefficientcatalystfortheHDOofm-cresol—arepresentativephenoliccompoundderivedfromlignindecomposition.Takingthemultipleadvantagesof(1)interfacialchemistrybetweenTiO xandNiSnalloyinloweringC-Oactivationbarrier,(2)theelectronicandgeometricmodificationimpartedbySntosuppresssidereactionandmitigatecokedeposition,and(3)theinversestrategytominimizeTiO xcontentandreducecoking,theresultingcatalystexhibitssignificantlyenhancedactivity,deoxygenationselectivity,aswellasstabilityforHDOofm-cresolat350°CandatmosphericH2pressure.Theseimprovementsarenotablysuperiorcomparedtobenchmarkcatalysts,includingNi/SiO 2,NiSn/SiO 2,Ni/TiO 2,NiSn/TiO 2aswellasinverseTi-Ni/SiO 2.Thestructuresofthesecatalystswerecomprehensivelyinvestigatedthroughdetailedcharacterization,whiletheHDOmechanismandthesynergisticeffectattheTiO x-NiSnalloyinterfacesiteswereexploredbydensityfunctionaltheory(DFT)calculationstoprovidecriticalinsightsintothestructure-activityrelationship.Thisstudyoffersarationaldesignstrategyfordevelopinghigh-performanceandstableHDOcatalystsbasedonearth-abundantelements.

Results
BoostingHDOperformanceandstabilityoninverseTiO x-NiSninterface

Firstly,theinterfacialeffectonm-cresolHDOperformanceoverNibasedcatalystswereinvestigated.Catalystswith2wt.%NiloadingonSiO 2andTiO 2weresynthesizedbyincipientwetnessimpregnationmethodandcomparedtoNiSnbimetalliccatalystswiththesameNiloading.HereSiO 2wasselectedasaninertsupport,whereHDOisexpectedtooccursolelyoverthemetal/bimetallicsurface.Incontrast,TiO 2waschosenasanactivesupportwhereTicationsatthemetal-supportinterfacecanparticipateinthereaction.Thebasicelementloading,crystallineandmorphologicalcharacterizationsofthesecatalystsarepresentedinSupplementaryTable1,SupplementaryFigs.1–5andSupplementaryNote1.Thegas-phaseconversionofm-cresolwasstudiedinafixed-bedreactorattemperatureof350°CunderatmosphericH2pressure.Asexpect20,C-ChydrogenolysistoCH 4andphenolpredominantlyoccurredoverdeoxygenationtotolueneonthemonoNiactivesites,leadingtopoordeoxygenationselectivityofNi/SiO 2catalyst(Fig.2a).NiparticlessupportedonTiO 2exhibitedloweroverallactivitybutenhancedyieldandselectivitytowardtoluenecomparedtothosesupportedonSiO 2.Previousstudieshaveshownthatthistrendinreactivityistheresultofstrongmetal-supportinteraction(SMSI)betweenNiandTiO 2,wherereducedTiO xspeciesmigratedtoNisurfaceduringreductionprocess25.ItpreventssinteringofNiparticles,evidencedbytheirsmallersizeonTiO 2.Inaddition,theformationofNi-TiO xinterfaceslowerstheenergybarrier,therebyenhancingdeoxygenationactivity26.Furthermore,partialsurfacecoveragebyTiO xspeciesdecreasesthenumberofexposedNisites,suppressingthestructure-sensitiveC-Chydrogenolysissidereaction27andconsequentlyreducingtheoverallconversionofm-cresol.

TheperformanceofsupportedNiSnalloycatalystsisalsoshowninFig.2a.Firstofall,unlikepureNiphasethatmainlycatalyzesC-Chydrogenolysis,thecatalystscontainingNiSnalloyactivephasearehighlyselectivefordeoxygenationreaction,evenatallconversionlevels(SupplementaryFig.6).ThiscanbeattributedtothegeometricisolationeffectofSnwhichsuppressesthestructuresensitiveC-Chydrogenolysissidereaction.Secondly,comparisonbetweenNi/SiO 2andNiSn/SiO 2showsthatalloyingNiwithSnreducesthetotalactivitybutenhancesthetolueneyield.SimilartothefindinginfurfuralHDO,theSnatomsonsurfacenotonlyoccupytheNiactivecenters,butalsomodifytheirchemicalnature,therebyenhancingtheactivityofNiinthetargetdeoxygenationreaction21,28.Thirdly,itisinterestinglytonotethattheuseofTiO 2supportreversestheactivitytrendbetweenNiandNiSnsites.TheNiSn/TiO 2catalystshowsthreetimeshigherm-cresolconversionthanthatofNi/TiO 2(Fig.2a).Lastbutnotleast,incontrasttomonometallicNiphaseonTiO 2,whichdetersm-cresolconversionrelativetoNi/SiO 2,theNiSnalloyonTiO 2showsalmostthreetimeshigherm-cresolconversionthanthatonSiO 2.

Subsequently,m-CresolandH2probecharacterizationswereinvestigatedtoelucidatetheadsorptionandactivationofreactantsontheactivesite,whicharekeyfactorsdeterminingreactivity(SupplementaryFigs.7–9andSupplementaryDiscussion1).In-situm-cresoladsorptiondiffusereflectanceinfraredFouriertransformspectroscopy(DRIFTS)inSupplementaryFig.7demonstratesthedonor-acceptorinteractionbetweenoxygenatomofm-cresolandLewisacidsitesonTiO 2,whichisstrongerthantheH-bondinginteractionbetweenm-cresolandSiO 2support13,14.CombinedwithpreviousDFTstudies,theadsorptionconfigurationsofm-cresolonmetalsurfaceandmetal-TiO xinterfaceareshowninFig.2b.m-Cresolbindstometalsitesthroughphenylringwiththehydroxylgroup(-OH)tiltingawayfromsurface,whiletheTiO xattheneighborofmetalsitescaninteractwiththeOatomin-OHgroup26.SuchadsorptionconfigurationattheinterfacesitefacilitiestheeffectiveactivationofC-Obondinm-cresol,thusresultinginlowerenergybarrierfordeoxygenationreaction(SupplementaryFig.8).ForH2activation,thehydrogen-deuteriumtemperature-programedsurfacereaction(H2-D2TPSR)indicatesthattheadditionofSntoNi/SiO 2significantlypreventsH2dissociation(SupplementaryFig.9),consistentwithpreviousstudiesandDFTcalculationwhichshowedanenhancedenergybarrierforH2dissociationontheNiSnalloysurfacecomparedtothepureNisurface21,28.Fortunately,thisdrawbackcanbemitigatedthroughtheformationofNiSn-TiO xinterface,whichisalsosupportedbyTPRresults(SupplementaryFig.10).AllthesefindingsunderscorethecrucialroleofbothTiO xandSn,aswellastheirsynergisticeffectinmodulatingthechemicalnatureattheinterfacesite,thusleadingtoenhancedphenolicHDOperformance.

Thecatalyticstabilityandtheoxygentemperatureprogramedoxidation(O2-TPO)profileofspentcatalystsarefurtherevaluatedandshowninFig.2candSupplementaryFig.11.TheNi/TiO 2deactivatesatasignificantlyhigherrateascomparedtoNi/SiO 2.Correspondingly,thetotalcokedepositiononNi/TiO 2istwotimeshigherthanthatonNi/SiO 2(SupplementaryTable2).ThiscanbeascribedtotheacidicnatureofTiO 2support(SupplementaryFig.12andSupplementaryTable3),whichpromotescondensationofm-cresol,leadingtoincreasedcokeformation29.Asexpected,theintroductionofSnenhancesHDOstabilityonbothSiO 2andTiO 2supportedNicatalysts.Therefore,thecokingbehaviorofcatalystsinm-cresolHDOcanbeillustrated.AsshowninFig.2d,cokeformationoccursattwotypesofactivesites:metallicNisitesandTiO xacidsites.MetalinducedcokingcanbesuppressedthroughtheformationofNiSnalloy,whileacidinducedcokingcanbemitigatedbyreplacingtheacidicTiO 2supportwithinertSiO 2.

TheNiSn/SiO 2exhibitsthehighestanti-cokingstability,butitsactivityremainspoorintheabsenceofTiO 2support.ConsideringthatonlytheoxophilicTiO xspeciesadjacenttotheNiSnalloycontributetothesynergeticactivationofm-cresol,whileexcessacidicsitesonTiO 2exacerbatecoking,wesoughttoexplorewhetheracatalystcomposedoftraceTiO xonNiSnparticlescouldachieveanewlevelofcatalystperformance.Theinversestructurewassynthesizedbyslowhydrolysisoftetrabutyltitanateovertheas-preparedNi/SiO 2orNiSn/SiO 2catalysts,aspresentedinFig.2e.TheobtainedcatalystwasnamedasxTi-M/SiO 2(M=NiorNiSn),wherexreferstothenominalmolarratioofTitoNi.O2-TPOanalysisofthefreshcatalystsindicatesthatthecarbonaceousspeciesfromtetrabutyltitanatearealmostremoved(SupplementaryFig.13andSupplementaryTable4).TheactivitycomparisonamongthesecatalystsisshowninFig.2f.Specifically,overNi/SiO 2,theinverseloadingofTiO xcausedadecreaseintotalconversionbutanenhancedyieldtotoluene.ThiswasconsistentwiththeactivitytrendbetweenNi/SiO 2andNi/TiO 2,andcouldalsobeattributedtotheSMSIeffectbetweenTiO xandNinanoparticles.Asexpected,moreTiO xonNi/SiO 2leadedtofurtherinhibitioninreactivity.Conversely,thedecorationofTiO xonNiSn/SiO 2significantlyenhancedthedeoxygenationreaction,withthem-cresolconversionandtolueneyieldincreasedbyalmost2.7times.Notably,itsactivitywascomparablewiththatoftheNiSn/TiO 2catalyst.Moreinterestingly,the0.5Ti-NiSn/SiO 2catalystexhibitedgreaterstability(Fig.2g),withlesscokeaccumulationasindicatedbyO2-TPO(SupplementaryFig.13).CombinedwithNH3temperature-programmeddesorption(NH3-TPD)resultsinSupplementaryFig.12,itdemonstratesthattheinverseTiO xloadingoutperformsconventionalTiO 2supportinsuppressingacidinducedcoking.

Elucidatingtheanti-cokingadvantageofinverseTiO x-NiSninterface

Tofurtherelucidatetheanti-cokingadvantageofinverseTiO x-NiSninterface,thecoverageofactivesitesbycokeafterm-cresolHDOisinvestigatedbyanin-situprobereactionofisopropanol(Fig.3a).Generally,metalsitescatalyzethedehydrogenationofisopropanoltoacetone,whileacid/oxophilicsitecatalyzethedehydrationofisopropanoltopropene30–32(Fig.3b).Therefore,thecokecoverageonthemetalandTiO xsitescanbeestimatedfromthepercentagedecreaseinacetoneandpropeneyields,respectively,afterm-cresolHDO.Here,theHDOreactionwasconductedfor5min(asinitialcatalyststate)and125min(ascokedepositedcatalyststate).

AsshowninFig.3c,acetoneisthemainproductonNi/SiO 2,indicatingthatmetallicNiactivesitesdominatethecatalystsurface.Duringthe2hHDOtest,m-cresolconversiondecreasedby51%,closelymatchingthe52%decreaseinacetoneyield.Thesecomparableresultsdemonstratethattheisopropanolprobereactioncaneffectivelyreflectcokecoverageonactivesites.On0.5Ti-Ni/SiO 2,propeneformationisobservedduetothesurfaceacidityprovidedbyTiO x.The66%decreaseinm-cresolconversionismorepronouncedthanthatofNi/SiO 2,consistentwiththemoreseveredeactivationobservedathigherconversionlevelsinFig.2c.Interestingly,whiletheacetoneyielddeceasesby53%,similartoNi/SiO 2,thepropeneyielddecreasesonlyby27%on0.5Ti-Ni/SiO 2.ThisobservationindicatesthatcokepredominantlycoversmetallicNisites,leadingtodeactivationinm-cresolHDO,whileTiO xsitesexperiencelesscoverage.

OnNiSn/SiO 2,propeneyieldisnegligiblecomparedtoacetoneyield,demonstratingthattheSnpromotertoesnotintroduceacidsites.Theacetoneyieldremainsconstantafter2hHDOreactionofm-cresol,confirmingtheinherentanti-cokingpropertyofNiSnalloy.AftertheinverseintroductionofTiO x,propeneisformedbutataloweryieldcomparedtoacetone.Thedistinctproductdistributionsbetween0.5Ti-NiSn/SiO 2and0.5Ti-Ni/SiO 2duringisopropanolreactionmaybeattributedtodifferentTiO xstructures,asevidencedbyRamanresults(SupplementaryFig.14).ThecontrolexperimentsoncatalystswithoutNiorNiSn(SupplementaryFig.15)furtherdemonstratethathighlydispersedcrystallineTiO xprovidesahigherdehydrationactivitythantheamorphousTiO x.Comparedto0.5Ti-Ni/SiO 2,the2hm-cresolHDOprocesshasnegligibleeffecton0.5Ti-NiSn/SiO 2,suggestingthatNiSnalloynotonlypossessesintrinsicanti-cokingpropertybutalsosuppressescokedepositiononadjacentTiO xsites.Consequently,theinverseTiO x-NiSninterfaceenablesbothhighactivityandremarkablestabilityinm-cresolHDO.

GeometricandelectronicstructureofinverseTiO x-NiSninterface

Tounderstandtheefficientm-cresolHDOperformanceofinverseTiO x-NiSninterface,thecatalystsweresubjectedtodetailedcharacterization.

Asnoted,thequantifiedTicontentis1.03wt%and1.13wt%onthe0.5Ti-Ni/SiO 2and0.5Ti-NiSn/SiO 2catalysts,respectively,asdeterminedbyInductivelyCoupledPlasmaOpticalEmissionSpectrometry(ICP-OES,SupplementaryTable1).High-angleannulardarkfieldscanningtransmissionelectronmicroscopy(HAADF-STEM)correspondingwithelectronenergy-lossspectroscopy(EELS)analysiswasperformedtovisualizetheinteractionbetweentheTiO xspeciesandtheNiorNiSnnanoparticles.AsshowninFig.4aandb,athinTiO xlayerpartiallycoveredthesurfaceofNiandNiSnalloynanoparticlesfor0.5Ti-Ni/SiO 2and0.5Ti-NiSn/SiO 2catalysts,respectively.TheTiO xspecieswereclearlydispersedaroundtheNiorNiSnparticles,ratherthanontheinertSiO 2support,indicatingastronginteractionbetweenNi/NiSnandTiO xafterreduction.Inaddition,theEELSmapping(Fig.4b)demonstratedtheclosedistributionbetweenNiandSn,indicatingtheformationoftheNiSnalloyontheNiSn/SiO 2-basedcatalyst.

TheTiO xstructureontheNi/NiSnalloysurfacewasfurtherexaminedbyRamanspectra(SupplementaryFig.14).Forcomparison,theRamanspectraofTiO 2-supportedNiandNiSncatalystsarealsoincluded,whichwerecharacterizedbytheEgmodeofanataseat143cm−1asthestrongestsignalforbothanataseTiO 2andP2533.Onthe0.5Ti-Ni/SiO 2catalyst,theEgmodehadblue-shiftedto149cm−1andbroadenedinthefullwidthathalfmaximum(from~18to~24cm−1),whichwasrelatedtophononconfinementandcouldbeascribedtothedecreaseoftheTiO xthicknesswithrespecttotheTiO 2nanoparticles34.However,anyRamansignalofTiO xspecieswasundetectablewith0.5Ti-NiSn/SiO 2.IncasethatlimitedTiO xcontentonthiscatalystcausedtheweakresponsetoRamanlaser,the1Ti-NiSn/SiO 2withtheTicontentbeingdoubledwastested,butstillshowednosignal.ItdemonstratedanamorphousstructureofTiO xontheNiSnalloyparticles35,possiblyderivingfromtheuniqueinteractionbetweenTiO xandNiSnalloyphases.

PossiblestructurechangesofNiorNiSnalloyafterTiO xcoatingwerefirstexaminedbyXRD.TheresultsshowedidenticaldiffractionpeaksbeforeandafterTiO xloadingforbothNi/SiO 2andNiSn/SiO 2catalysts(SupplementaryFig.16),demonstratingthatthebulkactivephaseofNiparticlesorNiSnalloysremainsunchangedafterTiO xcoating.Inaddition,noTiO xrelateddiffractionpeakswereobservedduetothehighdispersionofTiO xonthesurface,consistentwiththeRamanspectra.

TheextendedX-rayabsorptionfine-structure(EXAFS)analysiswasfurtherperformedtocharacterizethecoordinationstructureofNiandNiSnphasesineachcatalyst.NiK-edgeX-rayabsorptionnear-edgespectrum(XANES)inSupplementaryFig.17arevealedthatthefingerprintingfeatures(includingtheareaofpre-edgeandwhite-line)ofallNiorNiSn-basedcatalysts,bothbeforeandafterTiO xcoating,resemblethoseofNifoilratherthanNiO.ThisindicatedalmostfullyreductionofNiOineachcatalyst.TheFTk2-weightedNiK-edgeEXAFSfurtherdemonstratedanidenticalcoordinationenvironmentofNiatomsbetweenNi/SiO 2and0.5Ti-Ni/SiO 2,botharemetallicNiparticles.WhilethereareNi-SnandNi-NicoordinationinbothNiSn/SiO 2and0.5Ti-NiSn/SiO 2,indicatingtheformationofNiSnalloyintheNiSn-basedbimetalliccatalysts(SupplementaryFig.17b,SupplementaryTable5).TheaboveobservationconfirmedtheNiandNiSnalloyphasesremainedinthesamestatebeforeandafterTiO xcoating,consistentwiththeXRDresults.

AlthoughXRDandEXAFSrevealedthatthebulkstructureofNiorNiSnalloysremainsunchangedafterTiO xdecoration,subtledifferencesinthesurfacestructuremightnotbedetectablebythesebulkcharacterizationtechniques.Surface-sensitivetechniques,suchasX-rayphotoelectronspectroscopy(XPS)andin-situCODRIFTS,werethereforecrucialtouncoverpotentialmodificationsattheatomiclevelonthecatalyst’ssurface,whichcouldsignificantlyinfluencecatalyticperformance.AspresentedinFig.4c–fandSupplementaryFigs.18–19,priortoCOadsorption,thecatalystwasin-situreducedinH 2at400°Cfor1h.AfterexposuretoasaturatingdoseofCOat30°CandsubsequentpurgingtoremovephysicallyandweaklychemicaladsorbedCO,twodistinctbandswereobservedonNi/SiO 2.Anintensebandcenteredat2077cm−1andabroadbandat~1940cm−1wereobservedonNi/SiO 2(Fig.4c),whichwereassignedtolinearlyadsorbedCOorsubcarbonylspeciesatoptheunsaturatedlow-coordinatedNiatom,andbridgedadsorbedCOonclose-packedNisites21,36–40.ThedecorationofTiO xonNisurface(0.5Ti-Ni/SiO 2)significantlyreducedtheintensityoflinear-adsorbedCOandaslightredshiftto2075cm−1,whilethebridged-CObandremainedunaffected(Fig.4c).ThisobservationsuggestedthatTiO xspeciespreferentiallyinteractwithNiatomsinlow-coordinatedgeometries,coordinatingwiththesesitesandalteringtheirelectronicproperties.TheTiO xcoverageonNisitewasdeterminedas53.9%byCOpulsedchemisorption(SupplementaryTable6).ThepartiallyelectrondonationfromTiO xtoNienhancedtheCOadsorptionstrengthonNi(red-shift).SuchelectroninteractionbetweenTiO xandNiwasfurtherverifiedbyXPSanalysis(SupplementaryFig.20)andalignedwithpreviousreports41.TheCOadsorptionspectrarevealednotabledifferencesbetweenNi/SiO 2and0.5Ti-Ni/SiO 2(SupplementaryFig.18).ForNi/SiO 2,uponexposureto5kPaCOfor1minute,abandat2085cm−1appearedandintensifiedovertime,eventuallyblue-shiftingto2090cm−1duetodipole-dipoleinteractionsbetweenadsorbedCOmolecules.Asecondarybandcenteredat2056cm−1emergedanddominatedatequilibriumCOpressure.Thisband,assignedtoNi(CO) 4speciesphysicallyadsorbedonNiand/orSiO 2support,disappeareduponArflushing,suggestingitsformationinvolvedsubcarbonylintermediates(~2090cm−1)ondefectedNisurfaces,whichcouldleadtonickeltetracarbonylformation36–38,40.ComparativespectraatequilibriumCOpressure(Fig.4e)demonstratedthatTiO xdecorationonNireducedthenumberofdefectNisites,indicatedbythediminishedintensityofthe2090cm−1band.However,theNi(CO) 4bandat2056cm−1intensifiedandslightlyred-shiftedto2054cm−1,suggestingthattheTiO x-modifiedNisurfacewasmoreactiveinconvertingNisubcarbonyltoNi(CO) 4.TheredshiftfurthersupportedelectrontransferfromTiO xtotheNisurface.ThisbehavioralignedwithpreviousstudieslinkingNi(CO) 4formationtodeactivationmechanismsinCOhydrogenation,asNi(CO) 4decompositioncouldleadtonickelcarbideformationandNiparticlessintering42.Consequently,thetendencyofTiO x-modifiedNisurfacestopromoteNi(CO) 4formationmaybeasignaturefortheirfasterdeactivationduringHDOreactions(Fig.2c).Instarkcontrast,theNi(CO) 4specieswereabsentinthespectraofNiSn-basedcatalysts(Fig.4dandfandSupplementaryFig.19),whichmayberelatedtotheiranti-cokingperformance.

BeforediscussingthedifferencebetweenTiO xmodifiedNi/SiO 2andNiSn/SiO 2catalysts,thecomparisonbetweenNi/SiO 2andNiSn/SiO 2wasfirstlyrevealed.Asnoted,incontrasttoNi/SiO 2thatpresentedbothlinear(2077cm−1)andbridge(1940cm−1)COvibrationatthesteadystateofCOadsorption(Fig.4c),onlyonesymmetricalbandcenteredat2066cm−1(linearadsorbedCO)withanarrowfullwidthathalf-maximum(FWHM)of19.2cm−1wasobservedonNiSn/SiO 2,whilethebridgedadsorbedCOonclose-packedNisiteswascompletelydisappeared(Fig.4d).Anyadditionalbandswereundetectableduringtheadsorptionanddesorptionprocess(SupplementaryFig.19).ItindicatedahighlyuniformandisolatedsurfaceNisiteswereformedthroughalloyingwithSn,whichwasresponsiblefortheremovalofC-ChydrogenolysissidereactionthatpreferredonlargeNiensembles27.TheredshiftoflinearCObandfrom2077to2066cm−1demonstratedtheelectrontransferfromSntoNi,agreeingwiththeXPSobservation(SupplementaryFig.20)andpreviousstudiesonNiSnalloy.AfterdecorationofTiO xtoNiSnalloysurface,anobviousdecreasedofCOadsorbedbandintensity,aswellasaslightredshiftto2064cm−1wasobserved(Fig.4d).TheformerwasascribedtothedecreasednumberofexposedNisitesbyTiO xcoating,resultinginthe16.9%TiO xcoverageonNiatoms(SupplementaryTable6).ThelatterphenomenondemonstratedtheelectrondonationfromTiO xlayertoNi,whichwasalsoverifiedbyXPSanalysis(SupplementaryFig.20).ThisobservationisconsistentwiththeelectronicinteractionsidentifiedintheNi-basedcatalysts,furtherreinforcingtheroleoftheTiO xlayerinmodifyingtheelectronicstructureofNiandNiSnactivephases.Inaddition,XPSsurveyscanshowsthatthesurfaceNi/SnratioisnotinfluencedbytheinverseintroductionofTiO xspecies(SupplementaryTable7).

UnderstandingreactivityandmechanismattheTiO x-NiSninterface

AsTiO x-NiSninterfacesiteswerefoundtohavesuperiorreactivityform-cresolHDOtotolueneinrespecttothecounterpartNiSnalloysitesandtheTiO x-Niinterfacesites,aDFTstudywasconductedtoexplorethecatalyticmechanismandrevealthefundamentalfactorsthatdeterminereactivity.TomodeltheNiSnalloyphaseonNiSn/SiO 2catalyst,aNi 3Sn(111)surfacewasselectedassuggestedbyCO-DRIFTSandEXAFS,whileNi(111)surfacewasusedformodelingNi/SiO 2catalyst.TheinterfacesitesweremodelledbyaTi 3O 6clusterdecoratedonNi 3Sn(111)orNi(111)surface,respectively,astheoxidetrimerisusuallyusedtomodeltherelativelysmalloxideparticlesintheinversemetaloxide-metalsystem43–46.TheoptimizedstructurefortheTi 3O 6onNi(111)surfaceisacoplanarcyclicconformationwhereeachTiionadsorbedatthehollowsitesandcoordinatedwithoneterminalObindingwithNiathollowsites,andtwobridgingOliftingawayfromsurface(SupplementaryFig.21).SimilaradsorptionconfigurationhasbeenobservedforTi 3O 6onNi 3Sn(111)surfacebutwithTibindingatopofaNiatomwhileterminalObindingatthebridgesitesofNiduetothegeometricisolationeffectofSn(SupplementaryFig.21).Tomakeoxygenvacancy(Tications)attheinterface,oneterminalOofTi 3O 6clusterwasremovedbyhydrogenatingwithH.Comparablethermodynamicoxygenvacancyformationenergyof0.88eVand0.84eVwereobtainedonpureNiandNiSnalloysurface,whilethefinalstablestructureofTi 3O 5onthetwosurfacesareshowninSupplementaryFig.21.

Thefullcatalysiscycle,includingm-cresoladsorption,C-Ocleavage,m-methylphenylfragment(CH 7*)hydrogenationandoxygenvacancyregenerationstepswereinvestigated(Fig.5andSupplementaryFigs.22–25).TheenergybarriercomparisonindicatesthatC-Ocleavageofm-cresolistheratedeterminesteponallcatalysts.Ingoodagreementwithpreviousworks,m-cresolprefersflatadsorptiononabridgesiteoftheNi(111)surface,withthe-OHand-CH 3grouptiltingawayfromsurface(Fig.5a).Asaresult,thoughtheentropy-correctedadsorptionenergyiscalculatedtobehighas−0.81eV,suchadsorptionmodeonNi(111)leadstohighenergybarrierof1.44eVandareactionenergyof0.53eV(endothermic)forC-Ocleavage(SupplementaryFig.26).Incomparison,onlythephenylringofm-cresolweaklyadsorbstothethreefoldNisitesonNi 3Sn(111)surfacewithpositiveadsorptionenergy,whereboththeCandOatomsinm-cresolarenotbondtoSnatoms(Fig.5a),similarasthatofthefurfuraladsorptiononNiSnalloysurface21,28.Thisconfigurationwithitsweakadsorptionenergyexplainstheexcellentanti-cokingabilityofNiSnalloy.Despiteweakeradsorptionofm-cresolonNi 3Sn(111)comparedtoNi(111),itsOatomisclosertotheNi 3Sn(111)surface,withthenearestNi-Odistanceof2.52Å,lowerthanthecaseof2.68ÅonNi(111)surface.ThiscanbeascribedtotheelectrontransferfromSntoNi,whichfacilitatestheinteractionbetweenhydroxylgroupandNisurface.Interestingly,theC-Ocleavagebarrierisdecreasedto0.83eVwithareactionenergyof−0.13eV(slightlyexothermic).ItdemonstratesthattheNiSnalloysurfaceismorefavorablefordeoxygenationreaction,agreeingwellwiththehighertolueneyieldform-cresolconversionoverNiSn/SiO 2ascomparedtoNi/SiO 2.Inaddition,theisolationofNisitesintheNiSnalloysurfaceisresponsiblefortheremovalofstructuresensitiveC-Chydrogenolysissidereaction,asthisreactionrequiresatleast4-6neighboringNiatomsinthetransitionstateforC-Ccleavage.

Instarkcontrast,theinterfacesitespresentahightendencytowardselectiveC-Obondactivation.AsseeninFig.5aform-cresoladsorptiononTi 3O 5/Ni(111)surface,thephenylringinteractswiththeNiatoms,whereObondstoTication(oxygenvacancy),leadingastrongadsorptionenergyof−1.24eV,andalongerC-Obondof1.46Åascomparedtothe1.38Åforthegasphasem-cresol,indicativeofastrongC-Oactivation.Asexpected,theC-Oscissionrequiresamoderateenergybarrierof0.93eVwithareactionenergyof−0.81eV(exothermic),seenSupplementaryFig.26.Similaradsorptionconfigurationofm-cresolhasbeenobservedonTi 3O 5/Ni 3Sn(111)surface(Fig.5a).ComparedtotheadsorptiononNi 3Sn(111),thethreeCatomsattheneighborof-OHinm-cresolbecomesclosertotheNiatoms,whiletheotherCatomsslightlyliftsawayfromsurface.TheOin-OHisbondingwithTicationsnearby,leadingamoderateadsorptionenergyof−0.22eVandamuchlongerC-Obondof1.53Å,demonstratingastrongtendencytowardselectiveC-Obondactivation.TheenergybarrierofC-Ocleavageisfurtherloweredto0.68eV,andthereactionbecomesmuchmoreexothermicshowingareactionenergyof−1.10eV(SupplementaryFig.26).TheabovecomparisonmanifeststheuniquechemistryofTiO x-NiSnalloyinterfaceform-cresoladsorptionandactivation,aswellasstrongtendencytowardC-Ocleavage,insteadofphenylringactivation,whichcollaboratestoitshighcatalyticperformanceform-cresolHDO.

Methods
Materials
ThecommercialSiO 2supportwaspurchasedfromAladdinScientificCorp.withSBETof200m2/g.ThecommercialTiO 2supportwaspurchasedfromSigma-Aldrich(SKUno.718467,P25withamixedphaseofanataseandrutile,primaryparticlesizeof21nm,quotedSBET=35–65m2/g).AnalyticallypuretolueneandNi(NO 3)2·6H 2OwereobtainedfromShanghaiHushiLaboratorialEquipmentCo.,Ltd.Dimethyltindichloride(98%),triethylamine(99%),ethanol(99.8%),tetrabutyltitanate(99%),m-cresol(99%),andisopropanol(99.5%)werepurchasedfromShanghaiMacklinBiochemicalTechnologyCo.,Ltd.

Catalystpreparation
SynthesisofSn/SiO 2andSn/TiO 2:Inatypicalsynthesis,5.0gofSiO 2orcommercialTiO 2and0.173gdimethyltindichlorideweredissolvedin150mLanhydroustoluene,andstirredatroomtemperaturefor1h.Then12.5mLoftriethylaminewasdropadded,andfurthercontinuouslystirredforanother2hatroomtemperature.Subsequently,themixturewasfiltratedandwashedwithtolueneandethanol,driedat100°Covernight,andfinallycalcinedinamufflefurnaceat580°Cfor3h(afterrampingtothistemperaturewithaheatingrateof2°C/min)toobtainSn/SiO 2orSn/TiO 2catalysts.ThenominalSnloadingis1.86wt.%.

SynthesisofsupportedNicatalysts:ThesupportedNicatalystswerepreparedbyincipientwetnessimpregnationmethod.Inatypicalsynthesis,0.20gNi(NO 3)2·6H 2Owasdissolvedinacertainamountofdistilledwater,anddropaddedto2.0gsupport,i.e.,SiO 2,TiO 2,aswellastheabovesynthesizedSn/SiO 2andSn/TiO 2,respectively.Theamountofdistilledwaterusedhereis4.0gforSiO 2basedsamples,and0.7gforTiO 2basedsamples.Themixturewasground,driedat60°Covernight,andcalcinedat400°Cfor4h(heatingrate:2°C/min)toobtainthesupportedNicatalystsofNi/SiO 2,NiSn/SiO 2,Ni/TiO 2andNiSn/TiO 2,respectively.ThenominalNiloadingisfixedat2wt.%.

SynthesisofinverseTiO x-Ni/SiO 2andTiO x-NiSn/SiO 2catalysts:TetrabutyltitanatewasusedastheTiO xprecursor.Asthetetrabutyltitanatewaseasytobehydrolyzed,wefirstlydissolvedacalculatedamountoftetrabutyltitanateinto4.0gofethanol,andthendroppedtheresultingsolutionto2.0gofas-preparedNi/SiO 2orNiSn/SiO 2catalystandimpregnatedovernight.Herethetetrabutyltitanateamountis0.116gwhenTi/Nimolarratiois0.5.Whileexposingtotheair,theH 2OinairwouldmaketetrabutyltitanatebeslowlyhydrolyzedanddepositedasTiO x.Thecarbonligandwasremovedbycalcinationinairat300°Cfor1h(heatingrate:10°C/min).ThecatalystwasnamedasxTi-M/SiO 2(M=NiorNiSn),wherexreferstothenominalmolarratioofTitoNi.O2-TPOanalysisofthefreshcatalystsindicatesthatthecarbonaceousspeciesfromtetrabutyltitanatearealmostremoved(SupplementaryFig.13andSupplementaryTable4).

Catalystcharacterization
TheelementloadingofcatalystwasdeterminedbyInductivelyCoupledPlasmaOpticalEmissionSpectrometry(ICP-OES)onAgilentICP-OES5110instrument.Beforethemeasurement,thesampledigestionprocessbeganwithweighing0.1gofsampleintoapolytetrafluoroethylenedigestiontube,followedbytheadditionof5mLofconcentratedHNO₃(65%)and2–3mLofHF(40%).Subsequently,thesealedtubeunderwentmicrowave-assisteddigestionusingaprogrammedtemperatureprotocol:thetemperaturewasfirstraisedto120°Cwithin5minandheldfor5min,thenfurtherincreasedto180-200°Cwithinanother5minutesandmaintainedatthisrangefor30-40minutestoensurecompletedigestion.

TheX-raydiffraction(XRD)patternsofdifferentcatalystswerecollectedonaRigakuX-raydiffractometeroperatedat40kVand100mA,usingCuKαradiation.Priortoanalysis,thecatalystswerereducedat400°Cfor1h.

High-resolutiontransmissionelectronmicroscopy(HRTEM),andhigh-angleannulardarkfieldscanningtransmissionelectronmicroscopy(HAADF-STEM)togetherwiththeelementalmappingimageswereacquiredusingaJEOLJEM-2100microscopeoperatingat200kV.Priortoanalysis,thecatalystswerereducedat400°Cfor1h.Theelectronenergy-lossspectroscopy(EELS)wasperformedonaNionU-HERMES100microscopewithaconvergencesemi-angleof32mradatanacceleratingvoltageof60kV.TheNi-Ledge,Ti-LedgeandSn-MedgeEELSspectrashowninFig.4werenormalizedbyintegratingsignalswithintheenergy-lossrangeof850-880,455-475and480-520eV,respectively.TheoverlappingTi-LandSn-Medgeswereresolvedbymultiplelinearleastsquares(MLLS)fitting.

X-rayphotoelectronspectroscopy(XPS)wasperformedonanAXISSuprainstrumentbyKratosAnalyticalLtd.withAlKαX-rays(1489.6eV,150W,50.0eVpassenergy).Thesamplewasfirstlypre-reducedat400°Cfor1hinaquarttubereactor,andthentransferredtoaconductivetapeinagloveboxwithAratmospherewithoutexposuretoair.Subsequently,thesamplewasinstalledinanXPSdeviceusingasealedtransportchamber,strictlyavoidingairduringthewholeprocess.Andallthespectracollectedwerecalibratedwithamorphouscarbonat284.8eV.

Ramanspectraofex-situreducedcatalystswererecordedusingaSenterralaserconfocalRamanspectrometer(Bruker)equippedwithexcitationwavelengthλ=532nm.

H2-temperature-programedreduction(H2-TPR)wasperformedonMicrometricsAutoChemⅡ2910.Thecatalystwasfirstlypretreatedat300°Cfor1hinHeandthencooledtoroomtemperature.Thenthegaswasswitchedto10%H 2/Ar.Afterreachingastablebaseline,thesamplewasheatedto900°Catarrateof10°C/min.TheH 2consumptionwasdetectedbyathermalconductivitydetector.

O2-temperature-programmedoxidation(O2-TPO)measurementswerecarriedoutinareactorwithaquartztube(innerdiameter:6mm),using10%O 2/Argasasoxidant.Themassofthespentcatalystwas50mg,thegasflowratewas10ml/min,andthetemperatureincreaseratewas5°C/min.Beforeoxidation,thecatalystwastreatedinapureArgasatmosphereat100°Cfor1htoremovesurface-adsorbedgas.TheoutletgaswasanalyzedusingthePfeifferOmistarquadrupoleonlineMS,observingthekeycomponentusingthefollowingmassspectrumsignals:H 2O(m/z=18),CO(m/z=28),O 2(m/z=32),Ar(m/z=40),CO 2(m/z=44).

COpulsedchemisorptionwasperformedonthesameinstrument.ThecatalystwasfirstlyreducedinH 2at400°Cfor1h,followedbyArpurgingfor0.5h.Aftercoolingtoroomtemperature,theCOpulsedchemisorptionwasconductedwith0.5mL1%CO/Arperloopuntiltheadsorptionwassaturated.TheoutletgaswasanalyzedusingthePfeifferOmistarquadrupoleonlineMS,observingtheCOsignalwithm/z=28.

H2-D2temperature-programedsurfacereaction(TPSR)experimentswereperformedonthesamesystem.ThefreshsamplewasreducedinH 2at400°Cfor1h,followedbyHepurgingfor0.5h.Aftercoolingtoroomtemperature,D 2andH 2werethenintroducedtothesystem.Untilasatisfactorysignal/noiseratio,thesamplewasheatedto200°Catarrateof5°C/min.Them/zvaluesare2forH 2,4forD 2,and3forHD,respectively.

NH3-TPDcharacterizationwasconductedontheMicromeriticsAutoChem2950HPinstrumentequippedwithaMSdetector.ThecatalystwasfirstlyreducedinH 2at400°Cfor1h,followedbyHepurgingfor0.5h.Aftercoolingto50°C,10%NH 3/Hewasintroducedtothesystemwiththeadsorptionfor0.5h.ThenthephysicallyadsorbedNH 3waspurgedwithHeagainfor0.5h.Thesamplewasheatedto600°Catarrateof10°C/min.ThedesorptionofNH 3isrecordedwithm/z=16inordertoexcludetheinfluenceofH 2O.

InsituDiffuseReflectanceInfraredFourierTransformspectroscopyofCOadsorption(CO-DRIFTS)wasrecordedonaBrukerEquinox55spectrometerequippedwithamercurycadmiumtelluride(MCT)detector.Thecatalystwasfirstlyreducedin-situintheDRIFTScellinH 2at400°Cfor1h,followedbypurgingwithArfor0.5hatthesametemperature.Thecatalystwasthencooledto30°Cbycoolingwater.Aflowof5%CO/Arwasthenintroducedtothesystemuntilsaturatedadsorption,followedbyArpurgingtoremovethephysicaladsorbedCO.

TheX-rayabsorptionfinespectroscopy(XAFS)experimentwasconductedattheNiK-edgeonbeamline1W1BatBeijingsynchrotronradiationfacility(BSRF),whichoperatedat2.5GeVwithacurrentof250mA.ASi(111)doublecrystalmonochromatorwasused.Thephotonfluxat11.58keVwas~1010photon/s.Datawereacquiredinfluorescencemode,usingLytledetector.NifoilandNiOwereusedasstandards.Beforemeasurement,allofthesampleswerereducedinH 2(30mL/min)at400°Cfor1h,andcarefullysealedunderargonprotectioninaglovebox.TheXASdatawereprocessedandanalyzedusingDemetersoftwarepackage47.

Activitytest
Catalystperformancewasevaluatedinatubularpackedbedflowreactoratmosphericpressure.Thecatalystwasreducedat400°Cfor1h(heatingrate:10°C/min)inflowingH 2(30mL/min).Aftercoolingtothereactiontemperature,thereactantwasinjectedthroughasyringepump(KDS100,KDScientific)andvaporizedunderH 2flowat205°Cbeforeenteringthereactor.Theoutletwasheatedto220°Cbeforeenteringtheonlinegaschromatography(Fuli,GC9790Plus)foranalyzationandquantification.Thetypicalreactionconditionsofm-cresolHDOwere:temperature350°C,pressure1atm,H 2/m-cresolmolarratioof60.TheW/F(h)isdefinedastheratioofcatalystmass(g)toreactantmassfeedflowrate(g/h).Theconversionandyieldarereportedinmol%carbon.

Thein-situprobereactionofisopropanolwasconductedusingthesamereactor.Firstly,thereducedcatalystwassubjectedtom-cresolHDOreactionat350°Cfor5or125min,withthesetimesrepresentingthefreshcatalyststateandcokedepositedcatalyststate,respectively.ThenthesystemwaspurgedbyN 2(20ml/min)andcooledto250°C.Afterthat,isopropanolwasinjectedthroughthepumpandtheyieldsofacetoneandpropenewereanalyzedonlineat15mintimeonstream(TOS).Theconversionsofm-cresolandisopropanolareallcontrolledbelow10%byadjustingW/F.

DFTcalculation
DFTcalculationswereperformedusingtheViennaAb-initioSimulationPackage(VASP)48,49.Thecoreandvalenceelectronswererepresentedbytheprojectoraugmentedwave(PAW)methodandplane-wavebasisfunctionswithakineticenergycut-offof500eV50.Thegeneralizedgradientapproximation(GGA)withthePerdew-Burke-Ernzerhof(PBE)exchange-correlationfunctionalwasusedinthecalculations51.AMonkhorst-Packgridof2×2×1wasusedtosamplethesurfaceBrillouinzone,whichwasdeemedappropriatefork-pointconvergencegiventhelargesizeofthesupercell(>130atoms).Ground-stateatomicgeometrieswereobtainedbyminimizingtheforcesontheatomsbelow0.02eV/Å.Thetransitionstateswereobtainedusingtheclimbingimagenudgedelasticband(CI-NEB)methodbyrelaxingtheforcebelow0.05eV/Å.

Accordingtotheexperimentalcharacterizationresults,theNi 3SnintermetallicwasusedtomodeltheNiSnalloy52.ForcomparisonwithNi(111)surface,amorepreferential(111)surfacewasusedtomodelthealloycatalystsurface,withfiveslabsofa6×6unitcellandthetoptwolayersallowedrelaxinginthecalculations.Adistanceof15Åisaddedtothevacuumlayerinthecalculationtoavoidtheinteractionbetweeneachslab.TomodeltheTiO xonNi/NiSnalloysurface,atitaniumtrimer(TiO 3andTi 3O 6)wasdepositedonNi(111)orNi 3Sn(111)surface41,43.TheprimaryobjectiveofDFTstudyistocomparethecatalyticfunctionoftheseinverseinterfacesagainstpureNiandNiSnsurfaces,andtoidentifythecorefunctionalityprovidedbyTiO xandSnspeciesinm-cresolHDOreaction.WhilethelocationofTiO xclusteronlow-coordinatedmetalsurface,suchasstepsites,isevidencedbyCO-DRIFTSresults,thechoiceof(111)surfacemodelshereprovidesawell-definedbenchmarksystemforinvestigatingtheaboveobjective.FurtherdiscussiononthevalidityofthemodelsisprovidedintheSupplementaryDiscussion2andSupplementaryFigs.27–28.

TheGibbsfreeenergychangeinthisworkisdefinedas:
ΔG=ΔE+ΔZPE−TΔS(1)
whereΔEisthedifferenceinDFTelectronicenergies,ΔZPEisthecorrectioninzero-pointenergiesobtainedfromvibrationalfrequencycalculationsperformedonalloptimizedstructures,andTΔSthecontributionofentropy.Theentropyofadsorbedspeciesiscalculatedwithintheharmonicapproximationusingthevibrationalfrequenciesobtainedfromtheoptimizedstructure.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The noteworthy results are the improved on stream performance due to reduced coking. This is a very active area of research and there are lots of groups trying to develop materials for efficient direct deoxygenation of biofuel-related materials to improve the heating value of the materials. As an example, Fuel (334) 2023 \"Enhanced deoxygenation performance and coke resistance of Ni-based catalysts for jatropha oil conversion by rare earth elements\" is one such example. It is often difficult to compare one catalytic paper to another because there are so many variables, but while this paper represents a nice result, it is difficult to describe it as particularly novel or particularly significant. The experimental result is a bit underdeveloped in parts. The uploaded file provides more detail on what aspects need to be expanded. It also notes grammatical errors. As written there is not enough detail in the experimental section for the work to be reproduced, but this could be addressed in a revision. More detail is also needed on number of replicates and error propagation needs to be clearly articulated and error bars included on all catalytic data. The structure of the manuscript undercuts its potential impact. The whole idea of spending 12 pages discussing the first generation catalyst only to then switch to a second generation catalyst does not seem like an efficient or effective way to present this information. The aper would be more impactful if it begins with what works best and perhaps the discussion of the first generation catalyst can be mentioned briefly and mostly moved to SI.", "reviewer_2": "In this manuscript, the authors study TiO2-functionalized, bimetallic catalysts for hydrodeoxygenation of m-cresol, which is a much-studied reaction. This work essentially combines two ideas that have been in the literature for a while: adding Sn to Ni to reduce the tendency toward coke formation, and using TiO2 modifiers on the surface of the catalyst to improve interfacial activity. The authors discover some interesting synergistic effects. For example, whereas TiO2-supported Ni3Sn catalysts are active but not especially stable, producing inverse catalysts in which the TiO2 is located above the catalyst particles produces an active and stable catalyst. The authors largely do an excellent job of characterizing the prepared materials and analyzing the key reaction process with computational methods. Although some of the basic concepts that motivated the paper have been well-established, for me there is clearly sufficient novelty in the results to justify publication in Nature Comm. I recommend that the authors consider the following few points as they revise their manuscript. 1. Regarding Figure 1C, did the authors perform a control in which DRIFTS was done after adsorption of cresol on the support only? Sometimes it can be difficult to use DRIFTS to probe interfacial sites specifically, and some of these compounds may adsorb on support sites far from the interface. 2. The authors claim that the inverse strategy is beneficial because the TiOx on the surface has a lower acidity, allowing improved lifetime. However, I did not see where this proposal was tested experimentally. Can the authors elaborate on the evidence that supports their proposal? An alternative proposal is that TiO2 could block sites that ultimately lead to coking. I understand why the authors proposed that surface acidity is the driving factor, but the manuscript would be improved by describing the evidence for this proposal. 3. Since the TiO2 clusters appear from experimental data to bind to undercoordinated sites on the catalyst surface, did the DFT studies consider use of a stepped surface rather than a (111) surface for any exploratory calculations? Even if not, could the authors comment on whether the (111) surface would be expected to serve as a useful model? 4. Although the mechanistic proposal from the DFT calculations seems similar to that from Janik and coworkers (https://doi.org/10.1016/j.jcat.2019.07.012), the authors may want to comment more on the subsequent steps of the catalytic cycle, as in the prior work. It is not so surprising that a reduced Ti3O5 cluster will interact strongly with the O atom of m-cresol, especially on a Sn-doped surface where the interaction of the cluster with the surface is weaker. The key step on such a surface may be regeneration of the oxygen vacancy, which is only briefly discussed here in reference Figure S17. It wasn’t so clear to me: did the authors compute the activation barrier for oxygen vacancy creation? It appears that the energy required to create such a vacancy was similar for the Ni and Ni3Sn surfaces, which I find somewhat surprising given the other effects of Sn. In any case, I think the authors should talk more about the full cycle. Minor comments / typos: Line 138: “In contract” should be “In contrast” Line 192: “chemistry” should be “chemical” Line 205: the word “spectroscopy” should appear after “transform”, and the acronym should say “DRIFTS”. Line 448: “strength” should be “strong”", "reviewer_3": "This work reports on the study of TiOx-modified Ni(Sn) catalysts for the hydrodeoxygenation of m-cresol through reactivity measurements, characterization, and theoretical calculations. The work follows a consistent narrative which introduces logically increasing complexity, first through the formation of NiSn alloy nanoparticles to improve HDO reactivity and stability over Ni nanoparticles, followed by the decoration of NiSn alloy nanoparticles with TiOx to facilitate reactivity. The authors conclude that TiOx and NiSn phases interact synergistically to enable enhanced HDO by reduced C-O activation barriers and inhibited deactivation mechanisms. However, there are some questions that remain after reading the manuscript as is that should be addressed prior to consideration for publication. Those questions are: 1. Through the manuscript, the authors are inconsistent in their assignment of deactivation behaviors. At times, they cite work which relates the formation of oxide overlayers (SMSI) to the deactivation of Ni sites by physical coverage and prevention of adsorption. Other times, they discuss the formation of coke at acidic TiOx sites. In the end, there does not seem to be a conclusion reached on which is relevant, or whether both contribute in this experimental system and sometimes the authors could be more quantitative. 2. For example, in the comparison of Ni/TiO2 and Ni/SiO2, the TiO2 supported material deactivates from 95 to 5% conversion whereas Ni/SiO2 deactivates from 95% to 50% conversion. Is this consistent with the 2x amount of C deposition for Ni/TiO2 compared to Ni/SiO2? 3. Staying on the note about deactivation – the authors focus on the acidity of TiO2 as a mediator for coke formation and thus deactivation. Upon formation of interaction between Sn and TiOx, the authors observe increased stability – this would lead one to consider that Sn has reduced the acidity of TiOx. How would this happen? What chemical effect would lead to this? 4. The estimation of TiOx coverage by CO DRIFTS is potentially not reliable, which the authors attempt to convey by calling the results “semi-quantitative”. Can the authors provide further detail about their DRIFTS quantification so that an assessment of the validity of their approach can be made? Is the quantification different if absorbance units are used instead of Kubelka-Munk? Is it possible to conduct a more quantitative analysis such as CO pulsed chemisorption? 5. Do the authors have insight into the experimental error for their temperature-dependent reaction measurements made to assess apparent activation barriers? What is the statistical significance of the difference in barriers between these two materials? 6. I have questions about the H/D exchange experiments and their analysis. The authors approach the data with the assumption that H2(D2) activation is rate-limiting in the case of all catalysts. Could it not also be that HD desorption is rate-limiting, and that the data may point towards stronger H(D) adsorption? 7. Has TPO been performed on the as-synthesized 0.5Ti-Ni(Sn)/SiO2 catalysts? The SI notes that hydrolysis of the titanium precursor was allowed to occur in atmosphere and then calcination was performed at 300˚C for 1 hr. Do the authors have evidence that the TiOx-phase formed, which remains amorphous, does not still contain carbonaceous species? 8. The paper assumes that Sn is reduced in-situ (in the discussion and DFT calculations). But it seems likely that Sn may partially oxidize when interaction with TiOx overlayers. Could this be addressed? 9. Further, it seems that Sn incorporation into Ni may change the structure or nature of the TiOx overlayer or alloy surface structure) (e.g. TiOx causes Ni domain aggregation and Sn aggregation). Can the authors comment on this?", "reviewer_4": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": "Point-by-point response to the reviewer comments (Comments in black, Responses in blue and dark red) A list of main changes we have made: 1. We have reorganized the structure of our manuscript to highlight the advantages of the inverse TiO -NiSn/SiO catalyst. x 2 2. We have added ICP, NH -TPD, CO pulse chemisorption, O -TPO of fresh inverse 3 2 catalysts, m-cresol adsorbed DRIFTS on supports, and in-situ probe reaction of isopropanol to provide further experimental evidences. 3. We have added DFT studies of full catalysis cycle. 4. We have improved the figures and checked the grammar in our manuscript. Reviewer 1 Comment 1-1: The noteworthy results are the improved on stream performance due to reduced coking. This is a very active area of research and there are lots of groups trying to develop materials for efficient direct deoxygenation of biofuel-related materials to improve the heating value of the materials. As an example, Fuel (334) 2023 \"Enhanced deoxygenation performance and coke resistance of Ni-based catalysts for jatropha oil conversion by rare earth elements\" is one such example. It is often difficult to compare one catalytic paper to another because there are so many variables, but while this paper represents a nice result, it is difficult to describe it as particularly novel or particularly significant. Response: We sincerely appreciate the reviewer’s recognition of the noteworthy results of our work. We agree with the reviewer that the extensive research variables in the field of HDO make comparative evaluation of catalytic performance rather challenging. For instance, the article mentioned by the reviewer reports that modification of Ni catalyst by Er element improves both activity and coke resistance in jatropha oil deoxygenation at 340 °C under 3 MPa H . The application background, reactant and 2 reaction pressure differ significantly from those in our work, thereby limiting direct comparability between the studies. Since our work focuses on the HDO of m-cresol, a lignin-derived phenolic compound in bio-oils from fast pyrolysis that conducted under atmospheric pressure (Fig. 1a below), we review reports of phenolic HDO reactions in atmospheric fixed-bed reactor and evaluate the stability of different catalysts. There are still hundreds of strongly related studies, indicating that this remains a very active area, as the reviewer pointed out. The representative reports are listed in Table R1: Table R1 Representative reports of phenolic HDO reactions in atmospheric fixed-bed reactor. Catalyst T (°C)a Conv. (%)/TOSc Arene sel. Reference reactant P (bar)b Percentage decreased (%)e Pd/Nb2O5 300 80-40/5 h 100 Catal. Lett. 2023, 153, 2416–2428 m-cresol 1 50% Pt-Fe/CeO2 400 22.7-2.3/100 min 100 ACS Catal. 2021, 11, 12794−12814 m-cresol 1 89.9% Fe/C 350 19-11/5 h 82 ACS Catal. 2020, 10, 7884−7893 m-cresol 0.4 (H2) 42.1% Fe/NC-3.7 350 20-16/40 h 85 ACS Catal. 2020, 10, 7884−7893 m-cresol 0.4 (H2) 20% Pt/NaHB-2 250 95-57/5 h -- Catal. Today 2020, 355, 43–50 m-cresol 1 40% 5Ni2.5Re/SiO2 300 54-30/5 h <50 Catal. Today 2020, 347, 79–86 m-cresol 1 44.4% NiMo/SiO2 350 50-18f/200 min -- ACS Catal. 2019, 9, 7791−7800 m-cresol 1 64% Ni/SiO2-PS 300 82-32/5 h <10 Catal. Today 2019, 330, 149−156 m-cresol 1 61.0% Pt/HBEA 400 52-38/5 h 24-16 ACS Catal. 2016, 6, 1292−1307 m-cresol 1 26.9% MoO3/ZrO2 320 90-62/5.5 h 99 J. Catal. 2015, 331, 86–97 m-cresol 1 31.1% MPA/5%Pt/Al2O3 177 6-5/5 h 80-72 Nat. Catal. 2018, 1, 148–155 benzyl alcohol 1 16.7% MoOx/TiO2 360 20-13/5 h 100 Catal. Today 2025, 454, 115291 phenol 1 35% CuMo/C 330 48-21/3 h 98 Mol. Catal. 2023, 536, 112882 phenol 1 56.3% Pd/SiO2 300 65-47/200 min 65-34 ACS Catal. 2017, 7, 2058−2073 phenol 1 27.7% Pd/Al2O3 300 57-22/200 min 45-22 ACS Catal. 2017, 7, 2058−2073 phenol 1 61.4% Pd/TiO2 300 51-22/200 min 73-75 ACS Catal. 2017, 7, 2058−2073 phenol 1 56.9% Pd/ZrO2 300 66-30/200 min 73-60 ACS Catal. 2017, 7, 2058−2073 phenol 1 54.5% Pd/CeO2 300 60-50/200 min 50-43 ACS Catal. 2017, 7, 2058−2073 phenol 1 16.7% Pd/CeZrO2 300 60-51/200 min 47-36 ACS Catal. 2017, 7, 2058−2073 phenol 1 15% Pt/ZrO2 300 62-37/200 min 70-55 ChemCatChem 2017, 9, 2850 phenol 1 40.3% Rh/ZrO2 300 57-30/200 min 70-65 ChemCatChem 2017, 9, 2850 phenol 1 47.4% Ru/ZrO2 300 52-20/200 min 32-53 ChemCatChem 2017, 9, 2850 phenol 1 61.5% Ni/ZrO2 300 69-29/200 min 34-24 ChemCatChem 2017, 9, 2850 phenol 1 58.0% Co/ZrO2 300 58-25/200 min 19-24 ChemCatChem 2017, 9, 2850 phenol 1 56.9% a reaction temperature. b reaction pressure. c change of conversion with time on stream (TOS). d percentage decrease of conversion with TOS. e selectivity of arene products. f yield. From the survey, we found that most studies have focused on designing bifunctional catalysts to enhance the activity and selectivity in phenolic HDO reactions, whereas relatively fewer have addressed catalyst stability. The above Table R1 shows that most catalysts undergo rapid deactivation in 5 h, with the percentage decrease of conversion ranging from 15% to 89.9%. Fig. 1 Interfacial catalysis strategies for phenolic HDO reactions under atmospheric pressure. a Schematic of HDO units integrated into biomass fast pyrolysis process for biofuel production. b Summary of previous studies on improving metal catalyst performance via interfacial site construction. c Design of the inverse TiO -NiSn alloy interface with efficient HDO performance and anti-coking stability. x A few groups have proposed excellent strategies to improve catalyst stability (Fig. 1b). For instance, Yang et al. reported that a small amount of nitrogen doping in the carbon support reduces the deactivation rate of Fe particles almost by one order of magnitude in m-cresol HDO (ACS Catal. 2020, 10, 7884−7893), and Teles et al. found that Ce-enriched catalysts exhibit higher HDO stability because of the reduced oxophilicity on catalyst (ACS Catal. 2017, 7, 2058−2073). However, in these cases, the enhanced catalyst stability comes with a substantial sacrifice in activity. Thus, engineering phenolic HDO catalysts with both high efficiency and anti-coking stability at atmospheric pressure remains a significant challenge. Our work proposes the inverse TiO -NiSn alloy interface to solve the above problem. x The Ni metal induced coking is suppressed by the formation of NiSn alloy, while the enhanced activity is achieved by the formation of highly active TiO -NiSn alloy x interface. In addition, the inverse interface structure is applied instead of traditional interface structure using TiO support, thus suppressing the acid induced coking. Thus, 2 an effective, non-noble metal catalyst is obtained with high HDO selectivity, enhanced activity and anti-coking stability (Fig. 1c). By the above comparison and discussion, we believe that our strategy represents a meaningful advancement and novelty in the field. Action: Following the comment of the reviewer, we have added the above Fig. 1 to the introduction of manuscript to highlight the advantages of the inverse TiO -NiSn/SiO x 2 catalyst in this field, and the first three paragraphs of introduction have been rewritten: “Fast pyrolysis is an efficient technology on biomass conversion to sustainable liquid fuels, which can produce bio-oil with a yield up to 75 wt%1,2. But the bio-oil presents shortcomings such as high oxygen content and poor stability, requiring hydrodeoxygenation (HDO) treatment to improve its quality before application as fuel. HDO is also a key reaction in catalytic fast pyrolysis, and the development of effective HDO catalysts operable under ambient-pressure conditions could further improve overall process integration (Fig. 1a)3,4. Among common oxygen-containing structures in bio-oil, cleavage of the phenolic C-O bond is the most challenging5. Thus, the development of high-performance phenolic HDO catalysts has attracted widespread attention. Despite this, most reported HDO reactions operate in batch systems or require high H pressure, while vapor-phase HDO studies under atmospheric pressure that 2 compatible with pyrolysis conditions are still limited6. Effective HDO catalysis typically requires not only C-O bond activation but also hydrogenation and dehydrogenation steps. To minimize H overconsumption, 2 suppressing aromatic ring hydrogenation is essential. Additionally, the catalyst must inhibit both C-C bond cleavage and coking side reactions to ensure target product selectivity and maintain long-term stability. These requirements are difficult to achieve with mono transition metal catalysts, whereas interfacial structures offer a promising solution due to their multifunctionality and flexible designability (Fig. 1b)7. For instance, numerous studies have reported that constructing metal-acidic/oxophilic site interfaces can significantly enhance both activity and selectivity in phenolic HDO reactions. In such systems, the acid sites can be provided by amorphous SiO -Al O , 2 2 3 zeolites, or other acidic solids, while the oxophilic sites usually originate from transition metals or metal oxides with strong oxygen affinity8. On such interfaces, it has been revealed that the phenyl ring preferentially adsorbs on the metal site, while the hydroxyl group of phenols binds to neighboring acidic/oxophilic sites. This synergistic activation leads to a lower energy barrier for C-O cleavage and enhanced HDO activity, in contrast to less selective phenyl ring activation on metal sites alone or the inefficient oxygen activation on acidic/oxophilic sites alone9,10. However, the phenolic reactants tend to form condensed-ring compounds, leading to catalyst deactivation by coking11,12. The acidic/oxophilic sites facilitate the condensation process of phenolic intermediates and thereby accelerate coking13-15. For instance, several studies have reported faster deactivation on acidic/reducible oxide supported catalysts than those on inert SiO 2 supported catalysts16,17. Unlike the above strategies, some researchers have used non-acidic/non-oxophilic materials to construct interface active sites with metals, achieving progress in improving coke resistance (Fig. 1b). Yang et al. reported that a small amount of nitrogen doping in the carbon support reduces the deactivation rate of Fe particles almost by one order of magnitude in m-cresol HDO, which is attributed to the reduced oxygen affinity of Fe by N species18. Teles et al. investigated the influence of Ce/Zr ratio on phenol HDO performance over Pd/Ce Zr O catalysts. They found that Ce-enriched catalysts x 1-x 2 exhibit higher stability, which is attributed to the reduced oxophilicity19. However, in these cases, the enhanced catalyst stability comes with a substantial sacrifice in activity. Thus, engineering phenolic HDO catalysts with both high efficiency and anti-coking stability under atmospheric pressure remains a significant challenge.” The first three sentences in Abstract have been revised to: “Hydrodeoxygenation (HDO) of phenolics is crucial for lignin-to-fuel production via fast pyrolysis. The reaction under atmospheric H pressure offers compatibility with pyrolysis conditions, high 2 aromatic selectivity and low H consumption, but suffers from coking-induced catalyst 2 deactivation. In this work, we report a TiO -decorated NiSn/SiO catalyst (Ti- x 2 NiSn/SiO ), achieving 100% deoxygenation selectivity and enhanced stability in m- 2 cresol HDO. The superior performance stems from:”. Comment 1-2: The experimental result is a bit underdeveloped in parts. The uploaded file provides more detail on what aspects need to be expanded. It also notes grammatical errors. As written there is not enough detail in the experimental section for the work to be reproduced, but this could be addressed in a revision. Response: We greatly appreciate the reviewer’s detailed suggestions, which help us improve the manuscript. We have added more information in the experimental section and results, and corrected the grammatical errors. The point-by-point responses to comments in the uploaded file are presented below. Comment 1-2.1: The following sentence is ungrammatical: “On one hand, it prevents the sintering of Ni particles (as indicated by the reduced Ni particle size on TiO ). 2 Response: We thank the reviewer for the comment. Considering that the following two sentences are strongly related to the mentioned sentence, we make modifications together. Action: The sentence and its following two sentences have been revised as “It prevents sintering of Ni particles, evidenced by their smaller size on TiO . In addition, the 2 formation of Ni-TiO interfaces lowers the energy barrier, thereby enhancing x deoxygenation activity26. Furthermore, partial surface coverage by TiO species x decreases the number of exposed Ni sites, suppressing the structure-sensitive C-C hydrogenolysis side reaction27 and consequently reducing the overall conversion of m- cresol.” Comment 1-2.2: This point needs more explanation – where is the integrated area of CO coming from and how does this correspond to the amount of coke on the surface. 2 “Correspondingly, the total coke deposition (based on the integrated area of CO ) on 2 Ni/TiO is two times higher than that on Ni/SiO .” 2 2 Response: We appreciate the reviewer’s suggestion and apologize for omitting this information. The integrated area of CO is obtained from the quantitative analysis of 2 the O -TPO profile in Supplementary Fig. 11, while the amount of coke (g /g ) 2 carbon catalyst is obtained by the calibration of the integrated area. 529 0.005 328 Ni/TiO 2 u.) a. 314 4 ( NiSn/TiO 4 2 = z m/ 310 Ni/SiO 2 NiSn/SiO 278 2 100 200 300 400 500 600 700 T (C) Supplementary Fig. 11 O -TPO profile of spent catalysts. 2 Supplementary Table 2 Coke deposition on different catalysts obtained from quantitative analysis of O -TPO profile in Supplementary Fig. 11. 2 Coke formation Catalyst Integral Area (a.u.) g /g (%) carbon catalyst Ni/SiO 1.77 1.21 2 NiSn/SiO 0.19 0.13 2 Ni/TiO 3.62 2.48 2 NiSn/TiO 1.68 1.15 2 Action: The O -TPO profile in Supplementary Fig. 11 has been presented with baseline 2 for integration, and the corresponding quantitative results have been listed in Supplementary Table 2. The corresponding sentence has been revised as “Correspondingly, the total coke deposition on Ni/TiO is two times higher than that on 2 Ni/SiO (Supplementary Table 2).” The phrase “The stability and carbon deposition of 2 these catalysts” at the beginning of this paragraph has been revised as “The catalytic stability and the oxygen temperature programed oxidation (O -TPO) profile of spent 2 catalysts”. Comment 1-2.3: How often is reduction required? “Prior to analysis, the catalysts were reduced at 400 °C for 1 h”. Response: We thank the reviewer for the comment. To present the information more clearly, we deleted this sentence from the manuscript and verified the catalyst characterization section in the revised manuscript to ensure that all reduced catalyst characterizations include the reduction pretreatment details. Action: “Prior to analysis, the catalysts were reduced at 400 °C for 1 h” has been deleted from the manuscript. In the Catalyst characterization section: “(fresh, reduced, and spent)” has been deleted from the XRD characterization, and “Prior to analysis, the catalysts were reduced at 400 °C for 1 h.” has been added to the end of the paragraph; “Prior to analysis, the catalysts were reduced at 400 °C for 1 h.” has been added after the first sentence of HRTEM characterization. In XPS characterization, “The sample was first pre-reduced in a quart tube reactor” has been revised to “The sample was firstly pre-reduced at 400 °C for 1 h in a quart tube reactor”. Comment 1-2.4: The following sentence is ungrammatical: “rendering it higher activity toward target deoxygenation reaction.” Response: We thank the reviewer for pointing out the ungrammatical expression. Action: The original sentence “but also modify the chemistry nature of Ni sites, rendering it higher activity toward target deoxygenation reaction” has been revised to “but also modify their chemical nature, thereby enhancing the activity of Ni in the target deoxygenation reaction”. Comment 1-2.5: The following sentence is ungrammatical: “It has showed identical IR characteristics between pure Ni and NiSn alloy sites, while the support compositions cause major difference” Response: We thank the reviewer for pointing out the ungrammatical expression. Action: The sentence has been revised to “The results show identical IR characteristics between pure Ni and NiSn alloy sites, while the support compositions lead to major differences.” in the Supplementary Discussion 1 section in the revised SI. Comment 1-2.6: Explain what is occurring here in terms of changes in the electronic structure. “In contrast, the TiO support induced a red shift of 10 cm-1 for ν(CC ) and 2 ring ν(CH ) bands and a red shift of 6 cm-1 for δ(OH) band, demonstrating a stronger 3 adsorption and activation of m-cresol on the Ni/NiSn-TiO interfacial sites compared 2 to the pure metal/alloy surfaces” Response: We thank the reviewer for the comment. The red shift of characteristic bands is ascribed to the donor−acceptor interaction between m-cresol with the Lewis acid site on TiO , which is consistent with the observations reported by Popov et al. (J. Phys. 2 Chem. C 2010, 114, 15661–15670) and Foo et al. (ACS Catal. 2016, 6, 1292-1307). Action: To describe more clearly, the sentence “demonstrating a stronger adsorption and activation of m-cresol on the Ni/NiSn-TiO interfacial sites compared to the pure 2 metal/alloy surfaces.” has been revised as “demonstrating a stronger adsorption and activation of m-cresol on TiO through the donor−acceptor interaction with the surface 2 Lewis acid site1,3.” in the Supplementary Discussion 1 section in the revised SI. Comment 1-2.7: What is the error in these measurements? “As shown in Figure 1E, the NiSn/TiO catalyst exhibited a lower activation barrier of ~63 kJ/mol than that of 2 ~99 kJ/mol on NiSn/SiO ” 2 Response: We thank the reviewer for this important reminder. Based on three repeated experiments, the points are redrawn using the average values and the error bars are added to show the standard deviation of Ln(r ). As shown in Supplementary Fig. 8, Tol the data demonstrate statistical significance with small measurement errors. Despite a slight shift in the E values compared to the original ones, the trend remains the same: act E is lower on NiSn/TiO . act 2 2.0 NiSn/TiO 2 1.5 E = 65.8 4.5 kJ/mol act ) R2= 0.98 h 1.0 / at gc ol/ 0.5 m m ol 0.0 T r NiSn/SiO n ( 2 L -0.5 E = 86.2 8.3 kJ/mol act R2= 0.99 -1.0 1.60 1.65 1.70 1.75 1000/T (K-1) Supplementary Fig. 8 Arrhenius plots of m-cresol deoxygenation to toluene on NiSn/SiO and NiSn/TiO catalysts. Reaction conditions: P = 1 atm, H /m-cresol = 60, 2 2 2 TOS = 20 min, conversion was kept under 10% by adjusting the W/F. The error bars show the standard deviation of Ln(r ) based on three repeated experiments. Tol Action: The original figure has been revised to the above Supplementary Fig. 8 in SI, and the E values in the corresponding description have been updated. act Comment 1-2.8: The Ti in figure 2A does not look okay: (A) A scheme for inverse loading TiO x Response: We thank the reviewer and apologize for the display issue in the figure. Action: The original figure has been revised to Fig. 2e. In addition, Figure 1D in the original manuscript with a similar issue has been revised to Fig. 2b below. Fig. 2e Schematic of inverse loading TiO onto the M/SiO catalysts. x 2 Fig. 2b Adsorption geometry of m-cresol on M/TiO and M/SiO catalysts (M = Ni or 2 2 NiSn) Comment 1-2.9: The following phrase is ungrammatical: “To construct inverse structure” Response: We thank the reviewer for the comment. Action: The original sentence “To construct inverse structure, synthesis was conducted via slow hydrolyzation of tetrabutyl titanate to the as-prepared Ni/SiO or NiSn/SiO 2 2 catalysts” has been revised as “The inverse structure was synthesized by slow hydrolysis of tetrabutyl titanate over the as-prepared Ni/SiO or NiSn/SiO catalysts”. 2 2 Comment 1-2.10: Line 300 “semi quantified”? What is the reason not to simply quantify Ti? Response: We thank reviewer for this kind reminder. The sentence here is to show the similar Ti content on two catalysts. Based on the comment, the quantified Ti content from ICP-OES (Supplementary Table 1) is presented instead of semi-quantified results from XPS. Supplementary Table 1 Element loading measured by ICP-OES. Metal loading (wt%) Catalyst Ni Sn Ti Ni/SiO 1.98 2 NiSn/SiO 2.00 1.30 2 Ni/TiO 1.98 2 NiSn/TiO 1.99 1.27 2 0.5Ti-Ni/SiO 2.02 1.03 2 0.5Ti-NiSn/SiO 1.92 1.32 1.13 2 Action: The original sentence “the semi-quantified Ti molar content is 0.61% and 0.47% on the 0.5Ti-Ni/SiO and 0.5Ti-NiSn/SiO catalysts, respectively, as determined by X- 2 2 ray photoelectron spectroscopy (XPS)” has been replaced by “the quantified Ti content is 1.03 wt% and 1.13 wt% on the 0.5Ti-Ni/SiO and 0.5Ti-NiSn/SiO catalysts, 2 2 respectively, as determined by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES, Supplementary Table 1)”. The above Supplementary Table 1 has been added in the SI, while the corresponding description has been added in Catalyst characterization section in the revised manuscript: “The element loading of catalyst was determined by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) on Agilent ICP-OES 5110 instrument. Before the measurement, the sample digestion process began with weighing 0.1 g of the sample into a polytetrafluoroethylene digestion tube, followed by the addition of 5 mL of concentrated HNO₃ (65%) and 2-3 mL of HF (40%). Subsequently, the sealed tube underwent microwave-assisted digestion using a programmed temperature protocol: the temperature was first raised to 120 °C within 5 minutes and held for 5 minutes, then further increased to 180-200 °C within another 5 minutes and maintained at this range for 30-40 minutes to ensure complete digestion.” Comment 1-2.11: There are a lot of quantification methods that do not add much or any value to overall narrative – should be shifted to SI (e.g. Raman, XRD, EXAFS) Response: We appreciate the reviewer for the kind suggestion. Considering that Supplementary Fig. 14 contains the full Raman information, we delete the Raman spectra (Figure 3C) in the original manuscript. The XRD results are all presented in SI, and the EXAFS (Figure 3D) in the original manuscript is moved to SI. Action: The Raman spectra (Figure 3C) in the original manuscript has been deleted, and EXAFS (Figure 3D) in the original manuscript has been shifted to SI as Supplementary Fig. 16b. The corresponding figure numbers have been adjusted accordingly. The revised Fig. 4 in the main text is presented below: c e 2054 2077 u. ) Ni/SiO 2 u. ) a. 0.5Ti-Ni/SiO a. u n k ( 2075 2 u n k ( 2090 2056 M M 0.01 a - a - k 0.0002 k el el Ni/SiO u b 1940 u b 0.5Ti-N 2 i/SiO K K 2 2100 2000 1900 2200 2100 2000 1900 Wavenum ber (cm-1) Wavenum ber (cm-1) d f 2069 2066 a. u. ) 2064 a. u. ) 2064 k ( k ( n n u u M M k a - NiSn/SiO k a - NiSn/SiO b el 0.01 0.5Ti-NiS 2 n/SiO b el 0.01 0.5Ti-NiS 2 n/SiO u 2 u 2 K K 2100 2000 1900 2200 2100 2000 1900 Wavenumber (cm-1) Wavenumber (cm-1) Fig. 4 Characterization of SiO supported catalysts. HAADF and EELS mappings 2 of Ni-L edge (green), Ti-L edge (red) and Sn-M edge (purple) in a 0.5Ti-Ni/SiO and b 2 0.5Ti-NiSn/SiO samples after reduction. in-situ DRIFTS obtained after CO adsorption 2 and purge with Ar at 20 °C for 30 min over c Ni/SiO and 0.5Ti-Ni/SiO catalysts, as 2 2 well as over d NiSn/SiO and 0.5Ti-NiSn/SiO catalysts. in-situ DRIFTS obtained after 2 2 CO adsorption for 30 min over e Ni/SiO and 0.5Ti-Ni/SiO catalysts, as well as over f 2 2 NiSn/SiO and 0.5Ti-NiSn/SiO catalysts. 2 2 Comment 1-2.12: The following phrase is ungrammatical: “DFT study was conducted- should be A DFT study”. Response: We thank the reviewer for the kind reminder. Action: “DFT study was conducted” in the original manuscript has been revised to “a DFT study was conducted”. Comment 1-2.13: The following phrase is ungrammatical: “However, through the adsorption is not as strength as that on Ni(111) surface,”. Response: We thank the reviewer for the kind reminder. Action: The original sentence “However, through the adsorption is not as strength as that on Ni(111) surface, the O atom in m-cresol becomes closer to the Ni Sn(111) 3 surface” has been revised as “Despite weaker adsorption of m-cresol on Ni Sn(111) compared to Ni(111), its O atom is closer to the Ni Sn(111) surface”. 3 Comment 1-2.14: What evidence is there a Ti O cluster. is the right way to model Ti? 3 6 Response: We thank the reviewer for the kind comment. It is unlikely to achieve the uniform formation of the Ti O structure on the inverse catalysts from experiment, and 3 6 we must acknowledge the diversity of TiO species that exist. The choice of the Ti O x 3 6 cluster in our DFT model is based on the following reasons: (1) The inversely loaded TiO forms a highly dispersed structure that partially covers x the Ni or NiSn surface, evidenced by XRD, Raman, TEM and CO pulse chemisorption results. This structure is not highly crystallized nor does it form a dense, film-like structure; it is also not atomically dispersed as Ti O species. 1 x (2) The inverse catalysts are widely studied in the literature, and their structures are generally modelled as oxide clusters containing 2-4 metal atoms located on a metal surface, such as In O /Pd (J. Am. Chem. Soc. 2022, 144, 4186−4195), Fe O /Ni (Chem 2 5 3 3 2020, 6, 2703–2716), Zr O /Cu (J. Am. Chem. Soc. 2023, 145, 26350−26362), W O /Pt 3 6 3 7 (J. Am. Chem. Soc. 2024, 146, 13862−13874), and Ti O /Pd (Angew. Chem. Int. Ed. 4 x 2023, 62, e202310191). Among them, the oxide cluster containing 3 metal atoms is more commonly used (J. Am. Chem. Soc. 2023, 145, 26350−26362; Phys. Chem. Chem. Phys., 2012,14, 16626-16632). (3) For the inverse TiO -M structure, the Ti O model is widely reported (J. Phys. Chem. x 3 x C 2024, 128, 17153–17164; J. Chem. Phys. 2020, 152, 054714; Phys. Chem. Chem. Phys. 2012, 14, 16626-16632), and larger size of TiO cluster would require more x computational resources. Action: Based on the reviewer’s comment, we have added more references to support the sentence in the manuscript: “as the oxide trimer is usually used to model the relatively small oxide particles in the inverse metal oxide-metal system40-43.” The added references are: J. Phys. Chem. C 2024, 128, 17153–17164; J. Am. Chem. Soc. 2023, 145, 26350−26362; Phys. Chem. Chem. Phys. 2012, 14, 16626-16632. Comment 1-2.15: What evidence is there that O vacancies are important? Response: We thank the reviewer for the comment. The importance of O vacancies in HDO have been elucidated by a large number of studies (see reviews: ChemSusChem 2021, 14, 4377-4396; Green Chem. 2020, 22, 1072-1098; Green Chem. 2020, 22, 8140- 8168; Green Chem. 2021, 23, 9348-9376). According to these studies, the O vacancy from partially reduced TiO species is a typical active site that participates in the C-O x cleavage step. In our study, we observe that the presence of TiO significantly improves x the toluene yield, regardless of whether the TiO is introduced by the inverse loading x method or by TiO support. Meanwhile, the XPS results show the existence of Ti3+ 2 species, which indicates the formation of O vacancy. Therefore, we believe that O vacancies provided by TiO are important in this reaction. x Comment 1-2.SI.1: Need more information about composition – what phase? Particle size? “commercial TiO ” 2 Response: We thank the reviewer for the kind reminder. The commercial TiO is P25 2 from from Sigma-Aldrich (SKU no. 718467), with a primary particle size of 21 nm and a mixed phase of anatase and rutile. Action: To provide detailed information of the main chemical reagents used in this work, a Materials section has been added in Methods in the revised manuscript: “The commercial SiO support was purchased from Aladdin Scientific Corp. with S of 2 BET 200 m2/g. The commercial TiO support was purchased from Sigma-Aldrich (SKU no. 2 718467, P25 with a mixed phase of anatase and rutile, primary particle size of 21 nm, quoted S = 35-65 m2/g). Analytically pure toluene and Ni(NO ) ·6H O were BET 3 2 2 obtained from Shanghai Hushi Laboratorial Equipment Co., Ltd. Dimethyltin dichloride (98%), triethylamine (99%), ethanol (99.8%), tetrabutyl titanate (99%), m- cresol (99%), and isopropanol (99.5%) were purchased from Shanghai Macklin Biochemical Technology Co., Ltd.” And redundant descriptions that appeared in other paragraphs have been deleted. Comment 1-2.SI.2: Was this held at 580 C after ramping at this rate? “calcined in a muffle furnace at 580 °C for 3 h at a heating rate of 2 °C/min” Response: We thank the reviewer for the kind comment. The temperature is held at 580 °C for 3 h. Action: To describe clearly, the sentence has been revised as “calcined in a muffle furnace at 580 °C for 3 h (after ramping to this temperature with a heating rate of 2 °C/min)”. Similar sentences have also been revised: “calcined at 400 °C for 4 h at a heating rate of 2 °C/min” has been revised as “calcined at 400 °C for 4 h (heating rate: 2 °C/min)”; “calcination in air at 300 °C for 1 h at a heating rate of 10 °C/min” has been revised as “calcination in air at 300 °C for 1 h (heating rate: 10 °C/min)”; “reduced at 400 °C for 1 h at a heating rate of 10 °C/min” has been revised as “reduced at 400 °C for 1 h (heating rate: 10 °C/min)”. Comment 1-2.SI.3: There is not enough information on the section below. “0.20 g Ni(NO )·6H O was dissolved in a certain amount of distilled water, and drop added to 3 2 2.0 g support,” Response: We thank the reviewer for the kind reminder. The water amount used at this step is added after this sentence. Action: “The amount of distilled water used here is 4.0 g for SiO based samples, and 2 0.7 g for TiO based samples.” has been added after the mentioned sentence. 2 Comment 1-2.SI.4: There is insufficient detail in the section below. Need to know amounts of everything. “Synthesis of inverse TiO -Ni/SiO and TiO -NiSn/SiO x 2 x 2 catalysts: Tetrabutyl titanate was used as the TiO precursor. As the tetrabutyl titanate x was easy to be hydrolyzed, we firstly dissolved tetrabutyl titanate in ethanol, and then drop added to the as-prepared Ni/SiO or NiSn/SiO catalysts and impregnation 2 2 overnight. While exposing to the air, the H O in air would make tetrabutyl titanate be 2 slowly hydrolyzed and deposited as TiO . The carbon ligand was removed by x calcination in air at 300 °C for 1 h at a heating rate of 10 °C/min. The catalyst was named as xTi-M/SiO (M=Ni or NiSn), where x refers to the nominal molar ratio of Ti 2 to Ni.” Response: We thank the reviewer for the kind reminder. The amounts of chemical agents used in this preparation process are added. Action: Based on the comment, the sentence “we firstly dissolved tetrabutyl titanate in ethanol, and then drop added to the as-prepared Ni/SiO or NiSn/SiO catalysts and 2 2 impregnation overnight.” has been revised as “we firstly dissolved a calculated amount of tetrabutyl titanate into 4.0 g of ethanol, and then dropped the resulting solution to 2.0 g of as-prepared Ni/SiO or NiSn/SiO catalyst and impregnated overnight. Here the 2 2 tetrabutyl titanate amount is 0.116 g when Ti/Ni molar ratio is 0.5.” Comment 1-2.SI.5: The meaning of the phrase below is unclear. “The catalyst was reduced at 400 °C in H for 1 h before reaction if there are no additional notes.” 2 Response: We thank the reviewer for the kind comment. Considering that the reduction pretreatment has been described in activity test and catalyst characterization that needed catalyst reduction, we delete this sentence here. Action: The mentioned sentence has been deleted. Comment 1-2.SI.6: How was the reactant vaporized? “and vaporized before entering the reactor.” Response: We thank the reviewer for the comment. The reactant is vaporized under H 2 flow at 205 °C before entering the reactor. Action: The sentence has been revised to provide a clearer description: “and vaporized under H flow at 205 °C before entering the reactor”. 2 Comment 1-2.SI.7: What does this mean? “To consider the computation accuracy and cost comprehensively,” Response: We thank the reviewer for the comment. The phrase here is intended to succinctly describe the trade-off we made, but we agree that a more detailed explanation is necessary. The primary reason for selecting a 2×2×1 k-point grid is the large size of our computational model. After considering the size of NiSn alloy, TiO cluster and m- x cresol molecule, we decide to construct a 6×6 periodic model comprising over 130 atoms. For systems of this scale, the computational cost for structural optimization and frequency calculations increases dramatically with k-point density. Our choice is guided by the following specific considerations: (1) System size and k-point sensitivity: Large supercells have a small Brillouin zone. Consequently, a relatively sparse k-point mesh is often sufficient to achieve convergence for relative energies (e.g., adsorption energies, reaction barriers), which are the key properties reported in our study. The absolute total energy is indeed sensitive to k-points, but the differences in total energy between similar configurations (which determine relative energies) converge much faster. (2) Convergence testing for relative energies: To ensure reliability, we compared the adsorption energy of m-cresol using a 2×2×1 grid versus a more computationally expensive 3×3×1 grid. The difference was found to be less than 0.05 eV, which is negligible for the comparative and mechanistic conclusions of our study. Increasing the grid beyond 2×2×1 would thus provide little improvement in accuracy for relative energies at a higher computational cost. Additionally, for ZPE corrections, we fixed all substrate atoms and only computed the vibrations of the adsorbate species. This is a standard practice to obtain accurate vibrational modes related to the surface reaction while conserving computational resources. Action: The mentioned vague phrase has been revised to a more precise description: “A Monkhorst-Pack grid of 2×2×1 was used to sample the surface Brillouin zone, which was deemed appropriate for k-point convergence given the large size of the supercell (>130 atoms).” And the mistaken phrase “a 4×4 unit cell” has been revised to “a 6×6 unit cell”. Comment 1-2.SI.8: Where does the “ΔZPE is the correction in zero-point energies” come from? Response: We thank the reviewer for the comment. In our study, the ΔZPE values are computed directly from vibrational frequency calculations performed on all optimized structures. Action: The original term “where ΔE is obtained from DFT calculations, ΔZPE is the correction in zero-point energies” has been revised to a more precise description: “where ΔE is the difference in DFT electronic energies, ΔZPE is the correction in zero- point energies obtained from vibrational frequency calculations performed on all optimized structures”. Comment 1-2.SI.9: What are the values for entropy? What is the justification for ignoring entropy everywhere else? Response: We thank the reviewer for this valuable comment. We agree that a more rigorous treatment of entropy is important for accuracy. In the original manuscript, we employed a simplified approach for computational efficiency and clarity in trend analysis: “The entropy of adsorbed species is considered as 0 except for the vertically adsorbed m-cresol. The entropy of adsorbed m-cresol on Ni Sn(111) is simplified as 3 about 2/3 of the gaseous m-cresol as only vertical translational degree of freedom is limited.” Following the reviewer’s comment, we have now performed a more rigorous and detailed analysis in the revised manuscript: (1) Calculated the vibrational entropy for all adsorbed species from their vibrational frequencies obtained through DFT calculations; (2) Re-calculated all free energies using these computed entropy values. Fig. R1 Comparison between the a original and b re-calculated results of the optimized energy for m-cresol adsorption (E ), the activation energy (E ) and the ad act reaction energy (E ) for C-O cleavage over different surface. rxn The original and updated results are compared in Fig. R1. The re-calculated values of E and E are similar to the original values, while the E values show obvious act rxn ad differences, demonstrating a strong influence of –TΔS term on E . Especially, the E ad ad on Ni Sn(111) is a positive value, indicating the weak m-cresol adsorption on this 3 surface at high temperature (a trend of low surface coverage). Similar results are also found in DFT calculated CO adsorption energy (Nat. Mater. 2025, 24, 891–899; Angew. 2 Chem. Int. Ed. 2025, 64, e202422953). Despite this, the key qualitative trends of E , ad E and E across different catalytic models, which related to the central conclusion act rxn of our study, remain consistent with the initial findings. Action: Based on the reviewer’s comment, the sentence “The entropy of adsorbed species is considered as 0 except for the vertically adsorbed m-cresol. The entropy of adsorbed m-cresol on Ni Sn(111) is simplified as about 2/3 of the gaseous m-cresol as 3 only vertical translational degree of freedom is limited.” in DFT calculation section has been revised to “The entropy of adsorbed species is calculated within the harmonic approximation using the vibrational frequencies obtained from the optimized structure.” And the Fig. 5E in the original manuscript has been revised to the above Fig. R1b and moved to SI as Supplementary Fig. 25. In the manuscript, the energy values have been revised to the re-calculated results: “0.80 eV and 0.84 eV were obtained” has been revised to “0.88 eV and 0.84 eV were obtained”, “though the adsorption energy is calculated to be high as -2.05 eV, such adsorption mode on Ni(111) leads to high energy barrier of 1.50 eV and a reaction energy of 0.60 eV (endothermic) for C-O cleavage” has been revised to “though the entropy-corrected adsorption energy is calculated to be high as -0.81 eV, such adsorption mode on Ni(111) leads to high energy barrier of 1.44 eV and a reaction energy of 0.53 eV (endothermic) for C-O cleavage”, “, leading a weak adsorption energy of -0.91 eV” has been revised to “with positive adsorption energy”, “the C-O cleavage barrier is decreased to 1.01 eV with a reaction energy of -0.1 eV (slightly exothermic)” has been revised to “the C-O cleavage barrier is decreased to 0.83 eV with a reaction energy of -0.13 eV (slightly exothermic)”, “a strong adsorption energy of - 2.42 eV” has been revised to “a strong adsorption energy of -1.24 eV”, “a moderate energy barrier of 1.20 eV with a reaction energy of -0.53 eV (exothermic)” has been revised to “a moderate energy barrier of 0.93 eV with a reaction energy of -0.81 eV (exothermic)”, “a moderate adsorption energy of -1.26 eV” has been revised to “a moderate adsorption energy of -0.22 eV”, “further lowered to 0.75 eV” has been revised to “further lowered to 0.68 eV”, “a reaction energy of -1.2 eV” has been revised to “a reaction energy of -1.10 eV”. Comment 1-2.SI.10: Figure S1. XRD patterns of different catalysts. The catalysts were pre-reduced at 400 °C for 1 h. What is the green highlight for? Response: We thank the reviewer for the comment. The green region highlights the broad diffraction peak of NiSn alloy. We redraw the figure to present the results more clearly. ★Rutile  Anatase   O2 ★   S n/ Ti  Ni   u. ) ★ ★ ★ ★ a. ( y sit Ni/TiO n NiSn alloy 2 e nt i Ni(111) NiSn/SiO 2 Ni/SiO 2 30 40 50 60 70 2θ () Supplementary Fig. 1 XRD patterns of different catalysts. Action: The original figure has been revised to the above Supplementary Fig. 1. Comment 1-2.SI.11: Figure S9. H -TPR profiles over different catalysts – explain 2 arrows in caption, label peak maxima. Response: We thank the reviewer for the kind suggestion. The arrows are explained after the figure caption: “The two arrows show that Sn addition increases the reduction temperature in the SiO supported catalyst but decreases it in the TiO supported 2 2 catalyst.” The revised figure, with peak maxima labeled, is shown below. 275 ) u. a. 360 ( n NiSn/TiO o 2 pti 410 m Ni/TiO s u 336 2 n c o NiSn/SiO 2 2 H Ni/SiO 2 100 200 300 400 500 600 700 T (C) Supplementary Fig. 10 H -TPR profiles over different catalysts. The two arrows 2 show that Sn addition increases the reduction temperature in the SiO supported 2 catalyst but decreases it in the TiO supported catalyst. 2 Action: The original figure has been revised to the above Supplementary Fig. 10. Comment 1-3: More detail is also needed on number of replicates and error propagation needs to be clearly articulated and error bars included on all catalytic data. Response: We thank the reviewer for the important suggestion. We performed two more replicate catalytic tests, and confirmed that all data showed good reproducibility. The average values calculated from the three replicate tests are used in catalytic performance figures, and standard deviation error bars are also included. Action: The original Fig. 1(A) and Fig. 2(B) have been replaced by the following Fig. 2a and Fig. 2f, respectively. And the description “The error bars show the standard deviation of conversions based on three repeated experiments.” has been added in the figure caption. a 20 b Conversion OH % ) OH ( 15 d CH + el Yi DMB Ben 10 / n Ph CH 4 o Tol i s r 5 e v n o C 0 N N N N i/S iO i/T iO iS n /S iS n /T iO iO 2 2 2 2 c 100 d Fig. 2a m-Cresol conversion and product distribution on different catalysts. Tol = Toluene, CH = Metha8n0e, Ph = Phenol, Ben = BenzenNe, iDSMn/BS i=O Dimethyl biphenyl (a 4 ) 2 deoxygenation product). Reaction conditions: T = 350 °C, P = 1 atm, W/F = 0.3 h, TOS 60 = 20 min. n Ni/SiO o 2 i s e r 40 v n Ni/TiO o C 20 2 0 0 50 100 150 200 250 300 350 TOS (min) f g e 100 15 Conversion ) % DMB ( Ben % ) 80 0.5Ti-NiSn/SiO d 2 Yi el 10 P C h H o n ( 60 4 i / n Tol r s o e 40 v s i 5 n 0.5Ti-Ni/SiO r o 2 e C 20 v n o C 0 0 N i/S iO 2 0 .5 T i-N i 1 /S T i i O -Ni/S N iO iS 2 n /S 0 i . O 5 2 T i-N 1 iS T n i- / N S i i S O n /S iO 0 50 100 T 1 O 5 S 0 2 (m 00 in 2 ) 50 300 350 2 2 2 100 80 60 40 20 0 0 50 100 150 200 250 300 350 f 15 Conversion DMB ) Ben % Ph ( d CH el 10 4 Tol Yi / n o si r e 5 v n o C 0 N i/S iO 2 0.5T i-N i/S iO 1T i-N i/S iO 2 N iS n/S iO 2 0.5T i-N iS n/ 1 S T iO i-N iS n/S iO 2 2 2 Fig. 2f m-Cresol conversion and product distribution on inverse Ti-M/SiO catalysts. 2 Reaction conditions: T = 350 °C, P = 1 atm, W/F = 0.3 h, TOS = 20 min. The original Fig. 1(E) has been replaced by the following Supplementary Fig. 8, with the description “The error bars show the standard deviation of Ln(r ) based on three Tol repeated experiments” in the figure caption: 2.0 NiSn/TiO 2 1.5 E = 65.8 4.5 kJ/mol act ) R2= 0.98 h 1.0 / at gc ol/ 0.5 m m ol 0.0 T r NiSn/SiO n ( 2 L -0.5 E = 86.2 8.3 kJ/mol act R2= 0.99 -1.0 1.60 1.65 1.70 1.75 1000/T (K-1) Supplementary Fig. 8 Arrhenius plots of m-cresol deoxygenation to toluene on NiSn/SiO and NiSn/TiO catalysts. Reaction conditions: P = 1 atm, H /m-cresol = 60, 2 2 2 TOS = 20 min, conversion was kept under 10% by adjusting the W/F. The error bars show the standard deviation of Ln(r ) based on three repeated experiments. Tol All the related data described in the manuscript have been updated. Comment 1-4: The structure of the manuscript undercuts its potential impact. The whole idea of spending 12 pages discussing the first generation catalyst only to then switch to a second generation catalyst does not seem like an efficient or effective way to present this information. The paper would be more impactful if it begins with what works best and perhaps the discussion of the first generation catalyst can be mentioned briefly and mostly moved to SI. Response: We sincerely appreciate the reviewer’s insightful comment and suggestion. Accordingly, we revise the manuscript structure by merging the content on first- and second-generation catalysts into a single section titled “Boosting HDO performance and stability on inverse TiO -NiSn interface”. The detailed structural characterization x analysis for the first-generation catalysts is moved to SI. The original Fig. 1C (DRIFTS of m-cresol adsorption), Fig. 1E (Arrhenius plots of m-cresol deoxygenation to toluene), and Fig. 1F (H -D TPSR) is moved to SI, while a new schematic of coking behavior 2 2 on different active sites is added. In the revised section, we first analyze the performance and stability of the first- generation catalysts briefly, highlighting the importance of TiO species and NiSn alloy x in m-cresol activation and coking resistance, respectively (revised Fig. 2a-d). Then, based on these findings, we design the second-generation catalyst with an inverse TiO - x NiSn interfacial structure, which boosts the HDO performance and stability (Fig. 2e-g). Through the above revision, the original 6-page discussion of the first-generation catalysts in the Results section is condensed to 3 pages, while the design logic behind the inverse TiO -NiSn interfacial structure is illustrated. x Action: The content on first- and second-generation catalysts has been merged into a single section titled “Boosting HDO performance and stability on inverse TiO -NiSn x interface”, with the revised Fig. 2 and text shown below: a 20 b OH Conversion % ) OH ( 15 el d CH4 + / Yi DMB Ben 10 / n Ph CH 4 o Tol i s r 5 e v n o C 0 Ni/SiO 2 Ni/TiO 2 NiSn/SiO NiSn/TiO 2 2 c 100 d 80 NiSn/SiO ) 2 % NiSn/TiO ( 2 o n 60 Ni/SiO si 2 e r 40 v n Ni/TiO C o 20 2 0 0 50 100 150 200 250 300 350 TOS (min) e f g 100 ) 15 Conversion % DMB Yi el d ( 10 Ben P C h H o n ( % ) 6 8 0 0 0.5Ti-NiSn/SiO 2 / si o n 5 Tol 4 n v e r si 40 0.5Ti-Ni/SiO v e r C o 20 2 n o C 0 0 Ni/SiO 2 0.5Ti-Ni 1 /S T i i O -Ni/S N iO iS 2 n/S 0 i . O 5 2 Ti-N 1 iS T n i- / N S i i S O n/SiO 0 50 100 T 1 O 5 S 0 2 (m 00 in 2 ) 50300350 2 2 2 Fig. 2 Advantage of the inverse TiO -NiSn interface over other catalytic structures x for m-cresol HDO. a m-Cresol conversion and product distribution on different catalysts. Tol = Toluene, CH = Methane, Ph = Phenol, Ben = Benzene, DMB = 4 Dimethyl biphenyl (a deoxygenation product). Reaction conditions: T = 350 °C, P = 1 atm, W/F = 0.3 h, TOS = 20 min. b Adsorption geometry of M/TiO and 2 M/SiO catalysts (M = Ni or NiSn). c m-Cresol conversion as a function of TOS. 2 Reaction conditions: T = 350 °C, P = 1 atm, W/F was adjusted to achieve a similar initial conversion. d Schematic of coking behavior on different active sites. e Schematic of inverse loading TiO onto the M/SiO catalysts. f m-Cresol conversion and product x 2 distribution on inverse Ti-M/SiO catalysts. Reaction conditions: T = 350 °C, P = 1 atm, 100 2 W/F = 0.3 h, TOS = 20 min. g Stability of inverse Ti-M/SiO catalysts. Reaction 2 conditions: T = 350 °C, P = 1 atm, W/F was adjusted to achieve a similar initial conversion. The error bars show the standard deviation of conversions based on three repeated experiments. 80 60 40 20 0 0 50 100 150 200 250 300 350 “Firstly, the interfacial effect on m-cresol HDO performance over Ni based catalysts were investigated. Catalysts with 2 wt.% Ni loading on SiO and TiO were synthesized 2 2 by incipient wetness impregnation method and compared to NiSn bimetallic catalysts with the same Ni loading. Here SiO was selected as an inert support, where HDO is 2 expected to occur solely over the metal/bimetallic surface. In contrast, TiO was chosen 2 as an active support where Ti cations at the metal-support interface can participate in the reaction. The basic element loading, crystalline and morphological characterizations of these catalysts are presented in Supplementary Table 1, Supplementary Figs. 1-5 and Supplementary Note 1. The gas-phase conversion of m-cresol was studied in a fixed- bed reactor at temperature of 350 °C under atmospheric H pressure. As expect20, C-C 2 hydrogenolysis to CH and phenol predominantly occurred over deoxygenation to 4 toluene on the mono Ni active sites, leading to poor deoxygenation selectivity of Ni/SiO catalyst (Fig. 2a). Ni particles supported on TiO exhibited lower overall 2 2 activity but enhanced yield and selectivity toward toluene compared to those supported on SiO . Previous studies have shown that this trend in reactivity is the result of strong 2 metal-support interaction (SMSI) between Ni and TiO , where reduced TiO species 2 x migrated to Ni surface during reduction process25. It prevents sintering of Ni particles, evidenced by their smaller size on TiO . In addition, the formation of Ni-TiO interfaces 2 x lowers the energy barrier, thereby enhancing deoxygenation activity26. Furthermore, partial surface coverage by TiO species decreases the number of exposed Ni sites, x suppressing the structure-sensitive C-C hydrogenolysis side reaction27 and consequently reducing the overall conversion of m- cresol. The performance of supported NiSn alloy catalysts is also shown in Fig. 2a. First of all, unlike pure Ni phase that mainly catalyzes C-C hydrogenolysis, the catalysts containing NiSn alloy active phase are highly selective for deoxygenation reaction, even at all conversion levels (Supplementary Fig. 6). This can be attributed to the geometric isolation effect of Sn which suppresses the structure sensitive C-C hydrogenolysis side reaction. Secondly, comparison between Ni/SiO and NiSn/SiO shows that alloying Ni 2 2 with Sn reduces the total activity but enhances the toluene yield. Similar to the finding in furfural HDO, the Sn atoms on surface not only occupy the Ni active centers, but also modify their chemical nature, thereby enhancing the activity of Ni in the target deoxygenation reaction21,28. Thirdly, it is interestingly to note that the use of TiO 2 support reverses the activity trend between Ni and NiSn sites. The NiSn/TiO catalyst 2 shows three times higher m-cresol conversion than that of Ni/TiO (Fig. 2a). Last but 2 not least, in contrast to monometallic Ni phase on TiO , which deters m-cresol 2 conversion relative to Ni/SiO , the NiSn alloy on TiO shows almost three times higher 2 2 m-cresol conversion than that on SiO . 2 Subsequently, m-Cresol and H probe characterizations were investigated to elucidate 2 the adsorption and activation of reactants on the active site, which are key factors determining reactivity (Supplementary Fig. 7-9 and Supplementary Discussion 1). In- situ m-cresol adsorption diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) in Supplementary Fig. 7 demonstrates the donor-acceptor interaction between oxygen atom of m-cresol and Lewis acid sites on TiO , which is stronger than 2 the H-bonding interaction between m-cresol and SiO support13,14. Combined with 2 previous DFT studies, the adsorption configurations of m-cresol on metal surface and metal-TiO interface are shown in Fig. 2b. m-Cresol binds to metal sites through phenyl 2 ring with the hydroxyl group (-OH) tilting away from surface, while the TiO at the x neighbor of metal sites can interact with the O atom in -OH group26. Such adsorption configuration at the interface site facilities the effective activation of C-O bond in m- cresol, thus resulting in lower energy barrier for deoxygenation reaction (Supplementary Fig. 8). For H activation, the hydrogen-deuterium temperature- 2 programed surface reaction (H -D TPSR) indicates that the addition of Sn to Ni/SiO 2 2 2 significantly prevents H dissociation (Supplementary Fig. 9), consistent with previous 2 studies and DFT calculation which showed an enhanced energy barrier for H 2 dissociation on the NiSn alloy surface compared to the pure Ni surface21,28. Fortunately, this drawback can be mitigated through the formation of NiSn-TiO interface, which is x also supported by TPR results (Supplementary Fig. 10). All these findings underscore the crucial role of both TiO and Sn, as well as their synergistic effect in modulating the x chemical nature at the interface site, thus leading to enhanced phenolic HDO performance. The catalytic stability and the oxygen temperature programed oxidation (O -TPO) 2 profile of spent catalysts are further evaluated and shown in Fig. 2c and Supplementary Fig. 11. The Ni/TiO deactivates at a significantly higher rate as compared to Ni/SiO . 2 2 Correspondingly, the total coke deposition on Ni/TiO is two times higher than that on 2 Ni/SiO (Supplementary Table 2). This can be ascribed to the acidic nature of TiO 2 2 support (Supplementary Fig. 12 and Supplementary Table 3), which promotes condensation of m-cresol, leading to increased coke formation29. As expected, the introduction of Sn enhances HDO stability on both SiO and TiO supported Ni 2 2 catalysts. Therefore, the coking behavior of catalysts in m-cresol HDO can be illustrated. As shown in Fig. 2d, coke formation occurs at two types of active sites: metallic Ni sites and TiO acid sites. Metal induced coking can be suppressed through the formation of NiSn alloy, while acid induced coking can be mitigated by replacing the acidic TiO 2 support with inert SiO . 2 The NiSn/SiO exhibits the highest anti-coking stability, but its activity remains poor 2 in the absence of TiO support. Considering that only the oxophilic TiO species 2 x adjacent to the NiSn alloy contribute to the synergetic activation of m-cresol, while excess acidic sites on TiO exacerbate coking, we sought to explore whether a catalyst 2 composed of trace TiO on NiSn particles could achieve a new level of catalyst x performance. The inverse structure was synthesized by slow hydrolysis of tetrabutyl titanate over the as-prepared Ni/SiO or NiSn/SiO catalysts, as presented in Fig. 2e. 2 2 The obtained catalyst was named as xTi-M/SiO (M = Ni or NiSn), where x refers to 2 the nominal molar ratio of Ti to Ni. O -TPO analysis of the fresh catalysts indicates that 2 the carbonaceous species from tetrabutyl titanate are almost removed (Supplementary Fig. 13 and Supplementary Table 4). The activity comparison among these catalysts is shown in Fig. 2f. Specifically, over Ni/SiO , the inverse loading of TiO caused a 2 x decrease in total conversion but an enhanced yield to toluene. This was consistent with the activity trend between Ni/SiO and Ni/TiO , and could also be attributed to the 2 2 SMSI effect between TiO and Ni nanoparticles. As expected, more TiO on Ni/SiO x x 2 leaded to further inhibition in reactivity. Conversely, the decoration of TiO on x NiSn/SiO significantly enhanced the deoxygenation reaction, with the m-cresol 2 conversion and toluene yield increased by almost 2.7 times. Notably, its activity was comparable with that of the NiSn/TiO catalyst. More interestingly, the 0.5Ti- 2 NiSn/SiO catalyst exhibited greater stability (Fig. 2g), with less coke accumulation as 2 indicated by O -TPO (Supplementary Fig. 13). Combined with NH temperature- 2 programmed desorption (NH -TPD) results in Supplementary Fig. 12, it demonstrates 3 3 that the inverse TiO loading outperforms conventional TiO support in suppressing x 2 acid induced coking.” In addition, to streamline the main text, the transitional paragraph “The Sn alloyed Ni catalyst has been previously… than Ni/SiO catalyst with monometallic active center.” 2 in the original manuscript has been deleted; The basic characterization analysis of the first-generation catalysts in Supplementary Fig. 1-5 has been moved to SI as Supplementary Note 1, and the detail discussion of m-cresol and H activation has been 2 moved to SI as Supplementary discussion 1 (not attached here for simplification). …………………………end of response to Reviewer 1………………………… Reviewer 2 Comment: In this manuscript, the authors study TiO -functionalized, bimetallic 2 catalysts for hydrodeoxygenation of m-cresol, which is a much-studied reaction. This work essentially combines two ideas that have been in the literature for a while: adding Sn to Ni to reduce the tendency toward coke formation, and using TiO modifiers on 2 the surface of the catalyst to improve interfacial activity. The authors discover some interesting synergistic effects. For example, whereas TiO -supported Ni Sn catalysts 2 3 are active but not especially stable, producing inverse catalysts in which the TiO is 2 located above the catalyst particles produces an active and stable catalyst. The authors largely do an excellent job of characterizing the prepared materials and analyzing the key reaction process with computational methods. Although some of the basic concepts that motivated the paper have been well-established, for me there is clearly sufficient novelty in the results to justify publication in Nature Comm. I recommend that the authors consider the following few points as they revise their manuscript. Response: We appreciate the reviewer for the positive assessment of our work and the constructive suggestions. The point-by-point responses to these suggestions are presented below. Comment 2-1: Regarding Figure 1C, did the authors perform a control in which DRIFTS was done after adsorption of cresol on the support only? Sometimes it can be difficult to use DRIFTS to probe interfacial sites specifically, and some of these compounds may adsorb on support sites far from the interface. Response: We thank the reviewer for this insightful comment and suggestion. We have performed the DRIFTS study of m-cresol adsorption on the SiO and TiO supports, 2 2 and found that the results are the same with that on the corresponding supported catalysts (Supplementary Fig. 7). This control experiment confirms the reviewer’s concern that m-cresol adsorption on interfacial sites is difficult to observe using DRIFTS. It is consistent with the report from Popov et al. (J. Phys. Chem. C 2010, 114, 15661) that the phenolic -OH group is easy to interact with acid sites or defects on supports (such as the strained siloxane bridges on SiO ), and then forms phenate or 2 phenoxy species. Even on the SiO support, these surface species remain stable, making 2 it difficult to observe m-cresol adsorption on interface sites. Despite this, the redshift in the characteristic bands of m-cresol adsorption on TiO , 2 compared to those on SiO , indicates a donor-acceptor interaction between m-cresol 2 and TiO support. This interaction is stronger than the H-bonding interaction on SiO 2 2 support (J. Phys. Chem. C 2010, 114, 15661；ACS Catal. 2016, 6, 1292). Therefore, we could expect the advance of metal-TiO interface on m-cresol adsorption and x activation compared to metal-SiO interface, which is consistent with the catalytic 2 performance observation here and previous experimental and DFT studies. δ(OH) 1483 3039 ν(CC ) ν(CH ) ring ring 2922 ν(CH 3 ) 1597 1578 δ(CH) u . ) 3061 2866 3 . 1431 a ( NiSn/TiO e 2 δ(OH) c Ni/TiO n 2 a b TiO r 2 o s b A NiSn/SiO 2 Ni/SiO 2 2930 2872 SiO 1588 2 1607 1489 1441 1380 3200 3000 2800 2600 1600 1400 Wavenumber (cm-1) Supplementary Fig. 7 DRIFTS of m-cresol adsorption on catalysts and supports at 200 °C. Action: Following the reviewer’s suggestion, the original DRIFTS has been revised to the above Supplementary Fig. 7 in SI, and the corresponding discussion has been revised based on the control experiment results (see Supplementary Discussion 1). “For comparison, the control experiment on supports were also performed” has been added after the second sentence of the DRIFTS discussion paragraph; “the SiO supported 2 catalysts (Ni/SiO and NiSn/SiO )” has been revised to “the SiO based samples (SiO , 2 2 2 2 Ni/SiO and NiSn/SiO )”; “demonstrating a stronger adsorption and activation of m- 2 2 cresol on the Ni/NiSn-TiO interfacial sites compared to the pure metal/alloy surfaces” 2 has been revised to “demonstrating a stronger adsorption and activation of m-cresol on TiO through the donor−acceptor interaction with the surface Lewis acid site1,3”, and 2 more discussion follows below: “Considering that the spectra of m-cresol adsorption on SiO and TiO supports is the same with that on the corresponding catalysts, it must 2 2 be noted that the information of DRIFTS here is related to the m-cresol adsorption on support rather than metal-support interface. Popov et al. investigated the adsorption of phenolic molecules on various oxide supports by infrared spectroscopy, and found that the phenol’s OH group is easy to interact with surface defects (such as strained siloxane bridges on SiO ) or acid sites, then form phenate or phenoxy species. These species 2 show strong IR bands and are very stable even on the relatively inert SiO support1, 2 making it difficult for us to observe the adsorption state of m-cresol at the interface. Despite this, the redshift of IR bands over TiO based sample demonstrates that the 2 donor-acceptor interaction between oxygen atom of m-cresol and Lewis acid site exists on TiO , which is stronger than the H-bonding interaction between m-cresol and SiO 2 2 support1. Thus, one could expect the advance of metal-TiO interface on m-cresol x adsorption and activation compared to metal-SiO interface.” 2 Comment 2-2: The authors claim that the inverse strategy is beneficial because the TiO on the surface has a lower acidity, allowing improved lifetime. However, I did not x see where this proposal was tested experimentally. Can the authors elaborate on the evidence that supports their proposal? An alternative proposal is that TiO could block 2 sites that ultimately lead to coking. I understand why the authors proposed that surface acidity is the driving factor, but the manuscript would be improved by describing the evidence for this proposal. Response: We thank the reviewer for the nice suggestion. We have conducted NH - 3 TPD characterization of these catalysts to provide further evidence. As shown in Supplementary Fig. 12 and Supplementary Table 3, Ni/SiO and NiSn/SiO present 2 2 weak acid sites, with NH desorption peak at 91-93 °C. In contrast, medium and strong 3 acid sites emerge on TiO supported catalysts, with the corresponding NH desorption 2 3 peak at 172-175 °C and 277-300 °C. For the inverse 0.5Ti-Ni/SiO and 0.5Ti-NiSn/SiO 2 2 catalysts, the strong acid sites have almost disappeared compared to TiO supported 2 catalysts, demonstrating the advantage of inverse loading of TiO in reducing surface x acidity. Weak Medium Strong Weak Medium Strong 100 172 300 100 175 277 NiSn/TiO Ni/TiO 2 2 94 96 u. ) 1 1 a. ( 6 = 1 93 0.5Ti-Ni/SiO 2 0.5Ti-NiSn/SiO 2 z 91 m/ Ni/SiO NiSn/SiO 2 2 100 200 300 400 500 100 200 300 400 500 T (C) T (C) Supplementary Fig. 12 NH -TPD curves of reduced catalysts. 3 Supplementary Table 3 Quantitative results of acidity from Supplementary Fig. 12. Acid density (μmol/g) Catalyst Weak Medium Strong Ni/SiO 11.78 0 0 2 NiSn/SiO 8.35 0 0 2 0.5Ti-Ni/SiO 12.49 6.77 0 2 0.5Ti-NiSn/SiO 9.67 8.53 0 2 Ni/TiO 4.48 9.76 13.63 2 NiSn/TiO 3.69 7.47 7.91 2 Action: Following the reviewer’s suggestion, the above Supplementary Fig. 12 and Supplementary Table 3 has been added in SI, with the following description: “As shown in Supplementary Fig. 12, Ni/SiO and NiSn/SiO present weak acid sites, with NH 2 2 3 desorption peak at 91-93 °C. In contrast, medium and strong acid sites emerge on TiO 2 supported catalysts, with the corresponding NH desorption peak at 172-175 °C and 3 277-300 °C. For the inverse 0.5Ti-Ni/SiO and 0.5Ti-NiSn/SiO catalysts, the strong 2 2 acid sites have almost disappeared compared to TiO supported catalysts, 2 demonstrating the advantage of inverse loading of TiO in reducing surface acidity.” x In addition, in the manuscript, “This can be ascribed to the acidic nature of TiO 2 support,” has been revised to “This can be ascribed to the acidic nature of TiO support 2 (Supplementary Fig. 12 and Supplementary Table 3)”; The sentence “Combined with NH temperature-programmed desorption (NH -TPD) results in Supplementary Fig. 12, 3 3 it demonstrates that the inverse TiO loading outperforms conventional TiO support in x 2 suppressing acid induced coking.” has been added after “indicated by O -TPO 2 (Supplementary Fig. 13).” The NH -TPD process has been added to the catalyst 3 characterization section: “NH -TPD characterization was conducted on the 3 Micromeritics AutoChem 2950 HP instrument equipped with a MS detector. The catalyst was firstly reduced in H at 400 °C for 1 h, followed by He purging for 0.5 h. 2 After cooling to 50 °C, 10% NH /He was introduced to the system with the adsorption 3 for 0.5 h. Then the physically adsorbed NH was purged with He again for 0.5 h. The 3 sample was heated to 600 °C at a rate of 10 °C/min. The desorption of NH is recorded 3 with m/z = 16 in order to exclude the influence of H O.” 2 Comment 2-3: Since the TiO clusters appear from experimental data to bind to 2 undercoordinated sites on the catalyst surface, did the DFT studies consider use of a stepped surface rather than a (111) surface for any exploratory calculations? Even if not, could the authors comment on whether the (111) surface would be expected to serve as a useful model? Response: We sincerely thank the reviewer for this insightful and valuable point. The suggestion to consider stepped surface models would provide a more realistic representation of the undercoordinated sites based on CO-DRIFTS evidence, but modeling a sufficiently large stepped surface to reliably host the TiO cluster and x reactants requires much more than one hundred atoms and excessive computational resources for DFT calculations. Within the scope of this work, we are confident that the (111) surface models are suitable for two key reasons: (1) The primary objective of our DFT investigation is to reveal the catalytic advantage of the inverse TiO -M interface, as compared to simple M (Ni/NiSn) surfaces. x Furthermore, we sought to compare how this inverse interface function is modulated by the choice of the underlying substrate (Ni vs. NiSn alloy). We believe that the essential catalytic advantage of the inverse TiO -M interface over simple M surface is x inherent and consistent, whether it is formed on a flat terrace or a step surface. Our models capture this core functionality. (2) The critical validation of our model lies in its ability to reproduce experimental trends. The calculated adsorption and activation energies across the four representative systems (Ni, NiSn, TiO /Ni, and TiO /NiSn) show a consistent trend with the adsorption x x properties and catalytic performances observed in our experimental catalysts. This strong correlation supports that the (111) models are suitable in elucidate the advantage of the inverse TiO -NiSn interface in this work. x Action: Based on the reviewer’s comment, the following description has been added to the second paragraph of DFT calculation section to explain our choice of the (111) surface models: “The primary objective of DFT study is to compare the catalytic function of these inverse interfaces against pure Ni and NiSn surfaces, and to identify the core functionality provided by TiO and Sn species in m-cresol HDO reaction. x While the location of TiO cluster on low-coordinated metal surface, such as step sites, x is evidenced by CO-DRIFTS results, the choice of (111) surface models here provides a well-defined benchmark system for investigating the above objective.” Comment 2-4: Although the mechanistic proposal from the DFT calculations seems similar to that from Janik and coworkers (https://doi.org/10.1016/j.jcat.2019.07.012), the authors may want to comment more on the subsequent steps of the catalytic cycle, as in the prior work. It is not so surprising that a reduced Ti O cluster will interact 3 5 strongly with the O atom of m-cresol, especially on a Sn-doped surface where the interaction of the cluster with the surface is weaker. The key step on such a surface may be regeneration of the oxygen vacancy, which is only briefly discussed here in reference Figure S17. It wasn’t so clear to me: did the authors compute the activation barrier for oxygen vacancy creation? It appears that the energy required to create such a vacancy was similar for the Ni and Ni Sn surfaces, which I find somewhat surprising given the 3 other effects of Sn. In any case, I think the authors should talk more about the full cycle. Response: We thank the reviewer for the important suggestion. We have further calculated the full catalysis cycle, including the C-O cleavage of m-cresol, the hydrogenation of m-methylphenyl fragment (C H *) and the regeneration of the oxygen 7 7 vacancy. Fig. 5 DFT studies of m-cresol HDO on different catalysts. a Optimized structures of m-cresol adsorption on Ni(111), Ni Sn(111), Ti O /Ni(111) and Ti O /Ni Sn(111) 3 3 5 3 5 3 surfaces. The Ni, Sn, Ti, O, H, and C atoms are in blue, cyan, light gray, red, white, and gray, respectively. b Schematic illustration of m-cresol HDO on Ti O /Ni Sn(111) with 3 5 3 optimized structures. c Potential energy profiles of m-cresol HDO on Ti O /Ni(111) and 3 5 Ti O /Ni Sn(111) surfaces. The inset shows potential energy profiles of the 3 5 3 regeneration of the oxygen vacancy. Supplementary Fig. 21 Schematic illustration of m-cresol HDO on Ti O /Ni(111) 3 5 surface with optimized structures. 2.0 Ni(111) NiSn(111) 1.5 3 1.22 1.0 (0.83) 0.63 ) 0.5 0.39 V 0.26 e ( 00 y 0.0 (1.44) -0.08 e r g 0.0 (1.44) -0.08 n -0.28 e (0.59) e -0.54 r e -0.5 -0.67 -0.69 --00..7722 e s f -0.81 (0.44) b -0.98 b Gi -1.0 -1.5 -1.61 -2.0 H( g) H * O H * H * T ol *) -2.5 C H O 7 7 C H O 7 7 TS1 C H * + 7 7 C H * + 7 7 TS2 C H * ( 7 8 T ol ( g) Supplementary Fig. 22 Potential energy profiles of m-cresol HDO on Ni(111) and Ni Sn(111) surfaces. 3 Supplementary Fig. 23 Schematic illustration of m-cresol HDO on Ni(111) surface with optimized structures. Supplementary Fig. 24 Schematic illustration of m-cresol HDO on Ni Sn(111) 3 surface with optimized structures. As shown in Fig. 5 and Supplementary Fig. 21-24, the activation energy of C-O cleavage is higher than that of C H * hydrogenation step on all catalysts, and it is also 7 7 higher than the activation energy of oxygen vacancy regeneration step on Ti O -Ni(111) 3 5 and Ti O -Ni Sn(111). Thus, the DFT study of full catalysis cycle confirms that C-O 3 5 3 cleavage of m-cresol is the rate determine step. For the part regarding oxygen vacancy creation, we sincerely apologize that the description “Comparable energy barriers of 0.80 eV and 0.84 eV were obtained on pure Ni and NiSn alloy surface” is mistaken. The values in this sentence represent the thermodynamic oxygen vacancy formation energy, not the energy barriers. And the recalculated value on Ni is slightly changed as 0.88 eV. The optimized structure (Supplementary Fig. 20 in SI) shows that the Ti O cluster has a higher affinity for 3 6 nickel, thus preventing direct coordination between O and Sn. Thus, the similarity in the oxygen vacancy formation energies of Ti O on Ni(111) and Ni Sn(111) surfaces 3 6 3 could be ascribed to their similar local oxygen coordination environments. For the part regarding the oxygen vacancy regeneration, we have calculated the activation barrier of this step (i.e., the adsorbed OH* fragment hydrogenation to H O). 2 The results in Fig. 5c demonstrate that the activation barrier for oxygen vacancy regeneration on Ni Sn(111) surface (0.55 eV) is lower than that on Ni(111) surface 3 (0.86 eV). This advantage could be related to the weakly adsorbed H* species on NiSn alloy that can easily attack OH* fragment on TiO cluster, which is consistent with the x DFT results of Zhao et al. (J. Catal. 2025, 450, 116333). Action: Following the reviewer’s suggestion, the Fig. 4 in the original manuscript has been replaced by the above Fig. 5, and the Supplementary Fig. 21-24 have been added in SI. In the manuscript, the sentence “m-Cresol adsorption and deoxygenation on Ti O /Ni(111) and Ti O /Ni Sn(111) surfaces were then estimated, with that estimated 3 5 3 5 3 on parent Ni(111) and Ni Sn(111) surfaces as a comparison, respectively. The 3 configurations of the stable adsorption at the initial states (IS) or final states (FS), as well as the transition states (TS) are shown in Fig. 5 and Supplementary Fig. 21.” has been revised to “The full catalysis cycle, including m-cresol adsorption, C-O cleavage, m-methylphenyl fragment (C H *) hydrogenation and oxygen vacancy regeneration 7 7 steps are investigated (Fig. 5 and Supplementary Fig. 21-24). The energy barrier comparison indicates that C-O cleavage of m-cresol is the rate determine step on all catalysts.” The discussion “This configuration with its weak adsorption energy explains the excellent anti-coking ability of NiSn alloy.” has been added after the phrase of “similar as that of the furfural adsorption on NiSn alloy surface21,28.” The sentence “Comparable energy barriers of 0.80 eV and 0.84 eV were obtained” has been revised to “Comparable thermodynamic oxygen vacancy formation energy of 0.88 eV and 0.84 eV were obtained”. Comment 2-5: Minor comments / typos: Line 138: “In contract” should be “In contrast” Line 192: “chemistry” should be “chemical” Line 205: the word “spectroscopy” should appear after “transform”, and the acronym should say “DRIFTS”. Line 448: “strength” should be “strong” Response: We appreciate the reviewer for the very kind comments and we apologize for these typo errors. Action: Following the reviewer’s reminder, “In contract” has been revised to “In contrast”; “chemistry nature” in the manuscript has been revised to “chemical nature”; “diffuse reflectance infrared fourier transform (DRIFT)” has been revised to “diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS)”, and all DRIFT in the manuscript and SI have been revised to DRIFTS; The original sentence “However, through the adsorption is not as strength as that on Ni(111) surface, the O atom in m- cresol becomes closer to the Ni Sn(111) surface” has been revised as “Despite weaker 3 adsorption of m-cresol on Ni Sn(111) compared to Ni(111), its O atom is closer to the 3 Ni Sn(111) surface”. 3 …………………………end of response to Reviewer 2………………………… Reviewer 3 Comment: This work reports on the study of TiO -modified Ni(Sn) catalysts for the x hydrodeoxygenation of m-cresol through reactivity measurements, characterization, and theoretical calculations. The work follows a consistent narrative which introduces logically increasing complexity, first through the formation of NiSn alloy nanoparticles to improve HDO reactivity and stability over Ni nanoparticles, followed by the decoration of NiSn alloy nanoparticles with TiO to facilitate reactivity. The authors x conclude that TiO and NiSn phases interact synergistically to enable enhanced HDO x by reduced C-O activation barriers and inhibited deactivation mechanisms. However, there are some questions that remain after reading the manuscript as is that should be addressed prior to consideration for publication. Those questions are: Response: We appreciate the reviewer for the positive assessment of our work and the constructive suggestions. The point-by-point responses to these suggestions are presented below. Comment 3-1: Through the manuscript, the authors are inconsistent in their assignment of deactivation behaviors. At times, they cite work which relates the formation of oxide overlayers (SMSI) to the deactivation of Ni sites by physical coverage and prevention of adsorption. Other times, they discuss the formation of coke at acidic TiO sites. In x the end, there does not seem to be a conclusion reached on which is relevant, or whether both contribute in this experimental system and sometimes the authors could be more quantitative. Response: We thank the reviewer for the comment and insightful suggestion. To more clearly describe the deactivation behavior, we have revised the manuscript from three aspects. Firstly, the introduction is revised to highlight the challenge of designing coking-resistant catalysts for phenolic HDO reactions under ambient pressure. Secondly, the coking behavior is proposed based on the HDO stability test and NH - 3 TPD characterization of Ni/SiO , Ni/TiO , NiSn/SiO and NiSn/TiO , pointing out that 2 2 2 2 metal induced coking and acid induced coking exist in this system (Fig. 2d). a 20 b Conversion OH % ) OH ( 15 d CH4 + el Yi DMB Ben 10 / n Ph CH 4 o Tol i s r 5 e v n o C 0 N i/S iO N i/TiO N iS n/S iO 2 2 N iS n/TiO 2 2 c 100 d 80 NiSn/SiO ) 2 % NiSn/TiO ( 2 60 n Ni/SiO o 2 si e r 40 v n Ni/TiO C o 20 2 0 0 50 100 150 200 250 300 350 TOS (min) Fig. 2d Schematic of coking behavior on different active sites. f g e 100 ) 15 Conversion % At last, to qu DaMntBitatively analysis the contribution of metal and acid induced coking and / Yi el d s ( i o n 1 5 0 e r c e o lu a n c c d t i i u d o a c n t t e e d o t f h ( F e i B P C T s i o e h g a l n n 4p . t r 3 i o - a p c ) o a . n k F o i i n r l s g t t l o a y d , i v d th a e e n n t c a i a f g y t e a n v e r si o n ( % ) l t y o h s f e 4 6 8 t 0 0 0 i u c n o n v v d e e e rs r r a g e g o T e e i s O o m f x 0 - - . m N 5 c 0 r T i e e S . i t 5 - s a n N o T l i l i S - a n N H n n t i / e D d / S S r O f i a O a O c c 2 f i e o d , r s a 5 i n t m e i s n i n - b s y ( i a t u s c o i p n k r i e o t i b a i e s l e r catalyst state) or 125 min (as coke d C oepo 2 s 0 ited catalyst state), then the 2 system is switched C v n o to isopropanol reaction condition. All the conversion of reactants were kept below 10% C 0 0 b ac y N e i/ t aS o d iO n j 2e u0. , s5 t w T i i n - h N g i i 1 l /Se TW i i O - t N h /F i e /S . N a iO iBS c 2 n i e d /S c 0 i a s . O 5 i u 2 T t s e i- e N c 1 i a S tTh tn i a -e / N Sl y i i S O n /S iO 0 50 100 T 1 O 5 S 0 2 (m 00 in 2 ) 50 300 350 2 2 2 100 80 60 40 20 0 0 50 100 150 200 250 300 350 f 15 Conversion DMB ) Ben % Ph ( d CH el 10 4 Tol Yi / n o si r e 5 v n o C 0 N i/S iO 2 0.5T i-N i/S iO 1T i-N i/S iO 2 N iS n/S iO 2 0.5T i-N iS n/ 1 S T iO i-N iS n/S iO 2 2 2 Fig. 3 In-situ probe reaction of isopropanol to identify the coverage of active sites 80 60 40 20 0 0 50 100 150 200 250 300 350 by coke. a Program of in-situ probe reaction of isopropanol on catalysts after m-cresol HDO. b Schematic of probing metal and acid sites via isopropanol reaction. c Percent decrease of m-cresol conversion, acetone yield and propene yield on catalysts. The conversions of m-cresol and isopropanol are all controlled below 10% by adjusting W/F. The error bars show the standard deviation of conversion or yield based on three repeated experiments. As shown in Fig. 3c, acetone is the main product on Ni/SiO , indicating that metallic 2 Ni active sites dominate the catalyst surface. During the 2 h HDO test, m-cresol conversion decreased by 51%, closely matching the 52% decrease in acetone yield. These comparable results demonstrate that the isopropanol probe reaction can effectively reflect coke coverage on active sites. On 0.5Ti-Ni/SiO , propene formation 2 is observed due to the surface acidity provided by TiO . The 66% decrease in m-cresol x conversion is more pronounced than that of Ni/SiO . Interestingly, while the acetone 2 yield deceases by 53%, similar to Ni/SiO , the propene yield decreases only by 27% on 2 0.5Ti-Ni/SiO . This observation indicates that coke predominantly covers 2 metallic Ni sites, leading to deactivation in m-cresol HDO, while TiO sites experience x less coverage. On NiSn/SiO , propene yield is negligible compared to acetone yield, demonstrating 2 that the Sn promoter does not introduce acid sites to the catalyst. The acetone yield remains constant after 2 h HDO reaction of m-cresol, consistent with the anti-coking property of NiSn alloy. After the inverse introduction of TiO , propene is formed but at a lower x yield compared to acetone. The distinct product distributions between 0.5Ti-NiSn/SiO and 0.5Ti-Ni/SiO during isopropanol reaction may be attributed to different TiO 2 2 x structures, as evidenced by Raman results. Compared to 0.5Ti-Ni/SiO , the 2 h m- 2 cresol HDO process has negligible effect on 0.5Ti-NiSn/SiO , suggesting that NiSn 2 alloy not only possesses intrinsic anti-coking property but also suppresses coke deposition on adjacent TiO sites. Consequently, the inverse TiO -NiSn interface x x enables both high activity and remarkable stability in m-cresol HDO. Action: Following the reviewer’s suggestion, the introduction has been revised to highlight the challenge of designing coking-resistant catalysts for phenolic HDO reactions under ambient pressure (not attached here for simplification). The above Fig. 2d has been added in the revised manuscript, with the following description: “Therefore, the coking behavior of catalysts in m-cresol HDO can be illustrated. As shown in Fig. 2d, coke formation occurs at two types of active sites: metallic Ni sites and TiO acid sites. Metal induced coking can be suppressed through x the formation of NiSn alloy, while acid induced coking can be mitigated by replacing the acidic TiO support with inert SiO .” 2 2 The subheading of second section in the Results has been revised to “Elucidating the anti-coking advantage of inverse TiO -NiSn interface”. The above Fig. 3 has been x added in the revised manuscript, with the following description: “To further elucidate the anti-coking advantage of inverse TiO -NiSn interface, the coverage of active sites x by coke after m-cresol HDO is investigated by an in-situ probe reaction of isopropanol (Fig. 3a). Generally, metal sites catalyze the dehydrogenation of isopropanol to acetone, while acid/oxophilic sites catalyze the dehydration of isopropanol to propene30-32 (Fig. 3b). Therefore, the coke coverage on the metal and TiO sites can be estimated from the x percentage decrease in acetone and propene yields, respectively, after m-cresol HDO. Here, the HDO reaction was conducted for 5 min (as initial catalyst state) and 125 min (as coke deposited catalyst state). As shown in Fig. 3c, acetone is the main product on Ni/SiO , indicating that metallic 2 Ni active sites dominate the catalyst surface. During the 2 h HDO test, m-cresol conversion decreased by 51%, closely matching the 52% decrease in acetone yield. These comparable results demonstrate that the isopropanol probe reaction can effectively reflect coke coverage on active sites. On 0.5Ti-Ni/SiO , propene formation 2 is observed due to the surface acidity provided by TiO . The 66% decrease in m-cresol x conversion is more pronounced than that of Ni/SiO , consistent with the more severe 2 deactivation observed at higher conversion levels in Fig. 2c. Interestingly, while the acetone yield deceases by 53%, similar to Ni/SiO , the propene yield decreases only by 2 27% on 0.5Ti-Ni/SiO . This observation indicates that coke predominantly covers 2 metallic Ni sites, leading to deactivation in m-cresol HDO, while TiO sites experience x less coverage. On NiSn/SiO , propene yield is negligible compared to acetone yield, demonstrating 2 that the Sn promoter does not introduce acid sites. The acetone yield remains constant after 2 h HDO reaction of m-cresol, confirming the inherent anti-coking property of NiSn alloy. After the inverse introduction of TiO , propene is formed but at a lower x yield compared to acetone. The distinct product distributions between 0.5Ti-NiSn/SiO 2 and 0.5Ti-Ni/SiO during isopropanol reaction may be attributed to different TiO 2 x structures, as evidenced by Raman results (Supplementary Fig. 14). Compared to 0.5Ti- Ni/SiO , the 2 h m-cresol HDO process has negligible effect on 0.5Ti-NiSn/SiO , 2 2 suggesting that NiSn alloy not only possesses intrinsic anti-coking property but also suppresses coke deposition on adjacent TiO sites. Consequently, the inverse TiO -NiSn x x interface enables both high activity and remarkable stability in m-cresol HDO.” The in-situ probe reaction experiment has been added in the activity test section: “The in-situ probe reaction of isopropanol is conducted using the same reactor. Firstly, the reduced catalyst was subjected to m-cresol HDO reaction at 350 °C for 5 or 125 min, with these times representing the fresh catalyst state and coke deposited catalyst state, respectively. Then the system was purged by N (20 ml/min) and cooled to 250 °C. 2 After that, isopropanol was injected through the pump and the yields of acetone and propene were analyzed online at 15 min time on stream (TOS). The conversions of m- cresol and isopropanol are all controlled below 10% by adjusting W/F.” Comment 3-2: For example, in the comparison of Ni/TiO and Ni/SiO , the TiO 2 2 2 supported material deactivates from 95 to 5% conversion whereas Ni/SiO deactivates 2 from 95% to 50% conversion. Is this consistent with the 2x amount of C deposition for Ni/TiO compared to Ni/SiO ? 2 2 Response: We thank the reviewer for the comment. In the manuscript, we have described that “The Ni/TiO deactivates at a significantly higher rate as compared to 2 Ni/SiO . Correspondingly, the total coke deposition (based on the integrated area of 2 CO ) on Ni/TiO is two times higher than that on Ni/SiO .” We sincerely apologize for 2 2 2 the omission of the quantitative analysis of the O -TPO profile. 2 Action: Following the reviewer’s comment, The O -TPO profile in Supplementary Fig. 2 11 has been presented with baseline for integration, and the corresponding quantitative results have been listed in Supplementary Table 2. 529 0.005 328 Ni/TiO 2 ) u. a. 314 ( 4 NiSn/TiO 4 2 = z m/ 310 Ni/SiO 2 NiSn/SiO 278 2 100 200 300 400 500 600 700 T (C) Supplementary Fig. 11 O -TPO profile of spent catalysts. 2 Supplementary Table 2 Coke deposition on different catalysts obtained from quantitative analysis of O -TPO profile in Supplementary Fig. 11. 2 Coke formation Catalyst Integral Area (a.u.) g /g (%) carbon catalyst Ni/SiO 1.77 1.21 2 NiSn/SiO 0.19 0.13 2 Ni/TiO 3.62 2.48 2 NiSn/TiO 1.68 1.15 2 The original sentence “Correspondingly, the total coke deposition (based on the integrated area of CO ) on Ni/TiO is two times higher than that on Ni/SiO .” has been 2 2 2 revised to a more clearly description: “Correspondingly, the total coke deposition on Ni/TiO is two times higher than that on Ni/SiO (Supplementary Table 2).” 2 2 Comment 3-3: Staying on the note about deactivation – the authors focus on the acidity of TiO as a mediator for coke formation and thus deactivation. Upon formation of 2 interaction between Sn and TiO , the authors observe increased stability – this would x lead one to consider that Sn has reduced the acidity of TiO . How would this happen? x What chemical effect would lead to this? Response: We thank the reviewer for the comment. The catalysts related to TiO and x Sn species mentioned in this comment can be classified to two groups: (1) Ni/TiO and 2 NiSn/TiO ; (2) 0.5Ti-Ni/SiO and 0.5Ti-NiSn/SiO . Meanwhile, we have performed 2 2 2 NH -TPD characterization of catalysts and added as Supplementary Fig. 12 and 3 Supplementary Table 3, showing below. Weak Medium Strong Weak Medium Strong 100 172 300 100 175 277 NiSn/TiO Ni/TiO 2 2 94 96 u. ) 1 1 a. ( 6 = 1 93 0.5Ti-Ni/SiO 2 0.5Ti-NiSn/SiO 2 z 91 m/ Ni/SiO NiSn/SiO 2 2 100 200 300 400 500 100 200 300 400 500 T (C) T (C) Supplementary Fig. 12 NH -TPD curves of reduced catalysts. 3 Supplementary Table 3 Quantitative results of acidity from Supplementary Fig. 12. Acid density (μmol/g) Catalyst Weak Medium Strong Ni/SiO 11.78 0 0 2 NiSn/SiO 8.35 0 0 2 0.5Ti-Ni/SiO 12.49 6.77 0 2 0.5Ti-NiSn/SiO 9.67 8.53 0 2 Ni/TiO 4.48 9.76 13.63 2 NiSn/TiO 3.69 7.47 7.91 2 In the first group: compared to Ni/TiO , NiSn/TiO exhibits a higher HDO stability, 2 2 while the acidity is lower, which is consistent with the reviewer’s inference; However, in the second group: compared to 0.5Ti-Ni/SiO , 0.5Ti-NiSn/SiO exhibit a higher 2 2 HDO stability, while the acidity is similar to the former catalyst. Additionally, the “formation of interaction between Sn and TiO ” may exist on the catalysts, but TEM x results (Supplementary Fig. 4 and Fig. 4b) demonstrate that Sn is interacted with Ni and form NiSn alloy, which is also supported by the Sn0 state detected by XPS (Supplementary Fig. 19d). In the revised manuscript, we have demonstrated that both metallic Ni and acidic TiO contribute to the coking deactivation 2 (see the response of Comment 3-1). Based on the above discussion, we believe that the main role of Sn is to interact with Ni to form NiSn alloy, which suppresses metallic Ni induced coking, as further confirmed by the study of the third group: Ni/SiO and NiSn/SiO . 2 2 Comment 3-4: The estimation of TiO coverage by CO DRIFTS is potentially not x reliable, which the authors attempt to convey by calling the results “semi-quantitative”. Can the authors provide further detail about their DRIFTS quantification so that an assessment of the validity of their approach can be made? Is the quantification different if absorbance units are used instead of Kubelka-Munk? Is it possible to conduct a more quantitative analysis such as CO pulsed chemisorption? Response: We appreciate the reviewer for this important comment and suggestion. We agree with the reviewer and recognize that the existence of scattering effect makes DRIFTS more challenging in quantitative analysis than the transmission infrared spectroscopy, especially when comparing band intensities between different samples. Thus, following the reviewer’s suggestion, the TiO coverage on Ni or NiSn sites is x measured using CO pulsed chemisorption. Supplementary Table 6 TiO coverage on Ni or NiSn sites of inverse catalyst measured by x CO pulsed chemisorption. Catalyst n /n a TiO coverage (%)b CO Ni x Ni/SiO 0.0219 2 0.5Ti-Ni/SiO 0.0101 53.9 2 NiSn/SiO 0.0118 2 0.5Ti-NiSn/SiO 0.0098 16.9 2 a n is the adsorbed CO molar amount obtained from CO pulsed chemisorption, while n is the Ni CO Ni molar amount calculated from ICP-OES results in Supplementary Table 1. b TiO coverage% = 1- (n /n ) /( n /n ) x CO Ni parent catalyst CO Ni TiOx loaded catalyst As shown in Supplementary Table 6, the TiO coverage of Ni sites on 0.5Ti-Ni/SiO is x 2 53.9%, while the value is lower for 0.5Ti-NiSn/SiO (16.9%). This trend is consistent 2 with the observed trend from CO-DRIFTS studies. Action: The above Supplementary Table 6 has been added in SI; The sentence “The semi-quantified surface coverage of TiO on the Ni surface, estimated at approximately x 23%, was derived from the reduction in CO adsorption area compared to the total CO adsorbed area.” has been deleted, while “The TiO coverage on Ni site was determined x as 53.9% by CO pulsed chemisorption (Supplementary Table 6).” has been added after the sentence “coordinating with these sites and altering their electronic properties.” The sentence “giving a semi-quantified TiO coverage of ~9% with respect to Ni atoms.” x has been revised to “resulting in the 16.9% TiO coverage on Ni atoms (Supplementary x Table 6).” The CO pulsed chemisorption process has been added to the catalyst characterization section: “CO pulsed chemisorption was performed on the same instrument. The catalyst was firstly reduced in H at 400 °C for 1 h, followed by Ar 2 purging for 0.5 h. After cooling to room temperature, the CO pulsed chemisorption was conducted with 0.5 mL 1%CO/Ar per loop until the adsorption was saturated. The outlet gas was analyzed using the Pfeiffer Omistar quadrupole online MS, observing the CO signal with m/z = 28.” Comment 3-5: Do the authors have insight into the experimental error for their temperature-dependent reaction measurements made to assess apparent activation barriers? What is the statistical significance of the difference in barriers between these two materials? Response: We thank the reviewer for this important reminder. Based on three repeated experiments, the points are redrawn using the average values and the error bars are added to show the standard deviation of Ln(r ). As shown in Supplementary Fig. 8, Tol the data demonstrate statistical significance with small measurement errors. Despite a slight shift in the E values compared to the original ones, the trend remains the same: act E is lower on NiSn/TiO . act 2 2.0 NiSn/TiO 2 1.5 E = 65.8 4.5 kJ/mol act ) R2= 0.98 h 1.0 / at gc ol/ 0.5 m m ol 0.0 T r NiSn/SiO n ( 2 L -0.5 E = 86.2 8.3 kJ/mol act R2= 0.99 -1.0 1.60 1.65 1.70 1.75 1000/T (K-1) Supplementary Fig. 8 Arrhenius plots of m-cresol deoxygenation to toluene on NiSn/SiO and NiSn/TiO catalysts. Reaction conditions: P = 1 atm, H /m-cresol = 60, 2 2 2 TOS = 20 min, conversion was kept under 10% by adjusting the W/F. The error bars show the standard deviation of Ln(r ) based on three repeated experiments. Tol Action: The original figure has been replaced by the above Supplementary Fig. 8 in SI, and the E values in the corresponding description are updated. act Comment 3-6: I have questions about the H/D exchange experiments and their analysis. The authors approach the data with the assumption that H (D ) activation is rate- 2 2 limiting in the case of all catalysts. Could it not also be that HD desorption is rate- limiting, and that the data may point towards stronger H(D) adsorption? Response: We thank the reviewer for the comment. In the H -D TPSR study, we also 2 2 provide the H and D reactant curves in addition to the HD product curve. If HD 2 2 desorption is the rate-limiting step, HD formation would lag behind the consumption of H and D . However, the results show that the increase of HD product occurs 2 2 simultaneously with the decrease of H and D reactants. Thus, it can reflect the 2 2 variation in H activation ability across different catalysts. 2 Action: For clear explanation, the sentence “the increase of HD product occurs simultaneously with the decrease of H and D reactants, thus reflecting the variation 2 2 in H activation ability across different catalysts” has been added after “As shown in 2 Supplementary Fig. 9” in Supplementary Discussion 1. Comment 3-7: Has TPO been performed on the as-synthesized 0.5Ti-Ni(Sn)/SiO 2 catalysts? The SI notes that hydrolysis of the titanium precursor was allowed to occur in atmosphere and then calcination was performed at 300˚C for 1 hr. Do the authors have evidence that the TiO -phase formed, which remains amorphous, does not still contain carbonaceous species? x Response: We thank the reviewer for the insightful comment. Following the reviewer’s suggestion, we conducted TPO test on the as-synthesized 0.5Ti-Ni(Sn)/SiO catalysts, 2 and the results are shown in Supplementary Fig. 13 and Supplementary Table 4 below. 347 0.005 542 u.) 0.5Ti-Ni/SiO 2 a. 307 4 ( = 4 z 0.5Ti-NiSn/SiO m/ 2 0.5Ti-Ni/SiO-Fresh 2 0.5Ti-NiSn/SiO-Fresh 2 100 200 300 400 500 600 700 800 T (C) Supplementary Fig. 13 O -TPO profile of the fresh and spent inverse catalysts. 2 Supplementary Table 4 Coke deposition on different catalysts obtained from quantitative analysis of O -TPO profile in Supplementary Fig. 13. 2 Coke formation Catalyst Integral Area (a.u.) g /g (%) carbon catalyst 0.5Ti-Ni/SiO 3.47 2.38 2 0.5Ti-NiSn/SiO 1.08 0.74 2 0.5Ti-Ni/SiO -Fresh 3.88×10-6 1.82×10-6a 2 0.5Ti-NiSn/SiO -Fresh 0.1×10-6 0.63×10-6a 2 a Residual amount of carbonaceous species on the fresh inverse catalysts. The results demonstrate that the residual amount of carbonaceous species on the fresh inverse catalyst is negligible. Action: Based on the reviewer’s suggestion, the original Fig. S10 has been replaced by the above Supplementary Fig. 13, and Supplementary Table 4 has also been added in SI. The sentence “O -TPO analysis of the fresh catalysts indicates that the carbonaceous 2 species from tetrabutyl titanate are almost removed (Supplementary Fig. 13 and Supplementary Table 4)” has been added after “where x refers to the nominal molar ratio of Ti to Ni”. Comment 3-8: The paper assumes that Sn is reduced in-situ (in the discussion and DFT calculations). But it seems likely that Sn may partially oxidize when interaction with TiO overlayers. Could this be addressed? x Response: We thank the reviewer for the comment. Sn 3d XPS results of NiSn/SiO 2 and 0.5Ti-NiSn/SiO are shown in Supplementary Fig. 19d, confirming a consistent 2 electronic state of Sn element on both catalysts. The observed binding energy demonstrates the presence of metallic Sn0, with no detectable oxidized Sn species. In addition, the Ti3+ species is also detected by XPS (Supplementary Fig. 19c), indicating the existence of oxygen vacancies from partially reduced TiO . As electron donors, x these oxygen vacancies provide electrons to Ni and Sn sites, thus stabilizing the Ni0 and Sn0 species structurally. The electron-donating characteristic of partially reduced TiO x has been widely reported (J. Am. Chem. Soc. 2024, 146, 2290−2307; Nat. Comm. 2022, 13, 6720; J. Am. Chem. Soc. 2018, 140, 11241−11251) and also observed by Ni XPS and CO-DRIFT in our work. Thus, TiO could ensure the state of Sn0, but is not likely x to oxidize Sn species here. Comment 3-9: Further, it seems that Sn incorporation into Ni may change the structure or nature of the TiO overlayer or alloy surface structure) (e.g. TiO causes Ni domain x x aggregation and Sn aggregation). Can the authors comment on this? Response: We thank the reviewer for this insightful comment. We will discuss it from two issues. The first issue is whether the TiO structure exhibits difference on Ni versus x NiSn surface. The following evidence indicates that the difference is existed. Raman characterization (Supplementary Fig. 14) of 0.5Ti-Ni/SiO observed that the E mode 2 g had blue-shifted to 149 cm-1 and broadened in the full width at half maximum (from ~18 to ~24 cm-1) compared to TiO supported catalysts, which is related to phonon 2 confinement and could be ascribed to the decrease of the TiO thickness with respect to x the TiO nanoparticles (Phys. Chem. Chem. Phys. 2016, 18, 32178-32184). However, 2 any Raman signal of TiO species was undetectable with 0.5Ti-NiSn/SiO . In case that x 2 limited TiO content on this catalyst caused the weak response to Raman laser, the 1Ti- x NiSn/SiO with the Ti content being doubled were tested, but still showed no signal. It 2 demonstrates an amorphous structure of TiO on the NiSn alloy particles (Optical x Materials 2011, 33, 1907-1910), possibly deriving from the unique interaction between TiO and NiSn alloy phases. Theoretical calculations (Supplementary Fig. 20) further x confirm distinct structural differences of TiOₓ species on Ni versus NiSn surface. This discrepancy originates from the dual role of Sn species: inducing repulsion towards oxygen atoms while creating spatial separation of surface Ni atoms, consequently leading to weaker bonding between TiOₓ species and the NiSn surface compared to the pure Ni surface. The second issue is whether the introduction of TiO species would induce aggregation x of Ni or Sn on the NiSn catalyst. The elemental compositions of NiSn/SiO and 0.5Ti- 2 NiSn/SiO detected by XPS survey scan are shown in Supplementary Table 7 below: 2 Supplementary Table 7 Elemental compositions of catalysts detected by XPS survey scan. Atom concentration (%) Catalyst Ni/Sn Ni Sn Ti O Si Ni/SiO 0.30 69.81 29.89 2 0.5Ti-Ni/SiO 0.34 0.67 69.74 29.24 2 NiSn/SiO 0.31 0.33 69.65 29.71 0.94 2 0.5Ti-NiSn/SiO 0.39 0.40 0.52 68.94 29.75 0.98 2 The results present a similar Ni/Sn atomic ratio between NiSn/SiO and 0.5Ti- 2 NiSn/SiO , indicating that the introduction of TiO species would not induce 2 x aggregation of Ni or Sn on the NiSn catalyst. Action: Based on the reviewer’s comment, we have added the above Supplementary Table 7 in SI, and the description “In addition, XPS survey scan shows that the surface Ni/Sn ratio is not influenced by the inverse introduction of TiO species (Supplementary x Table 7).” has been added at the last paragraph of “Geometric and electronic structure of inverse TiO -NiSn interface” section. x …………………………end of response to Reviewer 3………………………… Reviewer 4 Comment: I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts. Response: We appreciate the reviewer for the comments and the constructive suggestions of our work. Our point-by-point responses to comments are presented in the above contexts. …………………………end of response to Reviewer 4………………………… Point-by-point response to the reviewer comments (Comments in black, Responses in blue and dark red) Reviewer 1 Comment: The authors have done an outstanding job addressing the comments I made in my review. I am now satisfied and recommend that the manuscript be accepted for publication. Response: We appreciate the time and effort the reviewer has invested in reviewing our manuscript. …………………………end of response to Reviewer 1………………………… Reviewer 2 Comment: The authors have been very thorough in addressing the referee comments, and I think the restructuring of the manuscript has significantly improved it. I recommend publication of this version. Response: We appreciate the time and effort the reviewer has invested in reviewing our manuscript. …………………………end of response to Reviewer 2………………………… Reviewer 3 Comment: In response to the initial round of comments by reviewers, the authors have made substantial revisions to the original manuscript which have greatly improved the narrative quality and experimental rigor of the work. Overall, the utility of a NiSn alloy surface in mitigating metal-based coking while continuing to provide the desirable HDO characteristics of Ni is clear, well-supported, and well-communicated. However, the structure-function relationships underlying the inverse TiO catalyst formulations x remain underdeveloped. The authors of this manuscript might consider the following comments in the continued refinement of this manuscript: Response: We appreciate the time and effort the reviewer has invested in reviewing our manuscript. The point-by-point responses to the continued comments and suggestions are presented below. Comment 3-1: The isopropanol probe reactions are an elegant addition to the manuscript which nicely demonstrates the structure-specific effects of coking during HDO reactivity. However, these results do raise more questions regarding the chemical nature of the TiO overlayer present in Ni and NiSn catalysts. For example, in the x isopropanol probe reaction, Ni and NiSn catalysts without TiO perform roughly x identically, suggesting that the intrinsic isopropanol reactivity of both surfaces are comparable. However, upon TiO introduction, TiO -Ni and TiO -NiSn catalysts perform vastly x x x differently in the isopropanol probe reaction. The authors do not address this directly, and characterization of the TiO overlayers and the associated chemical properties is x limited (NH -TPD, Raman, CO chemisorption). Can the authors consider and comment 3 on a likely mechanism by which TiOx decorated Ni and NiSn catalysts could perform so differently in the isopropanol probe reaction? Might this be related to the enhanced m- cresol reactivity observed only for TiO -NiSn, while TiO -Ni experiences a loss of x x activity (though an increase in toluene yield). Are the interfacial sites sufficiently comparable in TiO -Ni and TiO -NiSn, or are their differences sufficient to be considered x x unique active sites? Response: We thank the reviewer for the insightful suggestion and will respond to this point in three parts. 1. Limitations of TiO characterization and different performance between TiO - x x NiSn/SiO and TiO -Ni/SiO in isopropanol probe reaction. We must acknowledge that 2 x 2 the characterization of TiO species is challenging due to the low content and high x dispersion. We attempted to characterize the TiO structure using XAS, but no relevant x signals were detected. Despite this, we designed control experiments to interpret the differences in the isopropanol reaction between the two catalysts. Specifically, a Ti/SiO sample was prepared using the same slow hydrolysis method, 2 while a Ti/SiO (f) sample was prepared by the same process but with ethanol replaced 2 by H O to achieve fast hydrolysis of tetrabutyl titanate prior to impregnation. The TiO 2 x loading is the same as that of 0.5Ti-Ni/SiO . Raman spectra in Supplementary Fig. 15a 2 reveal that Ti/SiO exhibits an amorphous TiO state with no detectable bands, while 2 x Ti/SiO (f) displays Raman bands corresponding to the crystalline TiO nanoparticles. 2 2 The isopropanol reaction test shows that both Ti/SiO and Ti/SiO (f) exhibit 2 2 dehydration activity, with propene as the dominant product (Supplementary Fig. 15b). The propene yield of Ti/SiO (f) is about 2.2 times higher than that of Ti/SiO , a 2 2 difference comparable to that between 0.5Ti-Ni/SiO and 0.5Ti-NiSn/SiO . These 2 2 findings demonstrate that the different performance in isopropanol reaction is related to the TiO structure: the highly dispersed crystalline TiO state provides a higher x x dehydration activity than the amorphous TiO state. x a b 10 Propene Acetone 146 639 8 u.) 400 517 Ti/SiO(f) a. 307 4 ( = 4 z 0.5Ti-Ni/SiO 2 0.5Ti-NiSn/SiO 2 0.5Ti-Ni/SiO-Fresh 2 0.5Ti-NiSn/SiO-Fresh 2 100 200 300 400 500 600 700 800 T (C) Supplementary Fig. 13 O -TPO profile of the fresh and spent inverse catalysts. 2 Supplementary Table 4 Coke deposition on different catalysts obtained from quantitative analysis of O -TPO profile in Supplementary Fig. 13. 2 Coke formation Catalyst Integral Area (a.u.) g /g (%) carbon catalyst 0.5Ti-Ni/SiO 3.47 2.38 2 0.5Ti-NiSn/SiO 1.08 0.74 2 0.5Ti-Ni/SiO -Fresh 3.88×10-6 1.82×10-6a 2 0.5Ti-NiSn/SiO -Fresh 0.1×10-6 0.63×10-6a 2 a Residual amount of carbonaceous species on the fresh inverse catalysts. The results demonstrate that the residual amount of carbonaceous species on the fresh inverse catalyst is negligible. Action: Based on the reviewer’s suggestion, the original Fig. S10 has been replaced by the above Supplementary Fig. 13, and Supplementary Table 4 has also been added in SI. The sentence “O -TPO analysis of the fresh catalysts indicates that the carbonaceous 2 species from tetrabutyl titanate are almost removed (Supplementary Fig. 13 and Supplementary Table 4)” has been added after “where x refers to the nominal molar ratio of Ti to Ni”. Comment 3-8: The paper assumes that Sn is reduced in-situ (in the discussion and DFT calculations). But it seems likely that Sn may partially oxidize when interaction with TiO overlayers. Could this be addressed? x Response: We thank the reviewer for the comment. Sn 3d XPS results of NiSn/SiO 2 and 0.5Ti-NiSn/SiO are shown in Supplementary Fig. 19d, confirming a consistent 2 electronic state of Sn element on both catalysts. The observed binding energy demonstrates the presence of metallic Sn0, with no detectable oxidized Sn species. In addition, the Ti3+ species is also detected by XPS (Supplementary Fig. 19c), indicating the existence of oxygen vacancies from partially reduced TiO . As electron donors, x these oxygen vacancies provide electrons to Ni and Sn sites, thus stabilizing the Ni0 and Sn0 species structurally. The electron-donating characteristic of partially reduced TiO x has been widely reported (J. Am. Chem. Soc. 2024, 146, 2290−2307; Nat. Comm. 2022, 13, 6720; J. Am. Chem. Soc. 2018, 140, 11241−11251) and also observed by Ni XPS and CO-DRIFT in our work. Thus, TiO could ensure the state of Sn0, but is not likely x to oxidize Sn species here. Comment 3-9: Further, it seems that Sn incorporation into Ni may change the structure or nature of the TiO overlayer or alloy surface structure) (e.g. TiO causes Ni domain x x aggregation and Sn aggregation). Can the authors comment on this? Response: We thank the reviewer for this insightful comment. We will discuss it from two issues. The first issue is whether the TiO structure exhibits difference on Ni versus x NiSn surface. The following evidence indicates that the difference is existed. Raman characterization (Supplementary Fig. 14) of 0.5Ti-Ni/SiO observed that the E mode 2 g had blue-shifted to 149 cm-1 and broadened in the full width at half maximum (from ~18 to ~24 cm-1) compared to TiO supported catalysts, which is related to phonon 2 confinement and could be ascribed to the decrease of the TiO thickness with respect to x the TiO nanoparticles (Phys. Chem. Chem. Phys. 2016, 18, 32178-32184). However, 2 any Raman signal of TiO species was undetectable with 0.5Ti-NiSn/SiO . In case that x 2 limited TiO content on this catalyst caused the weak response to Raman laser, the 1Ti- x NiSn/SiO with the Ti content being doubled were tested, but still showed no signal. It 2 demonstrates an amorphous structure of TiO on the NiSn alloy particles (Optical x Materials 2011, 33, 1907-1910), possibly deriving from the unique interaction between TiO and NiSn alloy phases. Theoretical calculations (Supplementary Fig. 20) further x confirm distinct structural differences of TiOₓ species on Ni versus NiSn surface. This discrepancy originates from the dual role of Sn species: inducing repulsion towards oxygen atoms while creating spatial separation of surface Ni atoms, consequently leading to weaker bonding between TiOₓ species and the NiSn surface compared to the pure Ni surface. The second issue is whether the introduction of TiO species would induce aggregation x of Ni or Sn on the NiSn catalyst. The elemental compositions of NiSn/SiO and 0.5Ti- 2 NiSn/SiO detected by XPS survey scan are shown in Supplementary Table 7 below: 2 Supplementary Table 7 Elemental compositions of catalysts detected by XPS survey scan. Atom concentration (%) Catalyst Ni/Sn Ni Sn Ti O Si Ni/SiO 0.30 69.81 29.89 2 0.5Ti-Ni/SiO 0.34 0.67 69.74 29.24 2 NiSn/SiO 0.31 0.33 69.65 29.71 0.94 2 0.5Ti-NiSn/SiO 0.39 0.40 0.52 68.94 29.75 0.98 2 The results present a similar Ni/Sn atomic ratio between NiSn/SiO and 0.5Ti- 2 NiSn/SiO , indicating that the introduction of TiO species would not induce 2 x aggregation of Ni or Sn on the NiSn catalyst. Action: Based on the reviewer’s comment, we have added the above Supplementary Table 7 in SI, and the description “In addition, XPS survey scan shows that the surface Ni/Sn ratio is not influenced by the inverse introduction of TiO species (Supplementary x Table 7).” has been added at the last paragraph of “Geometric and electronic structure of inverse TiO -NiSn interface” section. x …………………………end of response to Reviewer 3………………………… Reviewer 4 Comment: I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts. Response: We appreciate the reviewer for the comments and the constructive suggestions of our work. Our point-by-point responses to comments are presented in the above contexts. …………………………end of response to Reviewer 4………………………… Detailed comments: 1. The following sentence is ungrammatical On one hand, it prevents the sintering of Ni particles (as indicated by the 151 reduced Ni particle size on TiO2). 2. This point needs more explanation – where is the integrated area of CO2 coming from and how does this correspond to the amount of coke on the surface. Correspondingly, the total coke deposition (based on the integrated area of CO2) on 159 Ni/TiO2 is two times higher than that on Ni/SiO2. 3. How often is reduction required? Prior to analysis, the catalysts were reduced at 400 °C for 1 h 4. The following sentence is ungrammatical rendering it higher activity toward target 192 deoxygenation reaction.26,37 5. The following sentence is ungrammatical It has showed identical IR characteristics between pure Ni and NiSn alloy 208 sites, while the support compositions cause major difference 6. Explain what is occurring here in terms of changes in the electronic structure. In contrast, the TiO2 213 support induced a red shift of 10 cm-1 for ν(CCring) and ν(CH3) bands and a red shift of 214 6 cm-1 for δ(OH) band, demonstrating a stronger adsorption and activation of m-cresol 215 on the Ni/NiSn-TiO2 interfacial sites compared to the pure metal/alloy surfaces 7. what is the rrror in these measurements? As shown in 225 Figure 1E, the NiSn/TiO2 catalyst exhibited a lower activation barrier of ~63 kJ/mol 226 than that of ~99 kJ/mol on NiSn/SiO2. 8. The Ti in figure 2A does not look okay (A) A scheme for inverse loading TiOx 9. The following phrase is ungrammatical To construct inverse structure (270) 10. Line 300 “semi quantified”? What is the reason not to simply quantify Ti? 11. There are a lots of quantification methods that do not add much or any value to overall narrative – should be shifted to SI (e.g. Raman, XRD, EXAFS) 12. The following phrase is ungrammatical: DFT study was conducted- should be A DFT study 13. The following phrase is ungrammatical However, through the 447 adsorption is not as strength as that on Ni(111) surface, 14. What evidence is there a Ti3O6 cluster. is the right way to model Ti? 15. What evidence is there that O vacancies are important? In the SI 1. Need more information about composition – what phase? Particle size? commercial TiO 2 2. Was this held at 580 C after ramping at this rate? calcined in a muffle furnace at 580 °C for 3 h at a heating rate of 2 °C/min 3. There is not enough information on the section below. 0.20 g Ni(NO )·6H O was dissolved in a certain amount of distilled water, and drop added 3 2 to 2.0 g support, 4. There is insufficient detail in the section below. Need to know amounts of everything. Synthesis of inverse TiO -Ni/SiO and TiO -NiSn/SiO catalysts: Tetrabutyl titanate was x 2 x 2 used as the TiO precursor. As the tetrabutyl titanate was easy to be hydrolyzed, we firstly x dissolved tetrabutyl titanate in ethanol, and then drop added to the as-prepared Ni/SiO or 2 NiSn/SiO catalysts and impregnation overnight. While exposing to the air, the H O in air would 2 2 make tetrabutyl titanate be slowly hydrolyzed and deposited as TiO . The carbon ligand was x removed by calcination in air at 300 °C for 1 h at a heating rate of 10 °C/min. The catalyst was named as xTi-M/SiO (M=Ni or NiSn), where x refers to the nominal molar ratio of Ti to Ni. 2 5. The meaning of the phrase below is unclear. The catalyst was reduced at 400 °C in H for 1 h before reaction if there are no additional 2 notes. 6. How was the reactant vaporized? and vaporized before entering the reactor. 7. What does this mean? To consider the computation accuracy and cost comprehensively, 8. Where does the, ΔZPE is the correction in zero-point energies come from. 9. What are the values for entropy? What is the justification for ignoring entropy everywhere else? 10. Figure S1. XRD patterns of different catalysts. The catalysts were pre-reduced at 400 °C for 1 h What is the green highlight for? 11. Figure S9. H -TPR profiles over different catalysts – explain arrows in caption, label peak 2 maxima In response to the initial round of comments by reviewers, the authors have made substantial revisions to the original manuscript which have greatly improved the narrative quality and experimental rigor of the work. Overall, the utility of a NiSn alloy surface in mitigating metal- based coking while continuing to provide the desirable HDO characteristics of Ni is clear, well- supported, and well-communicated. However, the structure-function relationships underlying the inverse TiO catalyst formulations remain underdeveloped. The authors of this manuscript might x consider the following comments in the continued refinement of this manuscript: 1.) The isopropanol probe reactions are an elegant addition to the manuscript which nicely demonstrates the structure-specific effects of coking during HDO reactivity. However, these results do raise more questions regarding the chemical nature of the TiO overlayer x present in Ni and NiSn catalysts. For example, in the isopropanol probe reaction, Ni and NiSn catalysts without TiO perform roughly identically, suggesting that the intrinsic x isopropanol reactivity of both surfaces are comparable. However, upon TiO introduction, TiO -Ni and TiO -NiSn catalysts perform vastly x x x differently in the isopropanol probe reaction. The authors do not address this directly, and characterization of the TiO overlayers and the associated chemical properties is limited x (NH -TPD, Raman, CO chemisorption). Can the authors consider and comment on a 3 likely mechanism by which TiOx decorated Ni and NiSn catalysts could perform so differently in the isopropanol probe reaction? Might this be related to the enhanced m- cresol reactivity observed only for TiO -NiSn, while TiO -Ni experiences a loss of x x activity (though an increase in toluene yield). Are the interfacial sites sufficiently comparable in TiO -Ni and TiO -NiSn, or are their differences sufficient to be considered x x unique active sites? 2.) The DFT assumes that a TiO trimer is the appropriate overlayer model for both Ni and x NiSn catalysts, despite Raman evidence that these materials are structurally distinct. The authors cite many works which have generally found that oxide overlayer stability and properties remain stable for Ti O species for n > 3, hence rationalizing the broad use of a n x trimer model for these systems. However, is this applicable to the TiO -NiSn catalyst x where TiO species are amorphous? Could changes in domain size/organization explain x the seemingly distinct chemical properties of TiO on Ni and TiO on NiSn? x x 3.) The CO DRIFTS data is extensive but does not communicate a strong conclusion regarding the state of the surface in the presence of TiO overlayers. For instance, the x authors state, “This band, assigned to Ni(CO) species physically adsorbed on Ni and/or SiO 4 2 support, disappeared upon Ar flushing, suggesting its formation involved subcarbonyl intermediates on defected Ni surfaces which could lead to nickel tetracarbonyl formation” – essentially correlating Ni(CO) formation with under-coordinated sites on the surfaces 4 of Ni nanoparticles. In the next segment, though, the authors also state, “…TiO decoration on Ni reduced the number of defect Ni sites…However, the x Ni(CO) band at 2056 cm-1 intensified and slightly red-shifted to 2054 cm-1, 4 suggesting that the TiO modified surface was more active in converting Ni x subcarbonyl to Ni(CO) ”. 4 If Ni(CO) forms on under-coordinated sites, but TiO reduces the number of defected 4 x (under-coordinated) sites, how can this mechanism explain the higher concentration of Ni(CO) for TiOx-decorated species? Can the authors also include relevant citations to 4 substantiate their assignment of peak locations (relevant as well for the XPS data as will be discussed below)? I am surprised that CO adsorbed on defected (under-coordinated) Ni sites would occur at 2090 cm-1, as this is typically within the range of CO adsorbed on well-coordinated metal sites. 4.) Regarding the XPS spectra once again, the authors assign the Sn 3d feature to Sn0 5/2 species. However, the Sn0 photoelectron is typically observed at 485.2 eV, Sn2+ at 486 eV, and Sn4+ at 486.6 eV (see figure below). Nearly all of these features would fall within the envelope of the broad feature shown in Fig. S19 unilaterally assigned to Sn0. Was there any attempt made to fit the Sn spectra quantitatively to determine whether other oxidation states of Sn might be present? 5.) The DFT model proposed also assumes a Ni Sn surface, while the XPS indicates that the 3 Ni:Sn ratio is closer to 1:1 (and actually shows more surface Sn than surface Ni). This would suggest that the surface is far more Sn-rich than anticipated and modelled based on the alloy model chosen. The authors may choose to acknowledge this distinction."}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors have done an outstanding job addressing the comments I made in my review. I am now satisfied and recommend that the manuscript be accepted for publication.", "reviewer_2": "The authors have been very thorough in addressing the referee comments, and I think the restructuring of the manuscript has significantly improved it. I recommend publication of this version.", "reviewer_4": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": ""}, {"round": 3, "reviewer_comments": {"reviewer_3": "The authors have very carefully addressed the referee comments. The paper can be published. This is a very nice work.", "reviewer_4": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": ""}]

Decision letter