Active site design enables industrial scale H_2O_2 electrosynthesis with metal-free catalysts

Domain: chemistry
Published: 2026-03-25
Editorial outcome: major_revision

Abstract
The electrosynthesis of hydrogen peroxide via a two-electron oxygen reduction reaction enables decentralized hydrogen peroxide (H O ) production. While metal-free carbon catalysts are
2 2
sustainable and low-cost, their performance is hindered by poorly defined active sites and
uncontrolled defect states. Here, we resolve these challenges through active site design and
catalysts screening using fluorine (F) and nitrogen (N) codoped carbon as model materials.
Statistical analysis combined with Density Functional Theoretical calculations reveals that F-
induced structural modification and defect passivation optimizeS OOH* binding, with F-doping and
adjacent F atoms predominantly lowering abs(ΔG )R.
OOH*
Experimental results confirm that semi-
ionic C–F bonds passivate defects in nitrogen-do ped carbon, enhancing catalytic activity and
durability. The resulting (N, F)-codoped carboIn achieves nearly 100% H
2
O
2
selectivity at 0.5-0.65
V vs. RHE and maintains > 95% across 0.01-0.65 V versus the reversible hydrogen electrode. In
an electrolyzer, (N, F)-codoped carbon exhibits an H O yield rate of 74.35 mol g -1 h-1 and
2 2 cat.
sustains 300 mA cm-2 for 105 hours with ~95% faradaic efficiency. Coupling the two-electron
oxygen reduction reaction with methanol oxidation further reduces cell voltage and enhances
productivity. This work provides a means to design efficient catalysts for industrial H O
2 2
electrosynthesis.

Introduction
Hydrogen peroxide (H O ) is widely employed in many crucial industries, such as
2 2
semiconductor manufacturing, wastewater treatment, and chemical synthesis.1,2 Electrosynthesis
of H O using two-electron oxygen reduction reaction (2e⁻ ORR) offers a sustainable and
2 2
decentralized alternative to the traditional anthraquinone oxidation (AO) process.2,3 The key to
efficient 2e⁻ ORR lies in precisely regulating the adsorption of the OOH* intermediate on
catalytically active sites (ASs).4 Strong OOH* binding favors the competing four-electron (4e-
ORR) pathway to H O,5 whereas weak binding limits OOH* formation and stability.6 Therefore,
2
Precise prediction and regulation of OOH* adsorption energy is essential for efficient catalyst
screening and the commercialization of H O electrosynthesis. Both metal-based and metal-free
2 2
carbon catalysts have been explored for selective 2e⁻ ORR.2,3,7,8 Metal-based catalysts, particularly
transition-metal single-atom or dual-atom sites, benefit Sfrom well-defined coordination
environments that enable relatively straightforward perfRormance prediction.9,10 On the other hand,
metal-free catalysts offer intrinsic advantages over metal catalysts, including lower cost, higher
abundance, corrosion resistance, and eliminatIion of metal leaching, making them highly attractive
for large-scale, sustainable H O production. Over the past decade, extensive efforts have
2 2
identified a variety of active motifs in carbon-based materials capable of promoting the 2e⁻ ORR.
These include edge carbon atoms with unsaturated coordination,11,12 intrinsic defect sites such as
vacancies and topological distortions,13,14 and heteroatom-doped configurations15-17 that modulate
local electronic structures. Such sites can generate localized charge or spin densities favorable for
OOH* adsorption, enabling selective H O formation. Despite these advances, a fundamental
2 2
challenge persists in metal-free carbon catalysts: the poor controllability of defect states. Especially,
the heteroatom-doped carbon catalysts exhibit significant atomic heterogeneity due to diverse
dopant motifs and random defects, making it challenging to correlate structure with catalytic
performance. Although heteroatom-induced defects (e.g., pyrrolic N, pyridinic N, and dangling
bonds) are widely recognized as active sites, the catalytic role of these defects under the influences
of secondary heteroatom doping and partial defect passivation remained poorly understood.3,17
Achieving defect passivation typically requires restoring sp2 conjugation or incorporating
heteroatoms that terminate defect states; however, perfect carbons often display poor 2e⁻ ORR
activity, and excessive heteroatom doping may introduce new defects rather than passivate existing
ones.18 Elements with multiple bonding configurations could enable defect passivation,19,20 while
likely preserving catalytic activity towards 2e⁻ ORR. Beyond activity, stability is equally critical
for practical H O production, as edge defects with high local electron density are prone to
2 2
hydroxyl radical (•OH) attack, leading to performance decay.21 Transferring the local high electron
density to more stable sites and terminating the dangling bondsS can enhance the chemical stability
and reduce the tendency to be attacked, and finally Rincrease the stability. From this defect-
engineering perspective, fluorine (F) emerges as a r ational yet underexplored choice.
As the most electronegative element, F fIorms multi-bonding states and exhibits pronounced
electron-withdrawing capability, suggesting its potential to terminate unstable dangling bonds and
redistribute local charge density. Although F doping shows some potential as a conventional
electronic dopant in 2e⁻ ORR catalysts,22,23 its interaction with pre-existing defect motifs,
particularly N-related defects, has not been thoroughly studied, leading to a significant knowledge
gap in the design of metal-free catalysts. Particularly, several unresolved mechanistic questions
remain: How does F interact with different nitrogen configurations and defect states? Can F-
induced defect passivation be translated into predictable regulation of OOH* adsorption? And how
does such passivation simultaneously impact selectivity and long-term durability? Addressing
these questions is essential for establishing a unified structure–activity relationship for F-modified
carbon catalysts.
In this work, to elucidate the unclear role of defect passivation in governing catalytic activity
and stability, and to revisit the heteroatom synergism in codoped carbons, we employed fluorine
(F) modification of nitrogen-doped carbon (NC) to leverage F’s multi-bonding states for defect
passivation. We constructed 15 graphene configurations with and without defect passivation by
systematically varying N and F dopants, and performed DFT calculations on 66 potential active
sites, followed by statistical analysis to screen the optimal active sites for 2e⁻ ORR. The results
indicate that F passivation significantly reduces the free energy of OOH* (∆G ), thereby
OOH*
facilitating 2e⁻ ORR. In addition, semi-ionic F-passivated NC (NFC) achieves a ∆G of just
OOH*
0.006 eV, close to the thermodynamic optimum (∆G of 0), indicating near-ideal catalytic 2e⁻
OOH*
ORR behavior. Guided by these insights, NFC was synthesizeSd via simple annealing of a mixture
of NC and polyvinylidene fluoride (PVDF). ExperimenRtal characterizations confirm that F atoms
selectively attack N sites, passivate defects, and r edistribute local electron density, leading to a
transformation of surface charge from positiveI (NC) to negative (NFC). This electronic modulation
enhances OOH* adsorption stability and governs protonation kinetics. As a result, NFC delivers
nearly 100% H O selectivity at 0.5–0.65 V vs. RHE and >95% selectivity across 0.01–0.65 V vs.
2 2
RHE, overcoming the narrow-potential selectivity limitations seen in most catalysts (Table S7).
Furthermore, the defect-passivated NFC exhibits excellent durability, maintaining over 3x longer
stability than NC, highlighting the stabilizing effect of F-induced defect passivation. Operando
Raman spectroscopy further confirms that 2e⁻ ORR on NFC proceeds via a water-assisted, oxygen-
involved 2e⁻ ORR pathway. In practical electrolyzer tests, NFC delivers industrial-level
performance, reaching 1 A cm-2 current density and sustaining stable operation at 300 mA cm-² for
over 105 h with an average Faradaic efficiency (FE) of ~95%, alongside a high H O yield of 74.35
2 2
mol g -1 h-1. These metrics is competitive with most previously reported catalysts and
cat.
electrolyzers (Table S8). Furthermore, coupling the cathodic 2e⁻ ORR with the anodic methanol
oxidation reaction (MOR) reduces the cell voltage by 1.23 V at equivalent current density, achieves
nearly 100% H O selectivity, and boosts the production rate to 1.39 mol cm-2 h-1. Techno-
2 2
economic analysis (TEA) shows that the coupled ORR//MOR system yields 2.2x to 10.9x higher
revenue than the conventional ORR//OER process across 1.0–2.0 V, enabling a maximum annual
gross profit of $11.1 million. Together, these results systematically validate, through both statistical
screening and practical electrolyzer demonstration, that F-induced defect passivation and
synergism is a powerful strategy to enhance both the activity and stability of carbon catalysts for
industrial-scale 2e⁻ ORR and cost-effective H O electrosynthesis.

Results
1. Statistical-learning-assisted screening of configuraRtions with/without defect passivation
To evaluate the effect of defect passivation on 2e⁻ ORR, we constructed 15 graphene
configurations with and without defect passivIation by systematically varying N and F dopants, and
performed DFT calculations on 66 potential active sites (Carbon atoms at different chemical
environments, Table S1). Statistical analysis was then applied to screen the most favorable active
sites (Figure S1-5 and Table S1). As illustrated in Figure 1a, the workflow integrates three modules,
including data collection, model screening, and model evaluation, using 10 structural and
electronic descriptors (y-axis in Figure 1b, see details in Figure S1-5 and Table S1-3). For better
clarification, the statistical-learning analysis is built upon 10 local structural and electronic
descriptors that collectively capture the chemical environment of catalytic carbon sites. These
descriptors can be conceptually grouped into three categories: (i) local coordination and geometry,
including the coordination number (CN), ring type (R-T), and average C-C bond length around the
catalytic carbon site (ave. C-C), which describe defect topology and local lattice distortion; (ii)
compositional proximity descriptors, including C-neigh, N-neigh (N-N), F-neigh (F-N), as well as
the numbers of N and F atoms in the configuration, which quantify the chemical neighborhood of
the active carbon; and (iii) adsorption-related and electronic descriptors, namely the distance
between OOH* and catalytic active site (d) and the net charge on the active carbon (N-cha), which
directly reflect adsorption condition and local electronic polarization. Collectively, these 10
descriptors provide a framework to correlate defect structure, heteroatom doping, electronic
modulation, and OOH* adsorption behavior across diverse active sites.
The heatmap in Figure 1b highlights basic raw parameters across 66 constructed
configurations. A physical filter based on the adsorption distance (d ) of the OOH*
OOH*
intermediate (d >2 Å, Figure 1c) was applied to exclude non-rSeactive sites, which aims to yield a
set of potentially active configurations for further correlRation study. In addition, since the binding
strength of OOH* directly governs both the activi ty and selectivity toward H
2
O
2
, the descriptor
ΔG
OOH*
provides a functional parameter for Iconstructing the activity volcano and assessing the
relative catalytic properties of different activity sites.24 The ΔG values of filtered catalytic sites
OOH*
were further calculated by DFT calculation (Table S4). Statistical screening of the correlations
between the absolute ΔG (abs(ΔG )) was performed using Pearson, Spearman, and Kendall.
OOH* OOH*
As shown in Figure 1d, the correlation of N-neigh (neighboring nitrogen atoms around the catalytic
carbon site) shows a slight positive correlation, which means the catalytically active sites adjacent
to the doped N atoms tend to increase abs(ΔG ), which is detrimental to 2e⁻ ORR. A reduction
OOH*
in N content or a modification of the N-related sites could therefore be more favorable. In contrast,
coefficients of number of F atoms (N-F), number of N atoms (N-N), neighboring F atoms (F-neigh,
F adjacent to the active carbon atoms), ring-types (R-T, where the active C atoms are located),
coordination numbers (CN) of active sites, net charge (N-Cha) of the active carbon atoms in the
constructed configurations show negative values. Such relationships indicate that increases in
these features lead to lower abs(ΔG ), thereby promoting enhanced 2e⁻ ORR. Furthermore, as
OOH*
shown in Figure 1e, the strength of these negative correlations follows the order: N–F < F-neigh ≈
N-cha < CN < R–T < N–N, underscoring that F-doping and the presence of adjacent F atoms exert
a more pronounced effect on reducing abs(ΔG ) than the coordination environment or N
OOH*
concentration. Collectively, these findings demonstrate that the introduction of F into NC
substantially enhances 2e⁻ ORR activity, indicating that F-induced defect passivation can optimize
2e⁻ ORR. To further theoretically elucidate the positive effect of defect passivation on the catalytic
behavior, we screened a series of representative configurations and mapped the ΔG onto the
OOH*
2e⁻ ORR volcano plot (Figure 1f). Within the 2e⁻ pathway, theS thermodynamic limiting potential
U is defined as 0.70 V vs. RHE; at this potential, the oRverall free-energy barrier is zero, and the
L
theoretical overpotential is determined by the devia tion between U
L
and the equilibrium potential.
Active sites on the left flank bind OOH* too sItrongly, making the reduction/desorption step (HO
2
⁻
+ H O + 2e⁻ → 3OH⁻) rate-limiting. In contrast, those on the right flank bind OOH* too weakly,
2
so the initial activation step (* + O + H O + e⁻ → OOH* + OH⁻) becomes limiting. Thus, 2e⁻
2 2
ORR activity is governed by the OOH* binding strength at the active sites. In Figure 1f, g, pristine
carbon sites lie far from the volcano apex, indicating non-optimal OOH* binding and large
overpotentials. N-doping moves the sites closer to the center, partially optimizing adsorption,
while F-doping further shifts them toward the apex by weakening overly strong OOH* binding.
Strikingly, F-substitution at N-sites and (N, F)-co-doping-sites (Figure S6) gradually reduces the
abs(∆G ) to zero, placing the sites closer to the volcano apex, demonstrating stepwise tuning
OOH*
toward the thermodynamic ideal for 2e⁻ ORR. Notably, the NF-HHM1 site (representing a (N, F)-
codoped graphene configuration, in which the N and F dopants occupy meta-positions relative to
each other, Table S1, No.56) is almost located at the top of the volcano plot with an overpotential
of 0.006 V, which can be regarded as an ideal catalytic site for 2e⁻ ORR. As the catalytic reaction
prefers to take place on the highly active sites, we further screened the highly active sites of
different catalytic configurations, including the pristine graphene, N-doped graphene, F-doped
graphene, and (N, F)-codoped graphene, and mapped their abs(ΔG ) in Figure 1h. It shows that
OOH*
abs(ΔG )decreases monotonically from ~0.30–0.43 eV (pristine) to ~0.14–0.19 eV (N-doping),
OOH*
~0.025–0.054 eV (F-doping), and finally ~0.006–0.035 eV ((N, F)-codoping). This systematic
reduction highlights the F-induced defect passivation on NC, fine-tunes the adsorption energetics
for highly efficient and selective H O electrosynthesis. In addition, the projected density of states
2 2
(DOS) analysis reveals that optimal catalytic carbon sites exhiSbit pronounced overlap of their 2p
z
orbitals in the vicinity of the Fermi level, and partial eRlectron transfer analyses indicate that F-
induced defect passivation can significantly regulat e the electronic structure, thereby boosting the
2e⁻ ORR (Supplementary Discussion 1-2, FigIure S7-S16 and Table S5).
In essence, the statistical-learning analysis is used to extract key structure–activity insights
from a highly heterogeneous set of active sites. Rather than focusing on individual configurations
or isolated descriptors, this method identifies the types of local atomic features (e.g., F-substitution
at N-sites and (N, F)-codoping-sites) that consistently reduce abs(∆G ) across the 10
OOH*
descriptors, indicating that the F-induced defect passivation primarily governs the activity and
selectivity in the 2e⁻ ORR.

2. De-nitrogenation–fluorination cascade
To achieve highly optimized 2e⁻ ORR catalysis suggested by the Statistical-learning-assisted
screening of active sites, nitrogen-doped carbon (NC) and polyvinylidene fluoride (PVDF) were
mixed in different ratios and annealed under Ar to induce a de-nitrogenation–fluorination (De-N–
F) cascade, yielding (N, F)-codoped carbon (NFC) via F-induced defect passivation (Figure 2a).
During high-temperature annealing, PVDF undergoes dehydrofluorination, releasing reactive
hydrogen fluoride (HF),25 which attacks N-sites in NC and tunes the electronic structure of the
active sites. Thermogravimetric analysis (TGA) confirms PVDF decomposition begins above
410 °C (Figure S17), guiding the selection of annealing temperatures. NC, synthesized following
our previous work,26 acts as both the carbon support to prevent PVDF melting and as the N-source,
while PVDF provides the F-dopant to realize the De-N–F cascade. X-ray diffraction (XRD)
patterns of the resulting materials (Figure S18) display the characteristic carbon (002) and (101)
reflections at ~25.2° and 43.7°,27 with no PVDF-related peaks, confirming complete PVDF
decomposition. Elemental analysis (Figure 2b) reveals a graduSal decrease in N content from 2.56
at.% (NC), 1.62 at.% (NFC ), 1.18 at.% (NFC) to R0 at.% (FC) as PVDF loading increases,
control
while F content increases from 0 at.% (NC) to 5.03 at.% (NFC
control
), 7.55 at.% (NFC), and 11.1%
(FC), respectively. At a 1:1 NC/PVDF ratio (FIC sample), N is completely removed, and F content
reaches its maximum, indicating aggressive interaction of F atoms with N-sites during annealing,
leading to the elimination of N and the simultaneous incorporation of F dopant. Moreover, F
incorporation is highly temperature-sensitive: at a 1:1 NC/PVDF ratio (Figure S19g), F content
decreases from 11.1 at.% (500 °C) to 3.75 at.% (600 °C) and completely vanishes at 700 °C
(NFC600-1/1 and NFC700-1/1 samples are named as FC2 and Blank-C, respectively, Figure S20),
consistent with enhanced dehydrofluorination at elevated temperatures.28
DFT calculations of the formation energy of different N- or F-containing configurations were
performed to further understand the De-nitrogenation–fluorination process (Figure 2c). Notably,
the formation energy for F attacking graphite-N (F-A-Gra-N) is as high as 5.68 eV. While the
formation energies for F attacking two pyridinic-N sites (F-A-Pyri-N-1, or F-A-Pyri-N-2) and one
pyrrolic-N site (F-A-Pyrr-N) are 2.71 eV, 0.18 eV, and –1.45 eV, respectively, indicating that
pyrrolic-N sites are considerably more susceptible to F compared to pyridinic-N. This result
indicates that three N-species follow the stability order: graphite-N > pyridinic-N > pyrrolic-N.
The stability order can be explained as follows. Pyridinic-N is incorporated in a six-membered
ring and well matched to the graphene lattice; its lone pair occupies a sp2 orbital in the ring plane
and does not contribute to the π system, enabling a rigid sp2 framework with stronger C–N bonding.
By contrast, pyrrolic-N resides in a five-membered ring that imposes intrinsic topological strain;
its lone-pair electrons participate in the π-conjugated system, which redistributes electron density,
weakens the σ C–N bonds, and creates a chemically vulnerable, electron-rich defect motif. As a
result, pyrrolic-N is energetically more prone to being attackeSd and reconstructed, making it the
most susceptible N species during F-induced defect pasRsivation, while pyridinic-N and especially
graphitic-N embedded in a more rigid sp2 network are comparatively stable.
Further experimental characterizations, Iincluding X-ray Photoelectron Spectroscopy (XPS)
and X-ray Absorption Near-Edge Structure (XANES), were performed to confirm the stability
order of the three N species during the De-nitrogenation–fluorination process. The fitting residuals
of the N 1s XPS spectra of NFC, NC, and NFC are narrowly distributed around zero across
control
the pyrrolic-N, pyridinic- and graphitic-N regions (Figure S21), confirming the well-adapted XPS
deconvolution. The relative content of graphite-N gradually increases, while the pyridinic-N and
pyrrolic-N decrease (Figure 2d and Figure S22), confirming that graphitic-N sites are least affected.
Further absolute content of N species shows the reduced content of N species after F attacking,
following the order of graphite-N < pyridinic-N < pyrrolic-N (Figure 2e and Figure S23), which
indicates that pyrrolic-N exhibits the largest loss, followed by pyridinic-N, with minimal removal
of graphitic-N, consistent with the DFT-predicted stability order. Furthermore, as shown in Figure
S24, the differential N K-edge spectra reveal a pronounced attenuation of pyrrolic-N after
enhanced fluorination (NFC vs. NFC ), whereas the changes in pyridinic-N are much weaker
control
and the graphitic-N region remains largely intact. This directly confirms that F preferentially
perturbs unstable pyrrolic-N rather than uniformly removing all N species, and also reveals the
preferential vulnerability of graphite-N < pyridinic-N < pyrrolic-N (corresponding stability order:
graphite-N > pyridinic-N > pyrrolic-N). These results demonstrate that the De-N–F cascade arises
from F preferentially attacking pyrrolic- and pyridinic-N, leading to N removal and simultaneous
F incorporation into the carbon lattice. Moreover, both pyridinic- and pyrrolic-N peaks in NFC
exhibit positive binding energy shifts of ~0.2 eV and ~0.1 eV, respectively (Figure 2d), indicating
the electron density depletion at N-sites caused by the strongS electron-withdrawing nature of F-
dopants.
The morphologies of NC, FC, NFC, and Blan k-C (without N or F doping) were confirmed
by scanning electron microscopy (SEM) to coInsist of small nanoparticles (NPs, Figure S25). SEM,
Transmission Electron Microscopy (TEM), and High-Angle Annular Dark-Field Scanning
Transmission Electron Microscopy (HAADF-STEM) images (Figure 2f-k) reveal a uniform
distribution of N and F elements across the NPs. Furthermore, the high-resolution STEM in Figure
1l shows irregular carbon fringes in NFC, indicating abundant surface defects, whereas NC
exhibits more ordered carbon fringes (Figure S26). Additionally, contact angle measurements
(Figure S27) show that F-containing carbons (FC and NFC) become more hydrophobic, with
contact angles increasing relative to NC. For example, NFC exhibits a contact angle of 149°
compared to 125.3° for NC, an effect attributed to the incorporation of hydrophobic F atoms.
This enhanced hydrophobicity is beneficial for establishing robust triple-phase interfaces (TPIs), which
is beneficial for catalytic reactions such as 2e⁻ ORR.29

3. Structural modification and F-induced defect passivation
The structural modification of NC, NFC, and FC was further analyzed to understand the
synergy between doped N and F atoms. As shown in Figure 3a, NC (black line) exhibits the
strongest π* peak corresponding to C 1s → π* antibonding orbital transition that serves as a
characteristic spectral feature of sp2-hybridized carbon structures,30 indicating the preservation of
a well-developed π-conjugated structure. As the F content increases from NFC to NFC and
control
then to FC, the π* peak progressively weakens and broadens, indicating disruption of the sp²
carbon network and reduced π-electron delocalization caused by F-doping, leading to partial
degradation of long-range π-conjugation. Meanwhile, the Sσ* peak located around 292 eV
originates from the C 1s → σ* transition and serves as aR spectral signature of C-C single bonds in
the carbon framework. Compared to NC, the σ* peak intensity decreases slightly in the other
samples, particularly in FC, suggesting that tIhe carbon network undergoes partial reconstruction
or localized structural disorder upon F-doping. Due to its high electronegativity, F forms polar
semi-ionic C–F bonds (Figure 3b-c),31 which perturb local sp2 conjugation, promote electron
localization, and attenuate both π* and σ* features. As revealed by F K-edge (Figure 3b), the
samples exhibit a prominent π* transition at ~689 eV, while the σ* transition near ~696 eV remains
weak,32 confirming that F predominantly forms semi-ionic C-F bonds with sp2 carbon, rather than
covalent C-F bonds that would convert carbon atoms to sp3 hybridization.
Notably, semi-ionic C–F bonds (Figure 3b-c) effectively passivate carbon defects responsible
for activating the D band in Raman spectra. Raman analysis (Figure S28) shows that all fluorinated
carbons display characteristic D (~1350 cm⁻¹) and G (~1580 cm⁻¹) bands, confirming sp² carbon
structures with defects.33 However, the I /I ratio progressively decreases with increasing F
D G
content (and concomitant N depletion, Figure 3d), indicating fewer defect-induced A g breathing
1
vibrations. This reduction can be attributed to two factors: First, the formation of semi-ionic C-F
passivates edge defects without introducing topological disorder, thereby reducing the number of
vibrationally active defect sites. Second, XPS and N K-edge (Figure 3e) reveal a substantial loss
of pyridinic N and pyrrolic N upon F doping,34 which typically reside at edge or defect sites and
enhance the D band intensity by breaking local symmetry and inducing electronic disorder. They
therefore contribute to the overall suppression of D band resonance. Post-annealing experiments
provide direct validation (Figure S19 and S29): when F content is reduced from 11.05 at.% (FC)
to 3.59 at.% (FC2) and finally to 0 at.% (Blank-C), I /I correspondingly increases, fully
D G
recovering to 0.980 after complete F removal. This trend coSnfirms that semi-ionic C–F bonds
suppress D-band activation by defect passivation rather Rthan by sp3-type disorder. Furthermore, F-
doping exhibits a stronger influence on I
D
/I
G
than N-doping, highlighting its dominant role in
structural modulation of NFCs (SupplementaIry Discussion 3 and Figure S30).
Zeta potential (ZP) was employed to further clarify the effects of F-induced defect-passivation
on the global surface charge evolution. The ZPs of NC, FC, NFC, and NFC were measured to
control
be +37.6 mV, −48.6 mV, −42 mV, and −24.1 mV, respectively (Figure 3f-g). Defect-passivation
of F shifts the ZPs from positive to negative, indicating a transition of the surface from electron-
deficient (electropositive) to electron-rich (electronegative). This shift directly influences oxygen
protonation and OOH* adsorption stability, thereby modulating the selectivity of the 2e⁻ ORR
pathway.35 Notably, excessive electron enrichment in FC (lowest ZP of −48.6 mV), while favoring
OOH* adsorption, hinders its desorption and limits 2e⁻ ORR activity.36 In addition, we also
analyzed the local electronic modulation using the Bader charge (Table S6). Regarding N-doped
configurations, the Bader analysis reveals pronounced charge polarization: N atoms carry
substantial negative charge (−0.95 to −1.29 e), while the catalytically relevant carbon atoms exhibit
strong positive charges (+0.327 to +0.676 e), indicating highly electron-deficient carbons. Upon F
incorporation, F atoms consistently act as strong electron-withdrawing centers (−0.627 to −0.680
e), which results in the positive charge reduction of the catalytically relevant carbon atoms. For
example, the Bader charge of those carbon atoms in the F-doped configurations (+ 0.278 to + 0.372
e) and (N, F)-codoped configurations (+0.297 to +0.495 e) is reduced compared to that of the N-
doped configurations (+0.327 to +0.676 e). Therefore, F incorporation into NC provides
microscopic evidence that the local electronic environment of different configurations is
fundamentally altered, which regulates the OOH* adsorption and the reaction selectivity. In
addition, the microscopic charge-state reversal can change the Ssurface adsorption species, thereby
resulting in an apparent reversal of the global surface chRarge measured by zeta potential.
Furthermore, defect-passivation of F significa ntly modulates the electronic structures of NC.
As shown in Figure 3h-m and Figure S31-32,I the work functions (Φ) decrease from 4.49 eV (NC)
to 4.4 eV (FC) and 4.37 eV (NFC). The higher Φ of NC corresponds to a lower Fermi level and
insufficient surface electron density. In contrast, the defect-passivation of F reduces Φ, elevates
the Fermi level, and enriches surface electrons, lowering the energy barrier, facilitating electron
transfer, and enhancing ORR performance.37-40 Interestingly, Figure 3k, m reveals nanoscale low-
Φ domains embedded within a high-Φ matrix in NFC, forming lateral heterojunctions. The Φ
difference drives electron flow from low-Φ to high-Φ domains until Fermi level alignment,
generating a local in-plane built-in electric field directed from the high-Φ to the low-Φ regions,
and inducing field-guided electron channeling. The optimized performance of NFC (Figure 4a)
highlights that this field-guided electron channeling is beneficial for the 2e⁻ ORR.

4. Intrinsic electrochemical 2e⁻ ORR property
The 2e⁻ ORR performance of NC and NFCs was systematically evaluated in O -saturated 0.1
2
M KOH electrolyte. The samples of NF, FC, NFC, and NFC all exhibit distinct reductive
control
peaks (Figure S33), confirming ORR activity. Catalyst loading optimization (Figure S34)
identified 101.2 μg cm-2 as the optimal condition for three-electrode testing. Among all samples,
NFC shows the highest ring current in linear sweep voltammetry (LSV) polarization curves (Figure
4a and Figure S35), indicating better 2e⁻ ORR performance. Interestingly, F doping combined with
gradual N removal led to a decrease in disk current but a pronounced increase in ring current,
demonstrating that F-induced defect passivation effectively shifts ORR selectivity toward the 2e⁻
pathway. Consistently, NC exhibits the highest water formation current density (J ), indicating
H2O
that N-doping favors the 4e⁻ ORR pathway. In contrast, NFCS shows the lowest J with 85%
H2O
current reduction compared to the NC (Figure 4b andR Figure S36), directly demonstrating the
effective suppression of the 4e⁻ ORR pathway and the promotion of selective H
2
O
2
generation,
which confirms that F-passivation on N-dopIed samples can enhance selectivity toward the 2e⁻
pathway (More detailed discussion can be obtained in Supplementary Discussion 4). The H O
2 2
selectivity and corresponding electron transfer number were quantified across 0.01 ⁓ 0.65 V vs.
RHE (Figure 4c). NFC achieves >95% selectivity over the entire potential range and approaches
100% between 0.5–0.65 V vs. RHE, ensuring efficient H O production under practical operating
2 2
conditions. In contrast, NC exhibits only ~75% selectivity, markedly lower than both FC and NFC.
These results collectively underscore that F-induced defect passivation plays a decisive role in
promoting the 2e⁻ ORR pathway and enabling high H O selectivity.
2 2
Additionally, the Tafel slope of NFC was calculated to be 62.1 mV dec-1, which is lower than
that of NC (74.0 mV dec-1) and FC (65.6 mV dec-1) (Figure 4d and Figure S37a-b), indicating that
NFC exhibits faster reaction kinetics for 2e⁻ ORR. The electrochemical active surface area (ECSA)
was estimated via the double-layer capacitance (C ) method (Figure S38), offering insights into
dl
the density of accessible active sites. To further assess intrinsic catalytic activity, the ring current
at 0.2 V vs. RHE was normalized by ECSA, using the equation: Ring current/ECSA (R/E). As
illustrated in Figure 4e, R/E of NFC exhibits the highest normalized ring current density,
approximately 2.38x greater than that of NC and FC, which demonstrates that F-induced defect
passivation generates more intrinsically active catalytic sites for the 2e⁻ ORR pathway.
Benchmarking against state-of-the-art 2e⁻ ORR catalysts using five key metrics, including working
voltage window (WVW, V), H O selectivity (Sel.%), electron transfer number (n), Tafel slope
2 2
(mV dec-1), and the voltage window over which H O selectivity exceeds 90% (VW ),
2 2 Sel.% > 90%
shows that NFC delivers competitive performance in those cateSgories (Figure S37c and Table S7),
confirming its status as a highly effective H O electrocRatalyst. Furthermore, the stability of NFC
2 2
was assessed using a gas diffusion electrode (GDE) in a three-electrode setup. NFC displays near-
steady behavior with mild activation, reaching 106.3% retention at ⁓ 82770s (Figure 4f and Figure
S39). In sharp contrast, NC decays to 78.4% by ⁓ 26,000s. This dramatic durability improvement
underscores that F-induced defect-passivation is beneficial to enhance the catalyst stability for 2e⁻
ORR. To consider practical viability and directly validate the retention of F-induced defect
passivation, post-catalytic characterizations of the NFC were performed after stability tests. As
shown in Figure S40a, the atomic percentage of N in NFC after the durability test (denoted as
NFC ) is 1.13 at.%, which is essentially unchanged compared with that of fresh NFC (1.18 at.%).
after
Moreover, the N 1s spectra and corresponding peak deconvolution (Figure S40b–c) reveal that the
overall distribution of N chemical states remains comparable before and after long-term operation,
indicating the chemical stability of the carbon framework. Additional SEM and Scanning
Transmission Electron Microscopy - Energy Dispersive X-ray Analysis (STEM-EDX)
characterization of NFC confirms a uniform elemental distribution (Figure S40d and Figure
after
S41a). Furthermore, HRTEM images (Figure S40e–f) show well-defined carbon fringes without
noticeable structural collapse or severe amorphization, demonstrating that the carbon framework
is well preserved after the stability tests. Consistently, Raman spectra show that NFC maintains
after
an essentially unchanged defect signature, with I /I = 0.951 (Figure S41b), very close to that of
D G
pristine NFC (I /I ≈ 0.95), indicating that the overall defect/graphitic balance is retained after
D G
long-term operation. In addition, the stability of the (N, F)-codoped configurations was further
evaluated by the variations between time and energy in molecular dynamics simulations. The
100
stability score can be calculated by S = , where D
rel
,S V
rel
, and J
norm
represent relative
1+Drel+Vrel+Jnorm
drift, variability relative to range, and short-term jitter, respEectively (Detailed calculations can be
obtained in Supplementary Information: 3.1. StabilityP analysis for Time-Energy trajectories for ab
initio molecular dynamics). The results furNther validate this observation: (N, F)-codoped
configurations (NF-HHM, NF-HHP, NF-HH O) exhibit significantly higher stability compared to
N-only configurations (Pyri-N-LH, Pyri-N-HH, G-N) (Figure 4g-h, Figure S42, and
Supplementary Video S1-S6), confirming that F incorporation enhances the structural robustness
of active sites.
From the comparative study of NC, NFCs, and FC, F doping, confirmed as defect passivation,
clearly enhances 2e⁻ ORR performance. To further verify this effect, we investigated the catalytic
activity of FCs (FC, FC-2, and Blank-C). XPS analysis revealed a gradual decrease in semi-ionic
C-F content with increasing temperatures, with Blank-C showing a complete loss of F and N
(Figure S20 and S29). As expected, Blank-C, lacking defect passivation, exhibited the poorest 2e⁻
ORR activity among the three samples, further reinforcing that the defect passivation plays a
crucial role in enhancing the H O production. To deconvolute the role of N-species, we correlated
2 2
average H O selectivity with the relative contents of graphitic N, pyrrolic N, and pyridinic N
2 2
(Figure 4i). The analysis reveals a perfect positive correlation with graphitic N (correlation
coefficient = +1), a strong negative correlation with pyrrolic N (≈ –0.99), and a slightly less
negative correlation with pyridinic N (≈ –0.97), establishing the activity order graphitic N >
pyridinic N > pyrrolic N, fully consistent with DFT predictions (Figure 1f-g). We further evaluated
the contribution of oxygen (O)-doping using Blank-C, which contains only O (4.7 at.%) and carbon.
Although O-doped Blank-C shows measurable 2e⁻ ORR activity, indicating a minimum
contribution of O-dopant to 2e⁻ ORR,41 increasing oxygen content from 3.78 at.% (FC) to 4.7 at.%
does not significantly enhance the ring current. In contrast, the inStroduction of N- and F-dopants
(NC, FC, FC2) markedly increases the ring current despite lower oxygen content (Figure S35),
indicating that semi-ionic F- and N-dopants, rather than O, are the dominant factors governing 2e⁻
ORR enhancement through defect passivation. The Blank-C, which contains only oxygen doping
(4.7 at.%), exhibits measurable catalytic ac tivity (ring current) toward the 2e⁻ ORR. In addition,
to further exclude the possibility thaLt enhanced 2e⁻ ORR performance originates from oxygen
content, oxidized XC72 (O-XC7I2) with a much higher oxygen concentration was employed as an
oxygen-rich control. Despite containing 16.89 at.% oxygen (Figure S43c-d), substantially higher
than that of Blank-C (4.7 at.%) and NFC (3.63 at.%), O-XC72 exhibits markedly lower H O
2 2
activity and a limited selectivity of only 35–43%, accompanied by an electron transfer number
above 3 (Figure S43a-b), indicating dominant 4e⁻ ORR behavior rather than the 2e⁻ ORR.
This
result demonstrates that increasing oxygen content alone not only fails to enhance 2e⁻ ORR
selectivity but may even be detrimental to H O production. Therefore, these observations confirm
2 2
that oxygen contributes only a baseline activity, whereas the pronounced enhancement in NFC
arises from the N dopants and F-passivation (More detailed discussion can be obtained in
Supplementary Discussion 5).

5. Catalytic mechanism of 2e⁻ ORR
To gain deeper mechanistic insights into the reaction intermediates and pathway over NFC,
operando Raman spectroscopy was performed under varying potentials to directly track surface-
adsorbed species during 2e⁻ ORR, offering valuable information about transient intermediates and
their potential-dependent evolution. A custom-built electrochemical operando Raman cell was
developed to monitor surface intermediates during ORR (Figure 5a and Figure S44). At an applied
potential of 0.9 V vs. RHE, where no appreciable ORR activity was observed, the Raman spectrum
of NFC displays only the characteristic D (~1350 cm-1) and G (~1580 cm-1) bands of carbon.
However, as the applied potential decreases below 0.7 V vs. SRHE, weak but detectable features
emerge around 1000⁓1200 cm-1 and 1530 cm-1, whRich are attributed to vibrational modes
associated with adsorbed O
2
species (O
2
*),42-44 an d surface-bound OOH* species, respectively
(Figure 5b).45 These features become more prIonounced after subtraction of the reference spectrum
recorded at 0.9 V vs. RHE (Figure 5c), confirming that OOH* formation is triggered only under
reducing conditions. In parallel, we also observe a progressive enhancement of vibrational features
associated with adsorbed H O molecules as the potential drops below 0.7 V vs. RHE.46,47 This
2
suggests that the increasingly negative surface charge density on NFC facilitates reaction-involved
interfacial, activated water adsorption (More discussion about the water adsorption can be obtained
in the Supplementary Discussion 6), likely by creating a more favorable electrostatic environment
for H O dipoles reorientation and binding to the surface. The temporal sequence of these spectral
2
changes reveals an important mechanistic detail: H O adsorption precedes OOH* formation,
2
implying that H O molecules first anchor to the catalyst surface and subsequently donate a proton
2
to O to yield OOH* under reducing conditions (Figure 5d).
2
To further understand the role of O in the formation of ORR intermediates and to confirm
2
the origin of the observed Raman signals, operando Raman spectroscopy was conducted under N -
2
saturated electrolyte conditions as a control experiment. In sharp contrast to the O -saturated
2
environment (Figure 5b-c), where characteristic peaks assigned to adsorbed O species (O *)
2 2
(1000-1200 cm-1)42-44 and OOH* (1530 cm-1) intermediates emerged with decreasing overpotential,
the Raman spectra recorded under N -saturated conditions display “no distinct intermediate-
2
related features”, regardless of the applied potential, which means that the effective H O
2
adsorption for the active oxygen reduction occurs under O -rich environments. As illustrated in
2
Figure 5e, the evolution of Raman spectra across the potential range of 0.9 V to 0.1 V vs. RHE
exhibits only the intrinsic D (~1350 cm-1) and G (~1580 cm-S1) bands of the carbon framework.
Notably, the absence of vibrational bands around 1080⁓1R200 cm-1, previously assigned to surface-
adsorbed OOH*, strongly suggests that such specie s are not generated in the absence of O
2
.
This
observation is further corroborated by subtracIting reference at 0.9 V vs. RHE (Figure 5f), revealing
negligible features corresponding to OOH*, OH-, or H O . This validates that the Raman signals
2 ads
of ORR intermediates originate specifically from electrochemical ORR and not from the
background electrolyte. The operando Raman spectroscopy under both O - and N -saturated
2 2
conditions confirms that the 2e⁻ ORR over NFC follows a water-assisted, oxygen-involved
reaction pathway. Under O -saturated conditions, the emergence of potential-dependent
2
vibrational features corresponding to H O and OOH* intermediates confirms the sequential
2 ads
adsorption of H O and O as key steps toward H O formation.
2 2 2 2

6. H O production at industrial-level current density in a three-electrode flow cell
2 2
As confirmed by rotating ring-disk electrode (RRDE) studies, NFC was identified as the
optimized 2e⁻ ORR electrocatalyst. To validate its performance under industrially relevant current
densities (>300 mA cm⁻²),48 a standard three-electrode flow-cell electrolyzer was assembled
(Figure 6a) and evaluated in 1 M KOH. NFC was spray-coated onto a gas diffusion layer (GDL)
at a loading of 0.2 mg cm-2 to serve as the working electrode (cathode), with IrO -coated nickel
2
foam and a Hg/HgO electrode used as counter and reference electrodes, respectively. H O
2 2
concentration (C ) was quantified via titration (Methods section), and Faradaic efficiency (FE)
H2O2
was calculated based on charge passed and product yield. LSV measurements at different applied
potentials (Figure 6b) reveal that NFC achieves current densities approaching 1 A cm-2, well above
the industrial benchmark of 300 mA cm-2. Chronoamperometric (CA) tests at various potentials
(Figure S45) show FEs of 100%, 100%, 99.6%, 93.5%, 99.2%, and 100% at 0.225, 0.325, 0.425,
0.525, 0.625, and 0.725 V vs. RHE, respectively (Figure 6c)S, for H O production. Notably, at
2 2
0.225 V, NFC delivers an average current density of ~0R.8 A cm-2, corresponding to a high H O
2 2
yield of 74.35 mol g
cat.
-1 h-1 (Figure 6d). Long-term stability testing at a constant current density
of 300 mA cm-2 (80% iR-compensated) demoInstrates sustained operation with ~95% FE for over
105 h (Figure 6e), highlighting the chemical robustness of NFC in the practical electrolyzer
operating under industrial-level current density. In addition, NFC also shows competitive
performance with previously reported works (Figure S46 and Table S8).15,49-59

7. 2e− ORR paired with methanol oxidation for high economic benefits
In practical H O electrosynthesis, the cathodic 2e⁻ ORR is typically paired with the oxygen
2 2
evolution reaction (OER). However, OER suffers from sluggish kinetics and a high onset potential
of 1.23 V vs. RHE,60 imposing a considerable energetic penalty. In contrast, anodic oxidation of
small organic molecules such as methanol proceeds with a much lower onset potential (~0 V vs.
RHE) and more favorable reaction thermodynamics (Figure 7a),61 suggesting that coupling 2e⁻
ORR with methanol oxidation (MOR) can reduce the overall cell voltage and energy consumption.
Figure 7b shows the experimental setup: a divided cell with 1 M KOH in both compartments,
methanol at the anode, and commercial 75 wt% PtRu/C as the anodic catalyst (Noted as
Catal.@NF in Figure 7b, NF represents nickel foam). This architecture enables simultaneous O
2
reduction to H O at the cathode and MOR at the anode. As illustrated by the LSV curves in Figure
2 2
7c, the ORR//MOR system exhibits an approximately 1.23 V positive shift relative to ORR//OER,
highlighting a pronounced reduction in cell voltage. This reduced voltage translates into
significantly improved energy efficiency at equivalent current density. Particularly, at 2.5 V,
ORR//MOR achieves a current density of 1.0 A cm-2, nearly double that of ORR//OER (0.56 A cm-
2). Chronoamperometry (CA) tests (Figures S47-48) further confirm this enhancement, with
Faradaic efficiencies (FEs) near 100% across a wide potential Srange (ORR//OER: −1.0 to −2.2 V;
ORR//MOR: −1.0 to −1.6 V; Figures S47–S48). ImpoRrtantly, ORR//MOR delivers up to 10.9x
higher average current density than ORR//OER at − 1.0 V (Figure 7d). While ORR//OER achieves
a maximum H
2
O
2
production rate of 1.16 molI cm-2 h-1 at −2.8 V (Figure S49), ORR//MOR attains
an even higher rate of 1.39 mol cm-2 h-1 at just −1.8 V (Figure S50), demonstrating optimal
productivity at significantly lower energy input. Collectively, these results highlight that coupling
ORR with MOR simultaneously boosts H O generation and minimizes energy consumption,
2 2
making it an attractive strategy for practical H O electrosynthesis.
2 2
To evaluate system viability, a techno-economic analysis (TEA), based on the global average
price and reported work,51 was conducted based on an industrially relevant electrolyzer scale,
accounting for key inputs and outputs including energy consumption ($0.05 kWh-1), methanol
($0.67 kg-1), H O production ($1.087 kg-1), K CO byproduct ($1.14 kg-1), and the assumed
2 2 2 3
system scale (500 m2 electrolyzer area with industrially relevant capital and balance-of-plant costs)
(see Supplementary Note 1 for detailed assumptions and cost breakdowns). Although both revenue
and operating cost increase with cell voltage (Figure 7f-g), the better energy efficiency of
ORR//MOR translates into substantial economic advantages. Across 1.0-2.0 V, H O -derived
2 2
revenue from ORR//MOR is 2.6-10.9x higher than that of ORR//OER (Figure 7h), indicating that
coupling with MOR not only lowers the energy threshold for H O synthesis but also mitigates
2 2
cell corrosion at high voltages. Crucially, when revenues from both H O and K CO are
2 2 2 3
considered, ORR//MOR achieves up to 12.03x higher gross profit than ORR//OER (Figure 7i),
with a maximum annual gross profit of $11.1 million at 1.4 V, 2.37x greater than that of the
uncoupled system ($4.68 million). In summary, coupling 2e⁻ ORR with thermodynamically
favorable MOR simultaneously boosts electrochemical performance, minimizes energy
consumption, and delivers a compelling economic case, repreSsenting a key step toward scalable,
cost-competitive, and sustainable H O electrosynthesisR.
2 2
Moreover, we conceptually designed a dual -function direct methanol fuel cell (DMFC) 
(Figure S51a), integrating a 2e⁻ ORR catalysIt at the cathode and a MOR catalyst at the anode, to
simultaneously enable electrical energy generation and on-site H O production. During discharge,
2 2
the NFC cathode efficiently converts O to H O with nearly 100% Faradaic efficiency over a wide
2 2 2
current range (Figure S51b). The DMFC delivers a power density exceeding 12 mW cm-2 and
achieves discharge currents above 80 mA cm-2 at a low cell voltage of 0.1 V. This dual-output
architecture introduces an electrochemical paradigm that dissolves the conventional boundary
between energy conversion and chemical synthesis, offering a decentralized strategy for the co-
generation of electricity and valuable oxidants. Unlike conventional fuel cells, which prioritize
energy generation alone, this device enhances system-level energy utilization and economic value
by concurrently producing value-added chemicals. This “energy-chemical dual-output” concept
represents a significant step toward multifunctional electrochemical energy systems and could
pave the way for future self-sustained H O production modules, particularly in decentralized or
2 2
off-grid settings.

Methods
1. Materials
Unless otherwise specified, all analytical-grade chemicals were purchased from Fisher
Scientific. Ultrapure water with a resistivity of 18.2 MΩ·cm-1 was used for preparing all solutions.
Commercial PdPt/C (75 wt% PdPt nanoparticles supported on activated carbon) obtained from
Fuel Cell Store was employed as the reference catalyst for methanol oxidation. Nafion solution
(5.0 wt%) and carbon paper (Freudenberg H23C2, Fuel Cell Store) were also supplied by Fuel Cell
Store. The PiperION anion exchange membrane (40 μm) was purchased from Versogen.

2. Synthesis of the nitrogen-doped carbon (NC) precursor
All the chemicals were used as received without any purification. The synthesis of NC was
based on our previous study.26 Typically, 3 g of XC72 was first ground for 30 min to obtain the
carbon powder; then 150 mL concentrated HNO was mixed with the carbon powder, and the
3
mixture was heated to 135℃ for 5 h. After the oxygen functionalized process, the oxygen-doped
carbon (O-XC72) is centrifuged (8000 g) and washed with plenty of water and alcohol. The
separated O-XC72 is then dried in a vacuum oven for 10 h. Then, in order to realize the nitrogen
doping, 400 mg of the intermediate O-XC72 and 2 g of melamine were mixed and ground for 30
min to obtain a uniform mixture. Then the mixture was annealed at 900 °C for 2 h under an Ar
(argon) atmosphere to get the nitrogen-doped carbon (NC).

3. Synthesis of the (N, F)-codopIed carbon (NFCs), F-doped carbons (FCs), and Blank-C
without N and F doping
All the chemicals were used as received without any purification. The synthesized NC was
mixed with varying amounts of PVDF at mass ratios of 1:1, 2:1, and 4:1 to achieve different F
contents. The resulting mixtures were then transferred to a tube furnace and annealed at 500 °C for
1 h under an Ar atmosphere to yield the materials. These products were designated as FC (NFC500-
1/1), NFC(NFC500-2/1), and NFC (NFC500-4/1), respectively. For the preparation of FCs and
control
Blank-C with different F contents, the NC and PVDF mixture at a 1:1 mass ratio was further
annealed at 600 °C (named as FC2). To completely remove the F dopant, the same NC/PVDF 1:1
mixture was annealed at 700 °C, which is named blank-C. Importantly, Blank-C does not contain
either N or F dopants.

4. Preparation and storage of electrolyte
All electrolytes were prepared using high-purity chemicals. The 0.1 M KOH solution was
prepared by dissolving 2.81 g of KOH in approximately 400 mL of ultrapure water. After complete
dissolution and cooling to room temperature, the solution was transferred to a 500 mL volumetric
flask and diluted to volume with ultrapure water. The 1.0 M KOH solution was prepared following
the same procedure using 28.06 g of anhydrous KOH and diluted to 500 mL. For the 1.0 M KOH
+ 2.0 M MeOH mixed electrolyte, 28.06 g of anhydrous KOH was first dissolved in approximately
350–400 mL of ultrapure water, followed by the addition of 40.5 mL of methanol. After thorough
mixing, the solution was transferred to a 500 mL volumetric flask and diluted to 500 mL with
ultrapure water. All solutions were thoroughly mixed and stored in sealed containers at room
temperature. The measured pH values of 0.1 M KOH, 1.0 M KOH, and 1.0 M KOH + 2.0 M
MeOH electrolytes were 13.1 ± 0.2, 13.9± 0.2, 13.8± 0.2, respectively.

5. Operando Raman test
Operando Raman measurements were performed using a Horiba LabRAM HR Evolution
Nano equipped with a 532 nm streamline laser excitation source. The electrochemical cell,
featuring a quartz window, accommodated the working electrode (the obtained catalyst), a
saturated calomel electrode (SCE) as the reference, and a platinum wire as the counter electrode.
The laser beam was focused onto the sample through the quartz window to collect the Raman
spectra. Chronoamperometry was used to apply a series of potentials to the working electrode, in
100 mV increments ranging from 0.1 V to 0.9 V vs. RHE.

6. Electrochemical RRDE measurements
The catalyst ink was prepared by dispersing 5 mg of catalyst in a mixture of 480 μL
isopropanol, 480 μL deionized water, and 40 μL of 5 wt.% Nafion solution. This suspension was
sonicated for one hour to ensure complete dispersion, after which 2.5, 5, or 10 μL of the catalyst
suspension was drop-cast onto a glassy carbon disk electrode. The corresponding loading of 2.5,
5, and 10 μL of the catalyst ink is 50.6, 101.2, and 151.8 µg cm-2, respectively. Electrochemical
characterizations, including LSV and cyclic voltammetry (CV), evaluating the intrinsic
performance in 80 mL O -saturated 0.1 M KOH, were performed on a standard three-electrode
2
rotating ring-disk electrode (RRDE) setup (PINE, AFMSRCE) controlled by a CHI 760E
electrochemical workstation at 25 °C. In this configuration, the catalyst-coated glassy carbon disk
(RRDE, 0.2475 cm2 disk area and 0.1866 cm2 Pt ring area) acted as the working electrode, a
graphite rod served as the counter electrode, and a saturated calomel electrode (SCE) functioned
as the reference electrode. The Pt ring of the RRDE was used to monitor H
2
O
2
. Before
measurements, the SCE reference electrode was calibrated in saturated KCl to verify that its
potential matched theoretical values at room temperature. All measured potentials were converted
to the reversible hydrogen electrode (RHE) scale according to V = V + 0.224 + 0.059*pH.
RHE SCE
In the three-electrode testing system, the curves were not corrected with iR compensation. All
electrochemical tests were carried out in freshly prepared N - or O -saturated 0.1 M KOH
2 2
electrolyte at room temperature (25 °C). LSV measurements were recorded from 0 V to 1.0 V vs.
RHE at a scan rate of 10 mV s-1. Throughout these LSV measurements, a potential of 1.5 V (vs.
RHE) was continuously applied to the RRDE ring to monitor H O production. The Tafel slope
2 2
was calculated from V = b*log(abs(j)), where V is the applied potential, b is the Tafel slope, and j
is the disk current density. The electrochemical surface area (ECSA) of the catalysts was estimated
from the non-Faradaic capacitive region between 1.05 and 1.15 V vs. RHE, with the double-layer
capacitance determined by plotting the current density at 1.1 V vs. RHE against the scan rate.
Finally, the H O selectivity, number of electrons transferred (n), and H O Faradaic efficiency
2 2 2 2
(FE) were calculated from the measured disk and ring currents according to standard RRDE
equations. Notably, all the LSV and CV curves were tested several times until they were stable and
overlaid to obtain reliable data.
ir
H O (%) = 200 × N (1)
2 2
N
ir+
id
n = 4 ×
id
(2)
N
ir+
id
ir
Faraday efficiency (FE) = N ×100% (3)
id
where i is the disk current, i is the ring current, and N is the collection efficiency of the RRDE
d r
(0.37).

7. XAS measurement
Soft X-ray absorption spectroscopy (XAS) was performed at Lawrence Berkeley National
Lab, Advanced Light Source, beamline 7.3.1 under ultra-high vacuum. The data presented is the
total electron yield and was processed by subtraction of a linear pre-edge line.

8. KPFM measurement
Kelvin Probe Force Microscopy (KPFM) measurements were carried out on a Park Systems
NX-10 atomic force microscope (AFM) operated in heterodyne KPFM (HD-KPFM) mode. In this
mode, an additional AC voltage is applied at a frequency corresponding to the difference between
the cantilever’s second and first eigenmode frequencies. The resulting frequency shift is detected
using two independent lock-in amplifiers. All measurements were performed under ambient
conditions in a single-pass configuration using an ACCESS-EFM cantilever (AppNano). The
absolute work function was calibrated against freshly cleaved highly oriented pyrolytic graphite
(HOPG), taken as 4.7 eV.

9. Fabrication of electrodes for electrolyzers
To create catalyst inks, a combination of NFC catalysts, 5% Nafion solution, isopropyl (IPA),
and ultrapure water was utilized in a ratio of 30 mg to 100 μL, 2 mL, and 2 mL, respectively. After
homogeneously mixing and ultrasound treatment for 120 min , the inks were employed by
sonication spraying onto Freudenberg H23C2 carbon paper (Fuel Cell Store) to create electrodes
with different mass loading.

10. Electrochemical three-electrode flow cell measurement
The evaluation of H O synthesis performance was conducted using a flow-cell electrolyzer.
2 2
The catalyst ink was sprayed onto a 1 cm2 gas diffusion layer (GDL) carbon paper (Freudenberg
H23C2, Fuel Cell Store) with a mass loading of 0.2 mg cm⁻2, which acted as the working electrode.
A nickel foam loaded with IrO
2
(0.5 mg cm-2) was used as the counter electrode, and an Hg/HgO
electrode was used as the reference. The compartments were separated by a 1 cm2 PiperION anion
exchange membrane (40 μm). Notably, the PiperION anion exchange membrane was pretreated
by immersion in 1.0 M KOH for 1 h before use. Both the cathode and anode chambers were filled
with 1 M KOH electrolyte, freshly prepared and circulated continuously at a flow rate of 5 mL min-
1 by a peristaltic pump. All experiments were conducted at 25 °C under a continuous flow of O
2
(40 mL min-1) through the cell. The electrode with 1 mg/cm2 mass loading was used for the stability
test, and the electrolyte and IrO @Ni counter electrode were replaced every 5, 10, or 25h. Notably,
2
the electrochemical measurements were performed on Pine Model AFP2. All measured potentials
were converted to the reversible hydrogen electrode (RHE) scale according to V = V +
RHE Hg/HgO
0.098 + 0.059*pH.
The amount of H O produced in the electrolyte was quantified by a cerium (IV) titration
2 2
method. Briefly, electrolyte samples were collected, neutralized, and titrated with Ce4+ according
to the reaction: Ce4+ + H O → 2Ce3+ + 2H+ + O . The concentration of Ce4+ was determined by
2 2 2
measuring the absorbance at 317 nm. The corresponding H O Faradaic efficiency was calculated
2 2
according to the following equation:
2×VCF
FE (H O , %) = (4)
2 2
Q
where C is the concentration of the H O ; V is the electrode volume; F is the Faraday constant
2 2
(96485 C mol-1), and Q is the applied charge during the electrolysis.

11. Electrochemical two-electrode flow cell measurement
Regarding the uncoupled ORR//OER system, the catalyst ink was sprayed onto a 1 cm2 gas
diffusion layer (GDL) carbon paper (Freudenberg H23C2, Fuel Cell) with a mass loading of
0.6 mg cm⁻2, which acted as the working electrode. A nickel foam loaded with IrO was used as
2
the counter electrode. The compartments were separated by a 1 cm2 PiperION Anion Exchange
Membrane (40 μm). Both the cathode and anode chambers were filled with 1 M KOH electrolyte,
freshly prepared and circulated continuously at a flow rate of 5 mL min-1 by a peristaltic pump. All
experiments were conducted at 25 °C under a continuous flow of O
2
(40 mL min-1) through the
cell. The amount of H O produced in the electrolyte was quantified by a cerium (IV) titration
2 2
method. The Faradaic efficiency for H O was determined using the same procedure as in the H-
2 2
type cell. Briefly, electrolyte samples were collected, neutralized, and titrated with Ce4+ according
to the reaction: Ce4+ + H O → 2Ce3+ + 2H+ + O .
2 2 2
Regarding the coupled ORR//MOR system, the catalyst ink was sprayed onto a 1 cm2 gas
diffusion layer (GDL) carbon paper (Freudenberg H23C2, Fuel Cell Store) with a mass loading of
0.6 mg cm⁻2, which acted as the working electrode. A nickel foam loaded with 75 wt% PtRu/C
(metal loading = 6 mg cm-2) was used as the counter electrode. The compartments were separated
by a 1 cm2 PiperION Anion Exchange Membrane (40 μm). The cathode chambers were filled with
1 M KOH electrolyte, freshly prepared and circulated continuously at a flow rate of 5 mL min-1 by
a peristaltic pump. The cathode chambers were filled with 1 M KOH + 2 M MeOH electrolyte,
freshly prepared and circulated continuously at a flow rate of 5 mL min-1 by a peristaltic pump. All
experiments were conducted at 25 °C under a continuous flow of O (40 mL min-1) through the
2
cell. In the anodic chamber, MeOH is oxidized to CO , then the generated CO is absorbed by
2 2
KOH to form valuable K CO . The performance of the electrolyzer was measured by the Pine
2 3
Model AFP2.

12. Conceptually designed self-produced H O DMFC
2 2
The assembly of the self-produced H O DMFC is the same as the “Electrochemical two-
2 2
electrode flow cell”. Notably, for the self-produced H O DMFC, the production of H O comes
2 2 2 2
from the discharging of the DMFC at 75℃.

13. Quantum Mechanical Modeling Details
To investigate the atomistic and electronic structures of N-doped, F-doped, and (N, F)-
codoped electrocatalysts for 2e- ORR toward the H O production and their complexes with the
2 2
OOH* adsorbates, periodic spin-polarized density functional theory (DFT)62 was applied using
Vienna Ab Initio Simulation Package (VASP) 6.3.0 with the projector augmented‐wave (PAW)
method63-66. To mimic the working environment of the electrocatalyst, the implicit solvation model
was implemented using VASPsol67. VASPKIT 1.4.068 was used to generate VASP input files and
perform post-calculation analyses. Each computational box was designed to assume a 6 × 6 × 1
hexagonal supercell with a = b = 15 Å and c = 15 Å.
Geometry optimizations of doped graphene-based models and their adsorption complexes
were performed using the Revised Perdew–Burke–Ernzerhof (RPBE)69 exchange–correlation (XC)
functional along with the D3 empirical van der Waals correction 70,71 as well as 3 × 3 × 1
Monkhorst–Pack meshes for K-point sampling of the Brillouin zone and a cut-off energy of 500
eV for the plane-wave basis set. The convergence criterion for each geometry optimization was set
to 0.01 eV/ Å for force, and the convergence criterion for each self-consistent field (SCF) cycle
was set to 1.0 × 10–6 eV for energy. The above-mentioned dimensions of a and b were obtained
from optimizations for doped graphene catalysts and fixed for adsorption complexes. All possible
adsorption sites were given in Figures S1-S3 and Table S1. To determine whether an adsorption
was successful, the distance between the OOH* adsorbate and the adsorption site was measured,
and only complexes with a distance below 2 Å were considered successful. Vibrational analyses
were performed using the finite-displacement method (IBRIOSN = 5) implemented in VASP, from
which ZPE corrections were obtained. Projected density of states (PDOS) was calculated from
site- and orbital-projected wavefunction data in VASP and analyzed using VASPKIT. To examine
the stability of the electrode material, ab initio molecular dynamics (AIMD) simulations were
conducted at 298.15 K using an NVT ensemble with an Andersen thermostat. Each system was
sampled for 5 ps with a 1 fs time step while keeping the simulation cell fixed. Electronic-structure
settings followed those used in the static calculations. The initial equilibration segment was
excluded from analysis; the steady segment was used to assess structural and bonding stability
over time.

13.1. Formation Gibbs free energy of the OOH* intermediate
Gibbs free energy change of the first elementary step of 2e- ORR, which generates the OOH*
intermediate from gas-phase molecular oxygen (O ), liquid water (H O), and electron (e–)
2 2
* + O (g) + H O(l) + e– → OOH* + OH–(aq) (5)
2 2
was calculated as
ΔG(OOH*) = G(OOH*) + G[OH–(aq)] – G(*) – G[O (g)] – G[H O(l)] – G(e–) (6)
2 2
The computational hydrogen electrode (CHE) model from Nørskov and coworkers was used,
in which the pair of H+ and e– was in equilibrium with 1/2 H (g, 1 atm) at the standard hydrogen
2
electrode (SHE) condition (pH = 0 and U = 0 V), so that
SHE
G[H+(aq)] + G(e–) = 1/2 G[H (g)] – eU – RTln(10)pH (7)
2 SHE
Also, the equilibrium between H+ and OH– at any condition was utilized, so that
G[H+(aq)] + G[OH–(aq)] = G[H O(l)] (8)
2
By plugging Eqs. (7) and (8) into Eq. (6), the Gibbs free energy change for (5) became
ΔG(OOH*) = G(OOH*) – G(*) – G[O (g)] – 1/2 G[H (g)] + eU + RTln(10)*pH (9)
2 2 SHE
For each species, the Gibbs free energy was calculated as
G = E – k Tlnq + k T (10)
elec B B
where E
elec
is the ground state electronic energy, T is the absolute temperature in Kelvin, k
B
is the
Boltzmann constant, and Rq is the total molecular partition function, which includes translational,
rotational, and vibrational degrees of freedom for a gas-phase molecule (g) or vibrational degrees
of freedom for the OOH* adsorbate. G[O (g)] and G[H (g)] were evaluated at 1 atm and 298.15
2 2
K and given in Table S9. ΔG were evaluated at 298.15 K, U = – 0.70 V to reflect the applied
OOH* SHE
potential for the 2e- ORR toward H O formation under alkaline conditions (pH = 13). From this
2 2
data, we found that pristine and defect-containing graphene without N or F doping scarcely
stabilizes OOH*, with adsorption energies far above zero. N doping introduces adsorption on one
or two C atoms adjacent to N, but these sites generally overbind, except for the C atom directly
bonded to Graphitic-N, which approaches thermoneutral binding and may divert the reaction
toward a four-electron pathway. By contrast, F doping, alone or in combination with N, localizes
all active sites to C atoms neighboring F, delivering ΔG values consistently near zero,
OOH*
indicative of optimal 2e- ORR activity.

13.2. Bond lengths for stability distinction between ionic and semi-ionic C–F bonds
Upon structural optimization, two distinct types of C–F bonds were identified in the
fluorinated graphene systems (Figure S4-S5). Bonds with lengths of approximately 1.50 Å
correspond to ionic C–F interactions, which are thermodynamically unstable, prone to hydrolysis,
and rarely observed in experimental characterizations due to the absence of a significant C–F ionic
peak in XPS spectra. In contrast, bonds with lengths around 1.36 Å are characteristic of semi-ionic
C–F bonds, which exhibit enhanced stability and are consistent with experimental evidence
showing that C–F bonding in such systems predominantly exists in a semi-ionic form. Therefore,
in subsequent OOH* adsorption energy calculations, only the configurations containing semi-ionic
C–F bonds are considered, while those involving ionic C–F bonds are excluded from further
analysis. This selection ensures that the computational models reflect the experimentally relevant
bonding environment, thereby improving the reliability and interpretability of the calculated
reaction energetics.

13.3. Fluorination feasibility of nitrogen-doped carbons
A series of Gibbs free energy calculations was performed to evaluate the fluorination
feasibility on N-doped graphene configurations. The fluorination reaction was modeled as a
thermodynamic process in which hydrogen fluoride (HF) attacks different active sites with or
without molecular hydrogen (1/2 H ).
2
In the case of a bridge *C–N–C* site, the N atom was detached as ammonia (NH ) and
3
replaced by H and F atoms separately,
*C–N–C* + 3/2 H (g) + HF(g) → *C–F + *C–H + NH (g) (11)
2 3
The Gibbs free energies of HF and NH were computed using Eq. (11) and given in Table S9,
3
and the Gibbs free energy changes for Eq. (11) (ΔG ) were calculated and presented in Table S10.
flu
From these data, we found that the fluorination reactivity follows the order pyrrolic N (ΔG =
flu
−1.45 eV) > pyridinic N (+0.18 eV and +2.71) ≫ graphitic N (+5.68 eV), indicating that the local
electronic environment and available lone-pair electrons in pyrrolic and pyridinic sites facilitate F
adsorption, whereas the delocalized electronic structure of graphitic N renders fluorination
thermodynamically unfavorable.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This manuscript presents a systematic integration of theoretical calculations, material design, in situ characterization, and device validation, demonstrating the considerable potential of fluorine-doped carbon-based catalysts for highly efficient H2O2 synthesis at industrial-scale current densities. The overall study is meticulously designed and supported by a comprehensive dataset, exhibiting significant innovation, particularly in the statistical screening of active sites, the mechanism of defect passivation, and the analysis of electrolyzer performance and techno-economic viability. I recommend it to be acceptable in Nature Communication with a minor correction. The detailed comments are listed as follows.\n1. It is well-documented in the literature that other non-metal elements (e.g., P, B, S) as co-dopants in NC can also significantly enhance the performance of the 2e- oxygen reduction reaction (ORR) for H2O2 production (Angew. Chem. In. Ed. 2025, 137, e202503385, Angew. Chem. In. Ed. 2025, 137, e202500177). What is the decisive advantage of F-doping over other heteroatoms? what is the fundamental distinction?\n2. What is the reason for selecting PVDF as the fluorine doping agent, and what are its specific merits over alternative fluorine sources?\n3. The DFT calculations indicate that F preferentially attacks and removes unstable pyrrolic and pyridinic N species. Does this imply that the primary role of F is confined to \"defect passivation\" or the newly formed C-F/N-F sites as another active centers?\n4. In another paper (10.1038/s41467-023-40118-y) introduces a high-proportion pyrrole nitrogen-doped graphene mesoporous carbon composite material for improving the performance of H2O2. However, in Figure 4j of this manuscript demonstrates a positive correlation between H2O2 selectivity and graphitic N content, alongside a negative correlation with pyrrolic and pyridinic N. This conclusion appears to be in direct contrast with findings reported in other established literature.\n5. To consider practical viability, some post-catalytic characterization of the catalyst should be performed after Stability test. For example, XPS, the content of F and N, SEM?\n6. After the electrolyser has been in use for 105 hours. Was there any specific drop of yield after that?", "reviewer_2": "In this study, the authors aimed to systematically design and screen active sites on N-doped carbons using F-doping, supported by statistical analysis, DFT calculations, and operando experiments. They found that fluorine-induced defect passivation optimizes OOH* binding and enables N,F co-doped carbon to achieve nearly 100% H₂O₂ selectivity, high current densities, and long-term stable H₂O₂ production in an electrolyzer. Coupling the 2e⁻ ORR with methanol oxidation further reduces the cell voltage and greatly improves productivity, demonstrating a practical and economically favorable route for scalable H₂O₂ electrosynthesis. Here, I mainly evaluate the theoretical calculation aspects of this manuscript. I did not identify major issues in their calculations, and the results and discussion appear scientifically sound. However, there are several points that require clarification, as listed below.\n1. In lines 120-121, the authors state that \"A physical filter based on the adsorption distance (dOOH*) of OOH* intermediate (d >2 Å, Figure 1c) was ...\" It is unclear how the threshold of 2 Å was determined.\n2. The authors should check the validity of the sentence \"While the formation energies for F attacking pyridinic-N (F-A-Pyri-N) and pyrrolic-N (F-A-Pyrr-N) are 2.71 eV and 0.18 eV (or –1.45 eV), respectively,...\" in lines 197-199, because the content appears to be inconsistent with Fig. 2c.\n3. Also, the expression \"The optimized performance of NFC (Figure 4a) highlights\" in lines 277-278 may not be correct. It is unclear to me which figure the authors intended to cite.\n4. The authors should clarify how the \"stability score\" shown in Fig. 4i is defined.", "reviewer_3": "The manuscript presents a comprehensive study integrating statistical learning, theoretical calculation, materials synthesis, operando spectroscopy, and electrolyzer testing to investigate fluorine-induced defect passivation in nitrogen-doped carbons for selective 2e− ORR toward H2O2 production. The work has potential significance for both mechanistic understanding and practical electrosynthesis. However, despite the strengths, several aspects of the manuscript require substantial revision. Firstly, the central claim regarding “F-induced defect passivation as the dominant factor governing activity and stability” is not yet fully supported by the current set of evidence. The statistical-learning framework, although interesting, is complex and at times insufficiently validated experimentally, which weakens the connection between theoretical screening and real catalyst behavior. Secondly, several mechanistic interpretations, particularly those related to Raman assignment of OOH* species, surface charge reversal, and the proposed built-in electric field, need clearer justification and additional controls. Finally, the techno-economic analysis relies heavily on assumptions that should be more explicitly stated, discussed, and critically assessed.\nOverall, the manuscript contains many promising elements, but the mechanistic claims, data interpretation, and contextual analysis require deeper clarification and additional experimental or analytical support. Addressing these issues will substantially enhance the scientific rigor and persuasiveness of the work. Therefore, this reviewer believes the work does not meet the high standards of Nature Communications, particularly regarding material design and catalytic mechanism. This manuscript cannot be considered for publication in Nature Communications. The detailed comments are as follows.\n1. The Introduction should be more concise and logically structured. Although the current background section contains substantial information, it does not sufficiently contextualize prior knowledge or clarify the remaining gaps. Numerous sites on carbon materials, including edge carbons (Angew. Chem. Int. Ed. 2019, 58, 1100-1105; Adv. Funct. Mater. 2023, 33, 2305795), intrinsic defects (J. Am. Chem. Soc. 2023, 145, 21, 11589-11598; J. Phys. Chem. Lett. 2022, 13, 8914-8920), and heteroatom-doped sites (Nat. Commun. 2021, 12, 4225; Adv. Energy Mater. 2024, 2304418; Nat. Commun. 2023, 14, 4430), have already been identified as potential active sites for the 2e− ORR. These points should be incorporated into the discussion. In addition, the use of F-doped carbon in the 2e− ORR is not new (Angew. Chem. Int. Ed. 2025, 64, e202503626; Adv. Mater. 2023, 35, 2208533). Given this situation, I recommend that the authors reorganize and strengthen the introduction to better articulate the novelty of this work. The discussion should clearly progress from the challenge of poorly controlled defect states in metal-free carbon, to the rationale behind fluorine-induced defect passivation, and finally to how this study addresses unresolved mechanistic questions and fills the existing knowledge gap.\n2. The statistical-learning section would benefit from clearer summarization. Figure 1 contains many descriptors and correlation analyses. A more intuitive explanatory paragraph in the main text would help readers grasp the key structure–activity insights without frequent consultation of supplementary tables.\n3. The discussion of F attacking different N species could be expanded. Figure 2c suggests that pyrrolic-N is most vulnerable, yet the experimental validation is relatively brief. Additional spectral evidence (e.g., fitting residuals of N 1s or differential N K-edge spectra) would strengthen the conclusion.\n4. The peak assignments in the Raman spectra require support from appropriate literature or reference databases. In addition, previous studies indicate that an adsorbed O2 species typically exhibits a characteristic band within the range of 1000 to 1200 cm-1 (Nano Lett. 2024, 24, 1650-1659; Adv. Mater. 2025, 2415712; Nat. Commun. 2024, 15, 983). Therefore, it is not appropriate to attribute all features in this region solely to the OOH* intermediate.\n5. The zeta-potential discussion should distinguish global surface charge from local electronic modulation. The observed shift from positive to negative charge is described qualitatively. Incorporating DOS or Bader charge comparison between NC and NFC would more rigorously support the claim of charge-state reversal and its influence on selectivity.\n6. Normalizing activity using ECSA (Figure 4e) requires clarification of its validity. The double-layer capacitance of carbon materials does not necessarily correlate with the density of intrinsic active sites, particularly because fluorine doping may change the hydrophilicity or hydrophobicity of the surface and thus alter the measured ECSA. A brief explanation of the rationale for using Cdl as a proxy, along with its limitations, would improve the scientific rigor of the analysis.\n7. Post-stability structural characterizations are encouraged. After long-term operation (Figure 4g), XPS, Raman, or TEM analyses of the used NFC catalyst would directly validate the retention of F-induced defect passivation.\n8. Key techno-economic assumptions should be explicitly summarized in the main text. Although details are in the Supplementary Information, the economic analysis would be clearer if electricity cost, methanol price, and system-scale assumptions were briefly stated.\n9. Based on the RRDE-derived LSV curves (Figure 4a) and the corresponding H2O2 selectivity (Figure 4c), the improvement gained from fluorine doping (NFC) appears minimal, and the enhancement over the NC sample is not clearly demonstrated. This weak correlation with the authors' theoretical predictions reduces the overall persuasiveness of the work.\nSome minor comments:\n1. Consistency of notation and symbols across figures should be improved. Some abbreviations (e.g., ORR//MOR vs ORR//OER) differ slightly in formatting across figures, and ΔGOOH* appears with inconsistent styling. Unifying these will improve clarity and professionalism.\n2. The conclusion could more clearly highlight the methodological contribution. Beyond material development, the combined use of statistical learning, DFT calculations, operando spectroscopy, and flow-cell validation forms an integrated framework that can be applied to other catalytic systems. Explicitly emphasizing this transferable aspect would strengthen the overall impact of the work.", "reviewer_4": "This manuscript, entitled “From Active-Site Design to Electrolyzer Innovation: F-Modified Metal-Free Catalysts Drive H₂O₂ Electrosynthesis at Industrial-Scale Current Density,” presents an innovative approach by employing statistical learning to screen active sites for the two-electron oxygen reduction reaction. The proposed regulatory mechanism is substantiated through experimental characterization, in situ spectroscopy, and theoretical calculations. The optimized catalyst exhibits outstanding catalytic activity and stability in a three-electrode flow cell, achieving state-of-the-art performance. However, revisions are needed before the manuscript can be considered suitable for publication in Nature Communications.\n1. While the study focuses on the effects of nitrogen and fluorine doping in carbon-based catalysts, Figure S19 reveals a significant oxygen content in the samples. Given that oxygen-doped carbon materials are well-established as effective 2e⁻–ORR catalysts—with numerous studies demonstrating their high activity in alkaline media—and Supplementary Figure S33 shows that Blank-C (containing only oxygen dopants) displays activity and selectivity comparable to the NFC sample, it is essential to include control experiments that conclusively rule out the contribution of oxygen to the catalytic performance.\n2. The manuscript posits that spectral changes in Figure 5c support a reaction mechanism in which H₂O adsorption precedes OOH formation. This suggests that water molecules first adsorb onto the catalyst surface before transferring protons to O₂, leading to OOH generation under reducing conditions. However, this interpretation appears inconsistent with the absence of H₂O adsorption peaks under nitrogen-saturated conditions in Figure 5g. Further clarification is needed to resolve this discrepancy.\n3. Was any change in internal resistance during stability testing taken into account when applying iR compensation?\n4. In the RRDE performance radar chart, are H₂O₂ selectivity and the number of electron transfers fundamentally distinct performance metrics? Please clarify whether these parameters provide complementary or redundant information."}, "author_response": "Responses to the reviewers’ comments:\nTo Reviewer #1:\nThis manuscript presents a systematic integration of theoretical calculations, material design, in\nsitu characterization, and device validation, demonstrating the considerable potential of fluorine-\ndoped carbon-based catalysts for highly efficient H O synthesis at industrial-scale current\n2 2\ndensities. The overall study is meticulously designed and supported by a comprehensive dataset,\nexhibiting significant innovation, particularly in the statistical screening of active sites, the\nmechanism of defect passivation, and the analysis of electrolyzer performance and techno-\neconomic viability. I recommend it to be acceptable in Nature Communication with a minor\ncorrection. The detailed comments are listed as follows.\nResponse: We thank the reviewer for the very positive evaluation of our work and the strong\nsupport for the publication of this manuscript. We have carefully considered and addressed the\nreviewer’s comments in the revised manuscript. We hope that the revisions made to the manuscript\nwill adequately address the reviewer’s concerns and meet the publication requirements.\n1. It is well-documented in the literature that other non-metal elements (e.g., P, B, S) as co-dopants\nin NC can also significantly enhance the performance of the 2e- oxygen reduction reaction (ORR)\nfor H O production (Angew. Chem. In. Ed. 2025, 137, e202503385, Angew. Chem. In. Ed. 2025,\n2 2\n137, e202500177). What is the decisive advantage of F-doping over other heteroatoms? what is\nthe fundamental distinction?\nResponse: We sincerely thank the reviewer for the insightful comment. Compared with recent\nstudies employing other non-metal dopants, such as P, B, and, S, which also play beneficial roles\nin modulating the 2e– ORR by raising local pH levels (Angew. Chem. In. Ed. 2025, 137,\ne202500177) and optimizing the adsorption configuration of reactants and intermediates (Angew.\nChem. In. Ed. 2025, 137, e202503385), F doping in our manuscript offers two decisive and\nfundamentally distinct advantages that are not achievable with other non-metal heteroatoms.\n(a) The decisive advantage of F-doping over other heteroatoms\nR-1\nAs claimed in our manuscript, F uniquely induces defect passivation via semi-ionic C–F\nbonds, which is barely highlighted in P, B, or S doping carbons. In addition, most heteroatoms (P,\nB, S) create additional electronic disorder in carbon, often introducing new defect states (Angew.\nChem. In. Ed. 2025, 137, e202500177). In contrast, the XPS, Raman, and XANES results show\nthat F-induced semi-ionic C–F bonds can suppress D-band activation by restoring local sp2\nconjugation while avoiding sp3 carbon formation, thereby resulting in defect-passivation rather\nthan defect-activation. This selective defect-passivation without structural disruption is a unique\nchemical behavior of F.\n(b) The fundamental distinction\nGiven that F possesses the highest electronegativity among all non-metal dopants (F: 3.98)\ncompared to N (3.04), S (2.58), P (2.19), and B (2.04), F introduces a substantially stronger\nelectron-withdrawing effect. This allows the formation of semi-ionic C–F bonds and enables\nunique defect-passivation behavior that cannot be achieved by P-, B-, or S-doping. In contrast, P-,\nB-, and S-doping typically introduce additional electronic disorder due to their lower\nelectronegativity and larger atomic radii, which perturb the sp2 carbon lattice, generate new defect\nstates, or broaden electronic inhomogeneity. These dopants modulate electronic structure but\ncannot remove or neutralize pre-existing defect states. F is the dopant capable of simultaneously\n(i) passivating pyrrolic/pyridinic defects, (ii) restoring local sp2 conjugation, (iii) reducing\nabs(ΔG ) toward the thermodynamic optimum, and (iv) generating strong in-plane electric\nOOH*\nfields through Φ-heterojunction formation. Therefore, the decisive and intrinsic distinction is that\nF-doping removes detrimental defects and optimizes the electronic structure, whereas P-, B-, and\nS-doping mainly rearrange or introduce defects without enabling true passivation.\nIn the revised manuscript, we added two citations, ref[7] and ref[8], to highlight the decisive\nadvantage of F-doping and its corresponding fundamental distinction over other heteroatoms.\n2. What is the reason for selecting PVDF as the fluorine doping agent, and what are its specific\nmerits over alternative fluorine sources?\nResponse: We appreciate the reviewer’s meaningful comment. PVDF was deliberately selected as\nthe F source because its chemical behavior under thermal treatment uniquely aligns with the\nR-2\nrational defect-passivation, which cannot be equivalently achieved using other commonly used F\nsources such as PTFE or NH F. The specific merits of PVDF over alternative F sources are\n4\ndiscussed as follows.\n(a) PVDF undergoes dehydrofluorination upon thermal treatment, with F species release at\nelevated temperatures, which enables moderate interaction between F species and the defect-rich\nN-doped carbon (NC), thereby selectively tuning the electronic structure of nitrogen-associated\nactive sites rather than excessively eliminating carbon defects. In contrast, PTFE contains a much\nhigher F mass fraction (76 wt.%) than PVDF (59.3 wt.%); this excessive F probably promotes\nover-passivation of carbon defects. In sharp contrast, NH F decomposes completely at\n4\ntemperatures below 200 °C into NH and HF, resulting in a rapid and excessive release of F species\n3\nthat aggressively attack N species or defects in NC. This uncontrolled fluorination may result in\nan unfavorable environment for achieving the optimal catalytic structure of the materials.\n(b) To experimentally validate the distinct F-induced defect passivation behaviors associated\nwith different F sources, two control samples were prepared by mixing NC with PTFE or NH F at\n4\nan identical mass ratio of 2:1, followed by annealing at 500 °C for 1 h under the same conditions\nused for NFC synthesis. The resulting materials were denoted as NFC-PTFE and NFC-NH F,\n4\nrespectively. As shown in Figure R1a–b, the I /I ratios of NFC-PTFE (0.859) and NFC-NH₄F\nD G\n(0.876) are both lower than that of NFC (0.950), confirming that PTFE and NH F indeed induce\n4\nstronger defect passivation effects. More importantly, their I /I values are even lower than that of\nD G\nFC (0.924), indicating an excessive elimination of defect sites beyond the optimal regime required\nfor efficient 2e⁻ ORR.\n(c) Consistent with the structural analysis, electrochemical measurements further reveal that\nboth NFC-PTFE and NFC-NH F exhibit significantly reduced ring currents compared to NFC,\n4\naccompanied by lower H O selectivity and higher electron transfer numbers (Figure R1c–d).\n2 2\nThese results unambiguously demonstrate that excessive F-induced defect passivation suppresses\nthe 2e⁻ ORR pathway and shifts the reaction toward the 4e⁻ ORR process.\nIn summary, PVDF uniquely enables a balanced F incorporation, thereby achieving optimal\ndefect passivation for high 2e⁻ ORR performance. In contrast, PTFE and NH F introduce F in an\n4\noverly aggressive and uncontrollable manner, leading to excessive defect elimination and inferior\nR-3\ncatalytic performance. This comparison highlights that the selection of F sources is critical to the\ndefect passivation effect and catalytic performance.\nFigure R1. (a) Raman spectra of NFC-(NH F) and NFC-(PTFE). (b) Comparison of the I /I\nvalues. (c) LSV curves of NFC-(NH F) and NFC-(PTFE); The rotation is 1600 rpm, data was\n4\ncollected in the O -saturated 0.1 M KOH. (d) Calculated H O selectivity and electron transfer\n2 2 2\nnumbers.\n3. The DFT calculations indicate that F preferentially attacks and removes unstable pyrrolic and\npyridinic N species. Does this imply that the primary role of F is confined to \"defect passivation\"\nor the newly formed C-F/N-F sites as another active centers?\nResponse: We appreciate this very insightful comment, which allows us to clarify the exact nature\nof the active centers in this unique catalyst system.\nThe DFT results indicate that F preferentially interacts with and removes unstable nitrogen-\nrelated defect motifs (such as pyrrolic and pyridinic N), leading to the formation of new C–F and\nN–F configurations. These newly formed C–F/N–F motifs are described as “defect passivation” in\nthis work because they terminate unstable defect states and regulate the local electronic structure.\nImportantly, the formation of C–F/N–F motifs does not imply that F or N atoms themselves serve\nas the direct catalytic active centers. Rather, these motifs define a new active microenvironment,\nin which the carbon atoms close to or coordinated with F and N act as the true active centers.\nR-4\nTherefore, F plays a dual role: it passivates unstable defects while simultaneously generating\nnew C–F/N–F coordination environments that activate catalytically related carbon atoms for\nthe 2e⁻ ORR.\n4. In another paper (10.1038/s41467-023-40118-y) introduces a high-proportion pyrrole nitrogen-\ndoped graphene mesoporous carbon composite material for improving the performance of H O .\n2 2\nHowever, in Figure 4j of this manuscript demonstrates a positive correlation between H O\n2 2\nselectivity and graphitic N content, alongside a negative correlation with pyrrolic and pyridinic N.\nThis conclusion appears to be in direct contrast with findings reported in other established\nliterature.\nResponse: We thank the reviewer for raising this important point, which helps us clarify the\nmechanistic interpretation.\nThe referenced work (Nat. Commun. 2023, 14, 4430/10.1038/s41467-023-40118-y) reports\nenhanced 2e⁻ ORR performance on high-density dual pyrrolic-N sites (denoted as Dual-PyrN-Gr);\nhowever, a single pyrrolic-N site model was computationally evaluated in our manuscript. The two\nstudies operate under fundamentally different structural regimes, which lead to distinct activity–\nstructure correlations. For clarification, we added this reference as ref[11] in the revised manuscript.\n(a) The prior work evaluates a system intentionally enriched with adjacent dual pyrrolic-N.\nTheir DFT analysis shows that only dual-pyrrolic-N (rather than isolated pyrrolic-N) provides the\nnear-optimal ΔG . This configuration relies on a synergistic dual-site ensemble requiring a high\nOOH*\nlocal pyrrolic-N density. However, such a dual-pyrrolic-N site was not claimed in our manuscript.\nConsistent with our DFT screening (Figure 1f–h in our manuscript), pyrrolic-N is isolated, defect-\nadjacent, electronically unstable, and is preferentially removed during the F-induced De-N–F\ncascade. Thus, isolated pyrrolic-N acts as a non-selective or unstable adsorption site, leading to its\nnegative correlation with H O selectivity in Figure 4j, which is also in line with the DFT\n2 2\ncalculations.\n(b) Mechanistic frameworks differ: dual-site kinetic enhancement vs. defect-passivation\nelectronic tuning. The work (10.1038/s41467-023-40118-y) focuses on dual-pyrrolic ensembles to\nlower the kinetic barrier for the 2e⁻ pathway. Our work focuses on F-induced defect passivation\nR-5\nand charge redistribution, which suppresses unstable N species and shifts activity toward\nelectronically tuned (N, F)-codoped sites. Therefore, the governing mechanisms are inherently\ndistinct.\n5. To consider practical viability, some post-catalytic characterization of the catalyst should be\nperformed after Stability test. For example, XPS, the content of F and N, SEM?\nResponse: We appreciate this great suggestion. As the reviewer suggested, we performed the XPS\nand SEM for the NFC sample after the stability test.\nAs shown in Figure R2a, the atomic percentage of N in NFC (NFC catalyst after the\nafter\ndurability test is denoted as NFC ) is 1.13 at.%, which is essentially unchanged compared with\nafter\nthat of fresh NFC (1.18 at.%). Furthermore, the N 1s spectra and corresponding deconvolution\n(Figure R2b-c) reveal that the overall N chemical states remain comparable before and after\nstability testing, manifesting the chemical stability of the carbon framework under long-term\nstability testing. Notably, we noted that the electrode was prepared using a Nafion binder, which\ncontains covalent C–F bonds and therefore contributes to the background F signal. As a result,\npost-stability F 1s XPS cannot be used as a quantitative indicator for tracking the intrinsic F\ndopants in NFC. Additional SEM was performed on NFC , which shows the uniform elemental\nafter\ndistribution. Furthermore, as shown in Figure R2e-f, HRTEM of NFC still exhibits clear carbon\nafter\nfringes without noticeable structural collapse or severe amorphization, manifesting that the\nstructure was well preserved after the stability test.\nWe also added the related discussion and more data (Figure S40) to the revised manuscript\n(Pages 17-18) and Supplementary Materials, respectively, to clarify the structural stability after\nelectrochemical tests:\nTo consider practical viability and directly validate the retention of F-induced defect\npassivation, post-catalytic characterizations of the NFC were performed after stability tests. As\nshown in Figure S40a, the atomic percentage of N in NFC after the durability test (denoted as\nNFC ) is 1.13 at.%, which is essentially unchanged compared with that of fresh NFC (1.18 at.%).\nafter\nMoreover, the N 1s spectra and corresponding peak deconvolution (Figure S40b–c) reveal that\nthe overall distribution of N chemical states remains comparable before and after long-term\nR-6\noperation, indicating the chemical stability of the carbon framework. Additional SEM and STEM-\nEDX characterization of NFC confirms a uniform elemental distribution (Figure S40d and\nafter\nFigure S41b). Furthermore, HRTEM images (Figure S40e–f) show well-defined carbon fringes\nwithout noticeable structural collapse or severe amorphization, demonstrating that the carbon\nframework is well preserved after the stability tests. Consistently, Raman spectra show that\nNFC maintains an essentially unchanged defect signature, with I /I = 0.951 (Figure S41b),\nafter D G\nvery close to that of pristine NFC (I /I ≈ 0.95), indicating that the overall defect/graphitic\nD G\nbalance is retained after long-term operation.\nR-7\nFigure R2. (a) The XPS survey and atomic percentage of NFC after stability test. (b) High-\nresolution XPS N 1s spectrum. (c) Relative N species of NFC and NFC . (d) EDX and SEM. (e-\nafter\nf) TEM images of NFC .\nafter\n6. After the electrolyser has been in use for 105 hours. Was there any specific drop of yield after\nthat?\nResponse: We thank the reviewer for this great comment. In the electrolyzer tests, we typically\ntake three measurements for each data point to minimize the impact of data fluctuations (see\nFigure R3). As shown in Figure R3 and the data summarized in Table R1, the electrolyzer\nmaintains a high and relatively stable H O yield (typically >90%) throughout the entire\n2 2\ncontinuous tests beyond 100 hours. Although the production output showed greater fluctuations\nand a larger margin of error after approximately 105 hours, the stability remained within a\nreasonable range. Importantly, we did not observe a monotonic decay trend, suggesting that the\ncatalyst remained essentially active and that mass transfer or interfacial factors likely contributed\nto the observed fluctuations under prolonged high-current operating conditions. Therefore, we only\npresent data up to approximately 105 hours.\nFigure R3. Average Faraday efficiency (or yield) with error bars within stability test at a current\ndensity of 300 mA cm-2.\nR-8\nTable R1. Yield after 108 hours of test.\nTime (h) Yield (%)-1 Yield (%)-2 Yield (%)-3 Average Yield (%)\n104.51 97.67 92.94 95.93 95.51\n106.31 84.5 87.08 86.63 86.07\n107.31 86.85 86.72 81.47 85.01\n108 93.03 82.32 89.86 88.4\nTo Reviewer #2:\nIn this study, the authors aimed to systematically design and screen active sites on N-doped carbons\nusing F-doping, supported by statistical analysis, DFT calculations, and operando experiments.\nThey found that fluorine-induced defect passivation optimizes OOH* binding and enables N,F co-\ndoped carbon to achieve nearly 100% H₂O₂ selectivity, high current densities, and long-term stable\nH₂O₂ production in an electrolyzer. Coupling the 2e⁻ ORR with methanol oxidation further reduces\nthe cell voltage and greatly improves productivity, demonstrating a practical and economically\nfavorable route for scalable H₂O₂ electrosynthesis. Here, I mainly evaluate the theoretical\ncalculation aspects of this manuscript. I did not identify major issues in their calculations, and the\nresults and discussion appear scientifically sound. However, there are several points that require\nclarification, as listed below.\nResponse: We are grateful to the reviewer for the very positive feedback on our work. We have\ncarefully considered and incorporated the valuable suggestions, and we hope that the revised\nmanuscript will be suitable for publication.\n1. In lines 120-121, the authors state that \"A physical filter based on the adsorption distance\n(dOOH*) of OOH* intermediate (d >2 Å, Figure 1c) was ...\" It is unclear how the threshold of 2\nÅ was determined.\nResponse: We thank the reviewer for pointing out the need to clarify the selection of the distance\nthreshold. In the revised Supplementary Materials, we added a quantitative justification based on\nR-9\nour complete dataset of 66 optimized OOH* adsorption configurations on N/F-doped\nconfigurations.\nIn Table S3 in the revised Supplementary Materials, we report the shortest distance between\nthe O atom of the OOH* intermediate and the nearest surface C atom for each adsorption site (last\ncolumn). A clear bimodal distribution is observed in Figure R4a-b. For chemisorbed OOH*,\nthe\nC–O bond length consistently falls in the range of 1.4–1.6 Å, which is characteristic of a covalent\nC–O bond on graphene-based configurations. This range is fully consistent with previous DFT\nstudies[1,2], where C–O bond lengths of ~1.5 Å are reported for chemically bonded configurations.\nIn contrast, for physisorbed OOH*, the shortest O–C distance lies between 2.72 and 3.84 Å,\nindicating weak, non-bonded interactions. Importantly, none of the 66 adsorption structures exhibit\nan intermediate C–O distance between 1.6 and 2.7 Å, revealing a clear geometric separation\nbetween bonded and non-bonded adsorption states. This bimodal distribution provides a\nquantitative, system-specific basis for distinguishing chemisorbed versus physisorbed OOH*\nconfigurations.\nBased on both our statistical analysis and established literature values for C–O bonding on\ngraphene-based configurations, we therefore selected 2.0 Å as a physically meaningful upper limit\nto identify a chemisorbed, covalently bonded OOH* configuration. We rewrote the sentence in\nTable S3 as “d(O–C)min is defined as the minimum distance between the O atom in OOH closest\nto the surface and the nearest surface C atom. Bonded configurations show d(C–O) ≈ 1.40–\n1.60 Å, whereas non-bonded ones exhibit d(O–C)min ≈ 2.72–3.84 Å.”\nR-10\nFigure R4 (a) Summary of the shortest distance between the O atom of the OOH* intermediate\nand the nearest surface C atom for each adsorption site. (b) Distribution of bond length of the 66\nconfigurations.\nReference\n[1] Wang, jinlong, et al. “Dft Study of the Catalytic Activity for Oxygen Reduction Reaction in\nMulti-N-Doped Graphene.” SSRN Electronic Journal, 1 Jan. 2024.\n[2] Chiara Ricca, Frederic Labat, Nino Russo, Carlo Adamo, and Emilia Sicilia. Oxidation of\nethylbenzene to acetophenone with n-doped graphene: insight from theory. The Journal of Physical\nChemistry C, 118(23):12275–12284, 2014.\n2. The authors should check the validity of the sentence \"While the formation energies for F\nattacking pyridinic-N (F-A-Pyri-N) and pyrrolic-N (F-A-Pyrr-N) are 2.71 eV and 0.18 eV (or –\n1.45 eV), respectively,...\" in lines 197-199, because the content appears to be inconsistent with Fig.\n2c.\nResponse: We thank the reviewer for pointing out this inconsistency, and apologize for the\nmisleading description in our manuscript. The original text did not clearly distinguish the two\nstructural models used for evaluating the pyrrolic-N configurations, which was confusing when\ncompared with Figure 2c. We revised the sentence in lines 197–199 of the original manuscript to\nensure that the numerical values and their corresponding structural contexts are accurately\ndescribed and fully consistent with Figure 2c. Please see below (Page 11 in the revised manuscript):\nWhile the formation energies for F attacking two pyridinic-N sites (F-A-Pyri-N-1, or F-A-\nPyri-N-2) and one pyrrolic-N site (F-A-Pyrr-N) are 2.71 eV, 0.18 eV, and -1.45 eV, respectively,\nindicating that pyrrolic-N sites are considerably more susceptible to F compared to pyridinic-N.\nWe sincerely thank the reviewer for helping us to improve the quality of our manuscript.\n3. Also, the expression \"The optimized performance of NFC (Figure 4a) highlights\" in lines 277-\n278 may not be correct. It is unclear to me which figure the authors intended to cite.\nR-11\nResponse: We thank the reviewer’s great suggestion and apologize sincerely for the misleading\ndescription in our manuscript. In the cited literature (ACS Energy Lett. 9, 1331-1338, (2024)), in\nthe “Abstract section”, the author claimed that “Density functional theory calculations associate\nthe enhancement with stabilization of the *OOH key intermediate as a result of locally induced\nfield effects from the AMCs.”, so we have a discussion of “The optimized performance of NFC\n(Figure 4a) highlights” in lines 277-278. To avoid any potential misinterpretation, we deleted the\ncited reference 31 and the discussion of “This field channels electrons toward the low-Φ domains,\nstabilizing the OOH* intermediate”. As the performance of NCF is the best among all the samples\nin this manuscript, and NCF exhibits local in-plane built-in electric field and field-guided electron\nchanneling, therefore, we conclude that “The optimized performance of NFC (Figure 4a) reveals\nthis field-guided electron channeling is beneficial for 2e- ORR.” The removal of this sentence\ndoes not affect the original meaning or logic of the discussion, while avoiding potential\nmisinterpretation. We sincerely hope that the revised manuscript now meets the reviewer’s\nexpectations.\n4. The authors should clarify how the \"stability score\" shown in Fig. 4i is defined.\nResponse: We thank the reviewer for pointing out the need to clarify the definition of the stability\nscore. In this revised version, we have added a concise description of the procedure used to\ncompute the score in the Supplementary Materials (Section 2.4. Stability Analysis for Time-\nEnergy Trajectories for ab initio molecular dynamics (AIMD)).\nBriefly, we extracted the time-evolution of atomic positions from equilibrated AIMD\ntrajectories and analyzed their normalized (i) drifts, (ii) variabilities, and (iii) jitters. We combined\nthese quantities into a composite stability score between 0 and 100, where a higher score indicates\na higher structural stability. In addition, we provided a Python script (named “datatest”) to calculate\nthe “Stability Score” and confirm the repeatability. A detailed description was added to the\nSupplementary Materials. Please see below:\n2.4. Stability Analysis for Time-Energy Trajectories for ab initio molecular dynamics\n(AIMD)\nR-12\nWe evaluate time-energy stability using a range-normalized composite score that aggregates\ndrift, steady-state variability, and short-term jitter (DVJ score). The DVJ score was computed by\nAI, and the calculation process is attached below.\n2.4.1. Problem Setup and Notation\nLet the first column be the running time t (i = 1, …, N), and the subsequent column be the\ni\nenergy values y(m) for a selected configuration: m.\ni\nThe total time span T = t – t .\nN 1\nDefine the “production” (steady) window as the last half in time: H = {i|t ≥ t + 0.5T}.\ni 1\n2.4.2. Linear Drift (Trend)\nWe estimate linear trends by ordinary least squares (OLS).\nFull-record slope:\n∑𝑁 (𝑡 −𝑡̅)(𝑦 −𝑦̅)\n(Eq.1) 𝛽̂ = 𝑖=1 𝑖 𝑖 ,\nfull ∑𝑁 (𝑡 −𝑡̅)2\n𝑖=1 𝑖\nwhere 𝑡̅ and 𝑦̅ are the average values (means).\nLast-half slope:\n∑ (𝑡 −𝑡̅ )(𝑦 −𝑦̅ )\n(Eq.2) ̂𝛽 = 𝑖∈𝐻 𝑖 𝐻 𝑖 𝐻 .\nhalf ∑ (𝑡 −𝑡̅ )2\n𝑖∈𝐻 𝑖 𝐻\nFor readability, a scaled slope “per 1000 time-units : 𝛽̂ = 1000·𝛽̂.\nscaled\n1\n(Eq.3) 𝜇 = ∑ 𝑦 (mean),\n𝐻 |𝐻| 𝑖\n𝑖∈𝐻\n𝑖\n2.4.3. Steady-State Variability (Last-Half Statistics)\n1\n(Eq.4) 𝜎 = √ ∑ (𝑦 −𝜇 )2(population std),\n𝐻 |𝐻| 𝑖 𝐻\n𝑖∈𝐻\n(Eq.5) 𝑅 = 𝑚𝑎𝑥 𝑦 −𝑚𝑖𝑛 𝑦 (range),\n𝐻 𝑖 𝑖\n𝑖∈𝐻 𝑖∈𝐻\nR-13\nwith a small ε > 0 (e.g., 10−12) to avoid division by zero.\n2.4.4. Relative Drift (over the last half)\nNormalize the absolute drift over the last-half duration by the observed dynamic range:\n|𝛽̂ |(𝑡 −𝑡 )\nhalf 𝐻,𝑚𝑎𝑥 𝐻,𝑚𝑖𝑛\n(Eq.6) 𝐷 =\nrel 𝑅 +𝜀\n𝐻\nwhere 𝑡 and 𝑡 are the first/last times in 𝐻.\n𝐻,𝑚𝑖𝑛 𝐻,𝑚𝑎𝑥\n2.4.5. Short-Term Jitter (Normalized)\nDefine discrete derivatives and the median time step:\n𝑦 −𝑦\n𝑖+1 𝑖\n(Eq.7) 𝑑 = ,𝑖 = 1,…,𝑁−1;\n𝑖 𝑡 −𝑡\n𝑖+1 𝑖\n(Eq.8) Δ𝑡 = median(𝑡 −𝑡 ).\nmed 𝑖+1 𝑖\nMedian absolute derivative (MAD):\n(Eq.9) MAD = median(|𝑑 −median(𝑑 )|).\n𝑑 𝑖 𝑖\nNormalize by the rate required to traverse R over a typical step:\nH\nMAD\n𝑑\n(Eq.10) 𝐽 = .\nnorm 𝑅 /Δ𝑡 +𝜀\n𝐻 med\n2.4.6. Variability Relative to Range\n𝜎\n𝐻\n(Eq.11) 𝑉 = .\nrel 𝑅 +𝜀\n𝐻\n2.4.7. Composite Stability Score (0–100)\nCombine drift, variability, and jitter into a bounded score:\n100\n(Eq.12)𝑆 = .\n1+𝐷 +𝑉 +𝐽\nrel rel norm\nLarger S indicates higher stability.\nR-14\nTo clarify the calculation of the “Stability Score”, we provide a representative screenshot\nillustrating the computational procedure. As shown in Figure R5, taking the NF-HHP model as an\nexample, the time–energy data were used as input and processed using the datatest Python script.\nThe calculated stability score for NF-HHP is 82.67. The same procedure was consistently applied\nto all six models discussed in the manuscript. Notably, the datatest Python script was developed\nby explicitly implementing Eq. (1)–Eq. (12), and the complete source code is provided as the\n“datatest” to ensure full reproducibility.\nFigure R5 Demonstration of the stability score (“Score”) calculation workflow. The left panel\nshows the raw time–energy dataset used as input, while the right panel displays the execution of\nthe datatest Python script implementing Eq. (1)–Eq. (12).\nTo Reviewer #3:\nThe manuscript presents a comprehensive study integrating statistical learning, theoretical\ncalculation, materials synthesis, operando spectroscopy, and electrolyzer testing to investigate\nfluorine-induced defect passivation in nitrogen-doped carbons for selective 2e− ORR toward H O\n2 2\nR-15\nproduction. The work has potential significance for both mechanistic understanding and practical\nelectrosynthesis. However, despite the strengths, several aspects of the manuscript require\nsubstantial revision. Firstly, the central claim regarding “F-induced defect passivation as the\ndominant factor governing activity and stability” is not yet fully supported by the current set of\nevidence. The statistical-learning framework, although interesting, is complex and at times\ninsufficiently validated experimentally, which weakens the connection between theoretical\nscreening and real catalyst behavior. Secondly, several mechanistic interpretations, particularly\nthose related to Raman assignment of OOH* species, surface charge reversal, and the proposed\nbuilt-in electric field, need clearer justification and additional controls. Finally, the techno-\neconomic analysis relies heavily on assumptions that should be more explicitly stated, discussed,\nand critically assessed.\nOverall, the manuscript contains many promising elements, but the mechanistic claims, data\ninterpretation, and contextual analysis require deeper clarification and additional experimental or\nanalytical support. Addressing these issues will substantially enhance the scientific rigor and\npersuasiveness of the work. Therefore, this reviewer believes the work does not meet the high\nstandards of Nature Communications, particularly regarding material design and catalytic\nmechanism. This manuscript cannot be considered for publication in Nature Communications. The\ndetailed comments are as follows.\nResponse: We thank the reviewer’s positive feedback on our manuscript. We also appreciate the\nvaluable suggestions provided by the reviewers, which have greatly helped us to clarify our\nresearch findings and improve the quality of the manuscript. We have carefully considered all the\nsuggestions made and responded to each one individually. We sincerely hope that the reviewer will\nfind the revised manuscript suitable for publication in the revised version.\n1. The Introduction should be more concise and logically structured. Although the current\nbackground section contains substantial information, it does not sufficiently contextualize prior\nknowledge or clarify the remaining gaps. Numerous sites on carbon materials, including edge\ncarbons (Angew. Chem. Int. Ed. 2019, 58, 1100-1105; Adv. Funct. Mater. 2023, 33, 2305795),\nintrinsic defects (J. Am. Chem. Soc. 2023, 145, 21, 11589-11598; J. Phys. Chem. Lett. 2022, 13,\n8914-8920), and heteroatom-doped sites (Nat. Commun. 2021, 12, 4225; Adv. Energy Mater. 2024,\nR-16\n2304418; Nat. Commun. 2023, 14, 4430), have already been identified as potential active sites for\nthe 2e− ORR. These points should be incorporated into the discussion.\nResponse: We thank the reviewer for pointing out the necessity to incorporate the background\ndiscussion on the acknowledged active sites for 2e- ORR into the Introduction section, which\nsignificantly helps us to enhance the comprehensiveness of this manuscript. We added the\nfollowing discussion to the introduction section in the revised manuscript. In addition, we add the\nsignificant suggested publication as ref[11-17].\nThe newly added discussion is on Page 3 in the revised manuscript:\nOver the past decade, extensive efforts have identified a variety of active motifs in carbon-\nbased materials capable of promoting the 2e⁻ ORR. These include edge carbon atoms with\nunsaturated coordination,[1,2] intrinsic defect sites such as vacancies and topological distortions,[3,4]\nand heteroatom-doped configurations[5-7] that modulate local electronic structures. Such sites can\ngenerate localized charge or spin densities favorable for OOH* adsorption, enabling selective\nH O formation. Despite these advances, a fundamental challenge persists in metal-free carbon\n2 2\ncatalysts: the poor controllability of defect states. Especially, the heteroatom-doped carbon\ncatalysts exhibit significant atomic heterogeneity due to diverse dopant motifs and random defects,\nmaking it challenging to correlate structure with catalytic performance.\nReference\n[1] Sa, Y. J.; Kim, J. H.; Joo, S. H., Active Edge-Site-Rich Carbon Nanocatalysts with Enhanced\nElectron Transfer for Efficient Electrochemical Hydrogen Peroxide Production. Angew. Chem. Int.\nEd. 2019, 58 (4), 1100-1105.\n[2] Jing, L.; Tian, Q.; Li, X.; Sun, J.; Wang, W.; Yang, H.; Chai, X.; Hu, Q.; He, C., Dual-\nEngineering of Porous Structure and Carbon Edge Enables Highly Selective H2O2\nElectrosynthesis. Adv. Funct. Mater. 2023, 33 (47), 2305795.\n[3] Zhang, C.; Shen, W.; Guo, K.; Xiong, M.; Zhang, J.; Lu, X., A Pentagonal Defect-Rich Metal-\nFree Carbon Electrocatalyst for Boosting Acidic O2 Reduction to H2O2 Production. J. Am. Chem.\nSoc. 2023, 145 (21), 11589-11598.\n[4] Wang, W.; Zheng, Y.; Hu, Y.; Liu, Y.; Chen, S., Intrinsic Carbon Defects for the Electrosynthesis\nof H2O2. J. Phys. Chem. Lett. 2022, 13 (38), 8914-8920.\nR-17\n[5] Xia, Y.; Zhao, X.; Xia, C.; Wu, Z.-Y.; Zhu, P.; Kim, J. Y.; Bai, X.; Gao, G.; Hu, Y.; Zhong, J.;\nLiu, Y.; Wang, H., Highly active and selective oxygen reduction to H2O2 on boron-doped carbon\nfor high production rates. Nat. Commun. 2021, 12 (1), 4225.\n[6] Jing, L.; Tian, Q.; Wang, W.; Li, X.; Hu, Q.; Yang, H.; He, C., Unveiling Favorable\nMicroenvironment on Porous Doped Carbon Nanosheets for Superior H2O2 Electrosynthesis in\nNeutral Media. Adv. Energy Mater. 2024, 14 (19), 2304418.\n[7] Peng, W.; Liu, J.; Liu, X.; Wang, L.; Yin, L.; Tan, H.; Hou, F.; Liang, J., Facilitating two-\nelectron oxygen reduction with pyrrolic nitrogen sites for electrochemical hydrogen peroxide\nproduction. Nat. Commun. 2023, 14 (1), 4430.\nIn addition, the use of F-doped carbon in the 2e− ORR is not new (Angew. Chem. Int. Ed. 2025,\n64, e202503626; Adv. Mater. 2023, 35, 2208533). Given this situation, I recommend that the\nauthors reorganize and strengthen the introduction to better articulate the novelty of this work. The\ndiscussion should clearly progress from the challenge of poorly controlled defect states in metal-\nfree carbon, to the rationale behind fluorine-induced defect passivation, and finally to how this\nstudy addresses unresolved mechanistic questions and fills the existing knowledge gap.\nResponse: We thank the reviewer for the constructive and insightful comment. We agree that the\noriginal introduction, while information-rich, did not sufficiently articulate the logical progression\nof prior knowledge, existing gaps, and the specific novelty of this work. According to the\nreviewer’s suggestion, we have substantially reorganized and streamlined the introduction to\nimprove the clarity, coherence, and contextual depth. We also added the suggested publication in\nthe revised manuscript as ref[22-23]. As suggested by the reviewer, we further added a detailed\ndiscussion about F to the introduction section on Pages 4-5 in the revised manuscript. Please see\nbelow:\nAs the most electronegative element, F forms multi-bonding states and exhibits pronounced\nelectron-withdrawing capability, suggesting its potential to terminate unstable dangling bonds and\nredistribute local charge density. Although F doping shows some potential as a conventional\nelectronic dopant in 2e⁻ ORR catalysts,[8,9] its interaction with pre-existing defect motifs,\nparticularly N-related defects, has not been thoroughly studied, leading to a significant knowledge\nR-18\ngap in the design of metal-free catalysts. Particularly, several unresolved mechanistic questions\nremain: How does F interact with different nitrogen configurations and defect states? Can F-\ninduced defect passivation be translated into predictable regulation of OOH* adsorption? And how\ndoes such passivation simultaneously impact selectivity and long-term durability? Addressing\nthese questions is essential for establishing a unified structure–activity framework for F-modified\ncarbon catalysts.\nReference\n[8] Zhu, G.; Zhao, S.; Yu, Y.; Fan, X.; Liu, K.; Quan, X.; Liu, Y., Tuning Local Proton\nConcentration and *OOH Intermediate Generation for Efficient Acidic H2O2 Electrosynthesis at\nAmpere-Level Current Density. Angew. Chem. Int. Ed. 2025, 64 (28), e202503626.\n[9] Xiang, F.; Zhao, X.; Yang, J.; Li, N.; Gong, W.; Liu, Y.; Burguete-Lopez, A.; Li, Y.; Niu, X.;\nFratalocchi, A., Enhanced Selectivity in the Electroproduction of H2O2 via F/S Dual-Doping in\nMetal-Free Nanofibers. Adv. Mater. 2023, 35 (7), 2208533.\nWe have also included a chart below to illustrate the efforts made in each section of the\nintroduction to clarify the progress “from the challenge of poorly controlled defect states in metal-\nfree carbon, to the rationale behind fluorine-induced defect passivation, and finally to how this\nstudy addresses unresolved mechanistic questions and fills the existing knowledge gap.” We hope\nthat the introduction now effectively showcases the novelty and core knowledge discussed in this\nmanuscript.\nR-19\nR-20\n2. The statistical-learning section would benefit from clearer summarization. Figure 1 contains\nmany descriptors and correlation analyses. A more intuitive explanatory paragraph in the main text\nwould help readers grasp the key structure–activity insights without frequent consultation of\nsupplementary tables.\nResponse: We thank the reviewer for this great suggestion. We fully agree that Figure 1b contains\na rich set of descriptors and that a more explicit, intuitive guide would help readers quickly extract\nthe key structure–activity relationships without repeatedly consulting Supplementary Tables. To\naddress this point, we inserted a more intuitive explanatory paragraph in the main text.\nA clearer summarization on Page 9 in the revised manuscript was added as follows:\nIn essence, the statistical-learning analysis is used to extract key structure–activity insights\nfrom a highly heterogeneous set of active sites. Rather than focusing on individual configurations\nor isolated descriptors, this method identifies the types of local atomic features (e.g., F-substitution\nat N-sites and (N, F)-codoping-sites) consistently reduce abs(∆G ) across the 10 descriptors,\nOOH*\nrevealing that the F-induced defect passivation primarily governs the activity and selectivity in the\n2e⁻ ORR.\nA more intuitive explanatory paragraph was added to Pages 6-7 in the revised manuscript as\nfollows:\nFor better clarification, the statistical-learning analysis is built upon 10 local structural and\nelectronic descriptors that collectively capture the chemical environment of catalytic carbon sites.\nThese descriptors can be conceptually grouped into three categories: (i) local coordination and\ngeometry, including the coordination number (CN), ring type (R-T), and average C-C bond length\naround the catalytic carbon site (ave. C-C), which describe defect topology and local lattice\ndistortion; (ii) compositional proximity descriptors, including C-neigh, N-neigh (N-N), F-neigh\n(F-N), as well as the numbers of N and F atoms in the configuration, which quantify the chemical\nneighborhood of the active carbon; and (iii) adsorption-related and electronic descriptors, namely\nthe distance between OOH* and catalytic active site (d) and the net charge on the active carbon\n(N-cha), which directly reflect adsorption condition and local electronic polarization. Collectively,\nthese 10 descriptors provide a framework to correlate defect structure, heteroatoms doping,\nelectronic modulation, and OOH* adsorption behavior across diverse active sites.\nR-21\n3. The discussion of F attacking different N species could be expanded. Figure 2c suggests that\npyrrolic-N is most vulnerable, yet the experimental validation is relatively brief. Additional\nspectral evidence (e.g., fitting residuals of N 1s or differential N K-edge spectra) would strengthen\nthe conclusion.\nResponse: We thank the reviewer for this great suggestion. We agree that the discussion of F\nattacking different N species should be strengthened. To address this, we have expanded the\ndiscussion in the revised manuscript to clarify the chemical fundamentals and the experimental\nevidence. Additional spectral evidence and discussion were also added to the revised manuscript\nto strengthen this conclusion. In addition, we also added Figure R6 and Figure R7 into the revised\nmanuscript as Figure S21 and Figure S24, respectively. Please see the following content added to\nthe revised manuscript (Pages 11-12):\nDFT calculations of the formation energy of different N- or F-containing configurations were\nperformed to further understand the De-nitrogenation–fluorination process (Figure 2c). Notably,\nthe formation energy for F attacking graphite-N (F-A-Gra-N) is as high as 5.68 eV. While the\nformation energies for F attacking two pyridinic-N sites (F-A-Pyri-N-1, or F-A-Pyri-N-2) and one\npyrrolic-N site (F-A-Pyrr-N) are 2.71 eV, 0.18 eV, and –1.45 eV, respectively, indicating that\npyrrolic-N sites are considerably more susceptible to F compared to pyridinic-N. This result\nindicates that three N-species follow the stability order: graphite-N > pyridinic-N > pyrrolic-N.\nThe stability order can be explained as follows. Pyridinic-N is incorporated in a six-membered\nring and well matched to the graphene lattice; its lone pair occupies an sp2 orbital in the ring plane\nand does not contribute to the π system, enabling a rigid sp2 framework with stronger C–N bonding.\nBy contrast, pyrrolic-N resides in a five-membered ring that imposes intrinsic topological strain;\nits lone-pair electrons participate in the π-conjugated system, which redistributes electron density,\nweakens the σ C–N bonds, and creates a chemically vulnerable, electron-rich defect motif. As a\nresult, pyrrolic-N is energetically more prone to being attacked and reconstruction, making it the\nmost susceptible N species during F-induced defect passivation, while pyridinic-N and especially\ngraphitic-N embedded in a more rigid sp² network are comparatively stable.\nFurther experimental characterizations, including X-ray Photoelectron Spectroscopy (XPS)\nand X-ray Absorption Near-Edge Structure (XANES), were performed to confirm the stability\norder of the three N species during the De-nitrogenation–fluorination process. The fitting residuals\nR-22\nof the N 1s XPS spectra were plotted. As shown in Figure S21, the residual plots of NFC, NC, and\nNFC are narrowly distributed around zero across the pyrrolic-N, pyridinic- and graphitic-N\ncontrol\nregions, confirming that the well-adapted XPS deconvolution. The relative content of graphite-N\ngradually increases, while the pyridinic-N and pyrrolic-N decrease (Figure 2d and Figure S22),\nconfirming that graphitic-N sites are least affected. Further absolute content of N species shows\nthe reduced content of N species after F attacking, following the order of graphite-N < pyridinic-\nN < pyrrolic-N (Figure 2e and Figure S23), which indicates that pyrrolic-N exhibits the largest\nloss, followed by pyridinic-N, with minimal removal of graphitic-N, consistent with the DFT-\npredicted stability order. Furthermore, as shown in Figure S24, the differential N K-edge spectra\nreveal a pronounced attenuation of pyrrolic-N after enhanced fluorination (NFC vs. NFC ),\ncontrol\nwhereas the changes in pyridinic-N are much weaker and the graphitic-N region remains largely\nintact. This directly confirms that F preferentially perturbs unstable pyrrolic-N rather than\nuniformly removing all N species, and also reveals the preferential vulnerability of graphite-N <\npyridinic-N < pyrrolic-N (corresponding stability order: graphite-N > pyridinic-N > pyrrolic-N).\nThese results demonstrate that the De-N–F cascade arises from F preferentially attacking pyrrolic-\nand pyridinic-N, leading to N removal and simultaneous F incorporation into the carbon lattice.\nMoreover, both pyridinic- and pyrrolic-N peaks in NFC exhibit positive binding energy shifts of\n~0.2 eV and ~0.1 eV, respectively (Figure 2d), indicating the electron density depletion at N-sites\ncaused by the strong electron-withdrawing nature of F-dopants.\nR-23\nFigure R6. Fitting residuals of N 1s.\nR-24\nFigure R7. Differential N K-edge spectra. Δ(TEY) = NFC(TEY) − NC(TET) or Δ(TEY) =\nNFC (TEY) − NC(TET). Data comes from Figure 3e.\ncontrol\n4. The peak assignments in the Raman spectra require support from appropriate literature or\nreference databases. In addition, previous studies indicate that an adsorbed O species typically\n2\nexhibits a characteristic band within the range of 1000 to 1200 cm-1 (Nano Lett. 2024, 24, 1650-\n1659; Adv. Mater. 2025, 2415712; Nat. Commun. 2024, 15, 983). Therefore, it is not appropriate\nto attribute all features in this region solely to the OOH* intermediate.\nResponse: We thank the reviewer for pointing out this inconsistency, and truly apologize for our\ncarelessness. We agree that adsorbed O species (O *) typically exhibit Raman features in the\n2 2\n1000–1200 cm⁻¹ region and that it is inappropriate to attribute all signals in this range solely to\nOOH*. Accordingly, we have revised the peak assignments and updated the operando Raman\nanalysis. As shown in the revised Figure R8, features in the 1000–1200 cm⁻¹ region are now\nR-25\nassigned to O *. We solidly support the reviewer’s suggestion and cited the recommended\n2\nliterature as Ref[42-44]. We also revised the main text on page 20 in the revised manuscript as\nfollows:\n“as the applied potential decreases below 0.7 V vs. RHE, weak but detectable features emerge\naround 1000⁓1200 cm-1 and 1530 cm-1, which are attributed to vibrational modes associated with\nadsorbed O species (O *), and surface-bound OOH* species, respectively (Figure 5b).”\n2 2\nFigure R8 (a) Schematic of the operando Raman cell used to monitor surface intermediates during\nORR. (b) In-situ Raman spectra and (c) corresponding spectral variations at different potentials.\n5. The zeta-potential discussion should distinguish global surface charge from local electronic\nmodulation. The observed shift from positive to negative charge is described qualitatively.\nIncorporating DOS or Bader charge comparison between NC and NFC would more rigorously\nsupport the claim of charge-state reversal and its influence on selectivity.\nResponse: We appreciate the reviewer’s suggestion to provide local electronic evidence in addition\nto the global zeta-potential data. We fully agree that zeta-potential reflects the global surface charge,\nwhereas catalytic selectivity is typically governed by local electronic structure at the active sites.\nAs recommended, the Bader charge analysis was employed to analyze the charge-state reversal\nand its influence on selectivity as follows (new Table S8, Table R2 in the response letter). We also\nadded this discussion to Page 15 in the revised manuscript.\nR-26\nIn addition, we also analyzed the local electronic modulation using the Bader charge (Table\nS8). Regarding N-doped configurations, the Bader analysis reveals pronounced charge\npolarization: N atoms carry substantial negative charge (−0.95 to −1.29 e), while the catalytically\nrelevant carbon atoms exhibit strong positive charges (+0.327 to +0.676 e), indicating highly\nelectron-deficient carbons. Upon F incorporation, F atoms consistently act as strong electron-\nwithdrawing centers (−0.627 to −0.680 e), which results in the positive charge reduction of the\ncatalytically relevant carbon atoms. For example, the Bader charge of those carbon atoms in the\nF-doped configurations (+ 0.278 to + 0.372 e) and (N, F)-codoped configurations (+0.297 to\n+0.495 e) are reduced compared to that of the N-doped configurations (+0.327 to +0.676 e).\nTherefore, F incorporation into NC provides microscopic evidence that the local electronic\nenvironment of different configurations is fundamentally altered, which regulates the OOH*\nadsorption and the reaction selectivity. In addition, the microscopic charge-state reversal can\nchange the surface adsorption species, thereby resulting in an apparent reversal of the global\nsurface charge measured by zeta potential.\nTable R2. Local Bader Charge Modulation in Pristine, N-Doped, F-Doped, and N, F-codoped\nconfigurations.\nName Top view\nGraphitic N\n(G-N)\nR-27\nPyridinic N\nsmall hole\n(Pyri-N-SH)\nPyridinic N\nlarge hole\n(Pyri-N-LH)\nPyridinic N\nhuge hole\n(Pyri-N-HH)\nPyrrolic N\nhuge hole\n(Pyrr-N-HH)\nR-28\nF-huge-hole\n(F-HH)\n2F-huge\nhole (2F-\nHH)\n3F-huge-\nhole (3F-\nHH)\nN-F-huge\nhole para\n(NF-HHP)\nR-29\nN-F-huge\nhole meta\n(NF-HHM)\nN-F-huge\nhole ortho\n(NF-HHO)\n6. Normalizing activity using ECSA (Figure 4e) requires clarification of its validity. The double-\nlayer capacitance of carbon materials does not necessarily correlate with the density of intrinsic\nactive sites, particularly because fluorine doping may change the hydrophilicity or hydrophobicity\nof the surface and thus alter the measured ECSA. A brief explanation of the rationale for using C\ndl\nas a proxy, along with its limitations, would improve the scientific rigor of the analysis.\nResponse: We thank the reviewer for pointing out this meaningful viewpoint regarding the validity\nand limitations of ECSA normalization. We fully agree that the double-layer capacitance (C )\nof\ndl\ncarbon materials does not strictly represent the absolute density of intrinsic catalytic sites,\nespecially when surface chemistry (e.g., fluorine doping) modifies wettability and interfacial\nproperties.\nIn this work, ECSA derived from C is not intended to quantify the exact number of intrinsic\ndl\n2e⁻ ORR active sites, but rather to provide a relative electrochemically accessible surface metric\nunder identical measurement conditions. Accordingly, ECSA-normalized activity is employed to\nhelp distinguish accessibility-related effects from intrinsic catalytic trends, rather than to infer\nabsolute active site counts. A brief clarification has been added to the revised manuscript in Figure\nR-30\n4e caption to justify the rationale for using C as an accessibility-related metric and to explicitly\ndl\nstate its limitations for heteroatom-doped carbon systems. Please see below:\nIt should be noted that the ECSA estimated from C mainly reflects the electrochemically\ndl\naccessible interfacial area rather than the absolute density of intrinsic active sites; therefore,\nECSA-normalized currents are used here only as a relative, supporting metric under identical\nmeasurement conditions.\n7. Post-stability structural characterizations are encouraged. After long-term operation (Figure 4g),\nXPS, Raman, or TEM analyses of the used NFC catalyst would directly validate the retention of\nF-induced defect passivation.\nResponse: We thank the reviewer for this valuable suggestion, which significantly helps us to\nimprove the quality of our manuscript. We agree that post-stability structural characterizations are\nimportant to directly verify the structural integrity and the retention of the F-induced defect-\npassivation after long-term operation. Based on the reviewer’s suggestion, we performed post-\ncharacterization, including XPS, Raman, and TEM, and added these results as Figure R5. We fully\ndiscussed the post characterizations from the following two aspects:\n(a) Elemental distribution and chemical stability\nAs shown in Figure R9a, STEM-EDX mapping indicates that the elements remain uniformly\ndistributed on the carbon nanoparticles after the long-term stability test, without observable\nsegregation. The atomic percentage of N in NFC (NFC catalyst after the durability test is\nafter\ndenoted as NFC ) is 1.13 at.% (Figure R9b), which is essentially unchanged compared to fresh\nafter\nNFC (1.18 at.%). Furthermore, the N 1s spectra and deconvolution (Figure R9c) show that the\noverall N chemical states remain comparable before and after stability testing, manifesting the\nchemical stability of the N-doped framework under long-term stability testing.\n(b) Structural integrity and defect-state retention\nTo further evaluate whether the carbon framework and defect-passivation-related structure\nare preserved after durability testing, we conducted HRTEM and Raman analyses. As shown in\nFigure R9d-e, NFC still exhibits clear carbon fringes without noticeable structural collapse or\nafter\nsevere amorphization. Consistently, Raman spectra show that NFC maintains an essentially\nafter\nunchanged defect signature, with I /I = 0.951, very close to that of pristine NFC (I /I ≈ 0.95)\nD G D G\n(Figure R9f), indicating that the overall defect/graphitic balance is retained after long-term\noperation.\nCollectively, these post-characterizations of NFC demonstrate that the NFC catalyst\nafter\nmaintains (i) stable elemental distribution and N chemical states, and (ii) preserved carbon\nframework/defect structure after durability testing.\nIn addition, we also added related discussion to the revised manuscript (Pages 17-18) for\ndirectly validating the retention of F-induced defect passivation. Please see the following.\nTo consider practical viability and directly validate the retention of F-induced defect\npassivation, post-catalytic characterizations of the NFC were performed after stability. As shown\nin Figure S40a, the atomic percentage of N in NFC after the durability test (denoted as NFC )\nafter\nis 1.13 at.%, which is essentially unchanged compared with that of fresh NFC (1.18 at.%).\nMoreover, the N 1s spectra and corresponding peak deconvolution (Figure S40b–c) reveal that\nthe overall distribution of N chemical states remains comparable before and after long-term\noperation, indicating the chemical stability of the carbon framework. Additional SEM and STEM-\nEDX characterization of NFC confirms a uniform elemental distribution (Figure S40d and\nafter\nFigure S41b). Furthermore, HRTEM images (Figure S40e–f) show well-defined carbon fringes\nwithout noticeable structural collapse or severe amorphization, demonstrating that the carbon\nframework is well preserved after the stability test. Consistently, Raman spectra show that NFC\nafter\nmaintains an essentially unchanged defect signature, with I /I = 0.951 (Figure S41b), very close\nD G\nto that of pristine NFC (I /I ≈ 0.95), indicating that the overall defect/graphitic balance is retained\nD G\nafter long-term operation.\nR-31\nR-32\nFigure R9. Post-stability characterization of NFC after long-term operation. (a) STEM image and\ncorresponding EDX elemental mappings of C, N, and F for NFC after the stability test (NFC ),\nafter\nshowing uniform elemental distribution. (b) XPS survey spectrum of NFC . (c) Comparison of\nafter\nN species distribution in fresh NFC and NFC . (d, e) TEM and HRTEM images of NFC . (f)\nafter after\nRaman spectrum of NFC .\nafter\nR-33\n8. Key techno-economic assumptions should be explicitly summarized in the main text. Although\ndetails are in the Supplementary Information, the economic analysis would be clearer if electricity\ncost, methanol price, and system-scale assumptions were briefly stated.\nResponse: We thank the reviewer for this constructive suggestion. To improve the clarity of the\ntechno-economic analysis, we have now summarized the key economic assumptions directly in\nthe main text on Page 23 in the revised manuscript. Please see below:\nTo evaluate system viability, a techno-economic analysis (TEA), based on the global average\nprice and reported work[10], was conducted based on an industrially relevant electrolyzer scale,\naccounting for key inputs and outputs including energy consumption ($0.05 kWh-1), methanol\n($0.67 kg-1), H O production ($1.087 kg-1), and K CO byproduct ($1.14 kg-1), and assumed\n2 2 2 3\nsystem scale (500 m2 electrolyzer area with industrially relevant capital and balance-of-plant costs).\n(see Supplementary Note 1 for detailed assumptions and cost breakdowns).\nReference\n[10] Sun, Y.; Fan, K.; Li, J.; Wang, L.; Yang, Y.; Li, Z.; Shao, M.; Duan, X., Boosting\nelectrochemical oxygen reduction to hydrogen peroxide coupled with organic oxidation. Nat.\nCommun. 2024, 15 (1), 6098.\n9. Based on the RRDE-derived LSV curves (Figure 4a) and the corresponding H O selectivity\n2 2\n(Figure 4c), the improvement gained from fluorine doping (NFC) appears minimal, and the\nenhancement over the NC sample is not clearly demonstrated. This weak correlation with the\nauthors' theoretical predictions reduces the overall persuasiveness of the work.\nResponse: We thank the reviewer for this great comment, which offers us the opportunity to clarify\nthe apparent discrepancy between the RRDE measurements and the theoretical predictions.\nThe RRDE-derived disk current density in Figure 4a reflects the overall oxygen reduction\nactivity. Regarding a catalyst that selectively favors the 2e⁻ ORR pathway, a reduction in the\ncompeting 4e⁻ ORR contribution is expected. Consistent with this expectation, Figure 4a shows\nthat F doping (or F passivation) leads to an increase in the H O -related ring current, and the H O\n2 2 2\ncurrent in Figure R10a (derived from Figure 4b) is significantly reduced, indicating a clear\nR-34\npathway shift from the 4e⁻ ORR toward the 2e⁻ ORR. This pathway transition after fluorine doping\nis more quantitatively captured by analyzing the H O current. As summarized in Figure R10b, F\n2\ndoping results in an approximately 85% reduction in the H O formation current, directly\n2\ndemonstrating the effective suppression of the 4e⁻ ORR pathway and the promotion of selective\nH O generation. Importantly, this performance enhancement is further supported by the improved\n2 2\ndurability of NFC compared with NC, highlighting the beneficial role of F-induced defect\npassivation in stabilizing the 2e⁻ ORR pathway. From a theoretical perspective, the DFT\ncalculations predict that F incorporation into N-based configurations significantly reduces\nabs(ΔG ) to a near-zero value (0.006 eV), which favors optimal OOH* stabilization and\nOOH*\nselectively promotes the 2e⁻ ORR. Therefore, the experimental RRDE results and the theoretical\npredictions are fully consistent in demonstrating that F doping regulates reaction selectivity by\nsuppressing the competing 4e⁻ ORR rather than by simply increasing the total ORR current.\nTherefore, although the enhancement in geometric disk current density appears modest, the\ncombined analysis of H O currents, stability, and theoretical energetics clearly establishes the\n2\ndecisive role of F doping in directing the ORR toward the 2e⁻ pathway. This discussion was added\nas “Discussion 4” in the revised Supplementary Materials. And Figure R10 was added to the\nrevised Supplementary Materials as Figure S36. Please see the following:\nThe RRDE-derived disk current density in Figure 4a reflects the overall oxygen reduction\nactivity. In fact, for a catalyst that selectively favors the 2e⁻ pathway, a reduction in the competing\n4e⁻ ORR contribution is expected. Consistent with this expectation, Figure 4a shows that F doping\nleads to an increase in the H O -related ring current. Importantly, the H O current in Figure S36a\n2 2 2\n(derived from Figure 4b) is significantly reduced, indicating a clear pathway shift from the 4e⁻\nORR toward the 2e⁻ ORR. This pathway transition is more quantitatively captured by analyzing\nthe H O current. As summarized in Figure S36b, F doping results in an approximately 85%\n2\nreduction in the H O formation current, directly demonstrating the effective suppression of the 4e⁻\n2 2\nenhancement is further supported by the improved durability of NFC compared with NC,\nhighlighting the beneficial role of F-induced defect passivation in stabilizing the 2e⁻ ORR pathway.\nFrom a theoretical perspective, the DFT calculations predict that F incorporation into N-based\nconfigurations significantly reduces abs(ΔG ) to a near-zero value (0.006 eV), which favors\nOOH*\noptimal OOH* stabilization and selectively promotes the 2e⁻ ORR. Therefore, the experimental\nRRDE results and the theoretical predictions are fully consistent in demonstrating that F doping\nregulates reaction selectivity by suppressing the competing 4e⁻ ORR rather than by simply\nincreasing the total ORR current.\nTo clearly clarify the effect of F on enhancing the 2e- ORR performance, we also added a\nrelated description to Page 16 in the revised manuscript. Please see the following screenshot:\nFigure R10. (a) RRDE-derived disk and H O partial current densities for NC and NFC. (b)\nsuppression of the 4e⁻ ORR pathway after fluorine doping.\nR-35\nSome minor comments:\nR-36\n1. Consistency of notation and symbols across figures should be improved. Some abbreviations\n(e.g., ORR//MOR vs ORR//OER) differ slightly in formatting across figures, and ΔGOOH*\nappears with inconsistent styling. Unifying these will improve clarity and professionalism.\nResponse: We thank the reviewer for pointing out the typographical errors. We have carefully\nreviewed the entire manuscript and corrected all identified typos accordingly.\n2. The conclusion could more clearly highlight the methodological contribution. Beyond material\ndevelopment, the combined use of statistical learning, DFT calculations, operando spectroscopy,\nand flow-cell validation forms an integrated framework that can be applied to other catalytic\nsystems. Explicitly emphasizing this transferable aspect would strengthen the overall impact of the\nwork.\nResponse: We thank the reviewer for this insightful suggestion, which significantly helps us to\nimprove the quality of the Discussion Section. We agree that, beyond the development of a specific\ncatalyst system, an important contribution of this work lies in the integrated methodological\nframework that combines statistical learning, DFT calculations, operando spectroscopy, and flow-\ncell validation. In response to this comment, we explicitly emphasized this transferable aspect and\nadded the following discussion to the Discussion Section on Page 26 in the revised manuscript.\nPlease see the following text:\nIn summary, this work conceptualizes a transferable framework for rational catalyst design.\nBeyond advancing commercial H O production, the crucial contribution is a closed-loop\n2 2\nworkflow that can be readily ported to other electrocatalytic systems with complex defect\nchemistry and pathway selectivity. Specifically, the framework consists of five modular steps: (i)\nConstructing reasonable local motifs/active-site candidates based on the experimental or\ntheoretical data; (ii) enumerating realistic motifs/sites and encoding them with physically\ninterpretable descriptors; (iii) performing DFT calculations to translate these descriptor trends into\nmechanistic, energetics-based design rules; (iv) using statistical or machine learning to identify the\ndominant descriptors to prioritize high-value structures; (v) experimentally validating both the\npredicted structure–activity logic, followed by device-level testing.\nR-37\nImportantly, while the specific intermediate (OOH*) and performance target (2e⁻ ORR) are\nunique to H O electrosynthesis, the transferable elements are the methodology and decision logic:\n2 2\nthe descriptor-guided screening of active sites, and the theory–experiment cross-validation. When\nextended to reactions such as CO reduction or nitrogen fixation, the same workflow can be\n2\nimplemented by substituting the reaction-defining intermediates and descriptors (e.g.,\n*COOH/*CO for CO RR or *N H/*NH for N RR). Therefore, this paradigm provides a\n2 2 x 2\ngeneralizable roadmap for coupling electronic-structure engineering with half-reaction synergy to\naccelerate the discovery, mechanistic understanding, and scale-up validation of sustainable\nelectrocatalytic processes.\nTo Reviewer #4:\nThis manuscript, entitled “From Active-Site Design to Electrolyzer Innovation: F-Modified Metal-\nFree Catalysts Drive H O Electrosynthesis at Industrial-Scale Current Density,” presents an\n2 2\ninnovative approach by employing statistical learning to screen active sites for the two-electron\noxygen reduction reaction. The proposed regulatory mechanism is substantiated through\nexperimental characterization, in situ spectroscopy, and theoretical calculations. The optimized\ncatalyst exhibits outstanding catalytic activity and stability in a three-electrode flow cell, achieving\nstate-of-the-art performance. However, revisions are needed before the manuscript can be\nconsidered suitable for publication in Nature Communications.\nResponse: We appreciate the reviewer’s very positive comments on our manuscript and for the\nstrong support for the publication of this work. To further improve the quality of this manuscript,\nwe reply to the comments point by point based on the reviewer’s meaningful comments.\n1. While the study focuses on the effects of nitrogen and fluorine doping in carbon-based catalysts,\nFigure S19 reveals a significant oxygen content in the samples. Given that oxygen-doped carbon\nmaterials are well-established as effective 2e⁻–ORR catalysts—with numerous studies\ndemonstrating their high activity in alkaline media—and Supplementary Figure S33 shows that\nBlank-C (containing only oxygen dopants) displays activity and selectivity comparable to the NFC\nR-38\nsample, it is essential to include control experiments that conclusively rule out the contribution of\noxygen to the catalytic performance.\nResponse: We thank the reviewer for this important comment. Oxygen functional groups are\nknown to contribute to 2e⁻ ORR in carbon-based materials. While in this work, the data in the\noriginal Supplementary Figure S33 clearly demonstrate that O-doping alone cannot achieve the\nhigh activity and selectivity compared with the NFC samples.\nTo further rule out the contribution of oxygen and to highlight the role of subsequent N, F\ndoping contribution to the activity and selectivity, we performed a dedicated control study using\noxidized carbon black (Oxidized XC72, denoted as O-XC72). In addition to the electrochemical\nevaluation, we also quantified the oxygen content in O-XC72 to confirm that it represents an\noxygen-rich carbon benchmark. As shown in Figure R11a, although O-XC72 exhibits measurable\nring currents, consistent with the known ability of oxygen-containing groups to promote partial\noxygen reduction, it delivers a much weaker H O production capability compared with NFC.\n2 2\nSpecifically, the ring current density of NFC is approximately 3.94 times higher than that of O-\nXC72 (Figure R11a), demonstrating that NFC possesses a substantially enhanced intrinsic activity\ntoward H O generation. More importantly, the product selectivity differs markedly between NFC\n2 2\nand O-XC72. The calculated H O selectivity of O-XC72 is limited to only 35–43% across the\n2 2\ntested potential range (Figure R11b), whereas NFC maintains over 95% selectivity under\ncomparable conditions. Consistently, the corresponding electron transfer number (n) for O-XC72\nremains above 3, indicating a dominant contribution from the competing 4e⁻ ORR pathway and an\ninability of oxygen doping alone to enforce a selective 2e⁻ route. In contrast, the near-2e⁻ behavior\nof NFC (high H O selectivity and n close to 2) confirms that the reaction pathway is\n2 2\nfundamentally shifted toward H O formation after the N and F doping. Furthermore, XPS analysis\n2 2\nreveals that the oxygen content in O-XC72 is as high as 16.89 at.% (Figure R11c-d), which is\nsubstantially higher than that in NFC (3.63 at.%). Despite this markedly higher oxygen\nconcentration, the 2e- ORR performance of O-XC72 is significantly inferior to that of NFC,\nindicating that a high oxygen content alone does not lead to enhanced activity or selectivity toward\nthe 2e⁻ ORR.\nTherefore, these results clearly demonstrate that oxygen functionalities contribute at most a\nbaseline activity and cannot account for the high activity and selectivity observed for NFC. As a\nR-39\nresult, the contribution of oxygen to the superior 2e⁻ ORR performance of NFC can be reasonably\nexcluded, and the pronounced enhancement is primarily attributed to the subsequent N doping and\nF-passivation. We also added this discussion as Discussion 5, Figure R11 as Figure S43, in the\nrevised Supplementary Materials.\nDiscussion 5: Exclusion of oxygen contribution to 2e- ORR performance\nTo further rule out the contribution of oxygen and to highlight the role of subsequent N, F\ndoping contribution to the activity and selectivity, we performed a dedicated control study using\noxidized carbon black (Oxidized XC72, denoted as O-XC72). In addition to the electrochemical\nevaluation, we also quantified the oxygen content in O-XC72 to confirm that it represents an\noxygen-rich carbon benchmark. As shown in Figure S43a, although O-XC72 exhibits measurable\nring currents, consistent with the known ability of oxygen-containing groups to promote partial\noxygen reduction, it delivers a much weaker H O production capability compared with NFC.\n2 2\nSpecifically, the ring current density of NFC is approximately 3.94 times higher than that of O-\nXC72 (Figure S43a), demonstrating that NFC possesses a substantially enhanced intrinsic activity\ntoward H O generation. More importantly, the product selectivity differs markedly between NFC\n2 2\nand O-XC72. The calculated H O selectivity of O-XC72 is limited to only 35–43% across the\n2 2\ntested potential range (Figure S43b), whereas NFC maintains over 95% selectivity under\ncomparable conditions. Consistently, the corresponding electron transfer number (n) for O-XC72\nremains above 3, indicating a dominant contribution from the competing 4e⁻ ORR pathway and an\ninability of oxygen doping alone to enforce a selective 2e⁻ route. In contrast, the near-2e⁻ behavior\nof NFC (high H O selectivity and n close to 2) confirms that the reaction pathway is\n2 2\nfundamentally shifted toward H O formation after the N and F doping. Furthermore, XPS analysis\n2 2\nreveals that the oxygen content in O-XC72 is as high as 16.89 at.% (Figure S43c-d), which is\nsubstantially higher than that in NFC (3.63 at.%). Despite this markedly higher oxygen\nconcentration, the 2e- ORR performance of O-XC72 is significantly inferior to that of NFC,\nindicating that a high oxygen content alone does not lead to enhanced activity or selectivity toward\nthe 2e⁻ ORR.\nTherefore, these results clearly demonstrate that oxygen functionalities contribute at most a\nbaseline activity and cannot account for the high activity and selectivity observed for NFC. As a\nR-40\nresult, the contribution of oxygen to the superior 2e⁻ ORR performance of NFC can be reasonably\nexcluded, and the pronounced enhancement is primarily attributed to the subsequent N doping and\nF-passivation.\nFor better clarification, we also added a related description to the main text on Page 19 in the\nrevised manuscript. Please see below:\nIn addition, to further exclude the possibility that enhanced 2e⁻ ORR performance originates\nfrom oxygen content, oxidized XC72 (O-XC72) with a much higher oxygen concentration was\nemployed as an oxygen-rich control. Despite containing 16.89 at.% oxygen (Figure S43c-d),\nsubstantially higher than that of Blank-C (4.7 at.%) and NFC (3.63 at.%), O-XC72 exhibits\nmarkedly lower H O activity and a limited selectivity of only 35–43%, accompanied by an\n2 2\nelectron transfer number above 3 (Figure S43a-b), indicating dominant 4e⁻ ORR behavior rather\nthan the 2e⁻ ORR. This result demonstrates that increasing oxygen content alone not only fails to\nenhance 2e⁻ ORR selectivity but may even be detrimental to H O production. Therefore, these\n2 2\nobservations confirm that oxygen contributes only a baseline activity, whereas the pronounced\nenhancement in NFC arises from the N dopants and F-passivation (More detailed discussion can\nbe obtained in Supplementary Discussion 5).\nR-41\nFigure R11. (a) LSV curves of NFC and O-XC72 in O2-saturated 0.1 M KOH electrolyte. The\ncurves are tested at 1600 rpm. (b) H O selectivity and electron transfer, (c) XPS survey, and (d)\n2 2\nelemental atomic percentage of O-XC72.\n2. The manuscript posits that spectral changes in Figure 5c support a reaction mechanism in which\nH O adsorption precedes OOH formation. This suggests that water molecules first adsorb onto the\n2\ncatalyst surface before transferring protons to O , leading to OOH generation under reducing\n2\nconditions. However, this interpretation appears inconsistent with the absence of H₂O adsorption\npeaks under nitrogen-saturated conditions in Figure 5f. Further clarification is needed to resolve\nthis discrepancy.\nResponse: We appreciate the reviewer’s insightful suggestion on this point, which significantly\nhelps us to improve the clarification of the ORR mechanism. We apologized for not thoroughly\ndiscussing the discrepancy. The apparent discrepancy between Figure 5c and Figure 5f arises\nfrom a misinterpretation of the H O-related spectral features. To clarify this discrepancy, we\n2\nrationally updated the discussion in Supplementary Discussion 6. Please see below:\nNotably, the spectral changes in Figure 5c do not indicate simple, static adsorption of H O\n2\non the catalyst surface. Instead, they reflect electrochemically activated interfacial water that\nparticipates in the oxygen reduction process under ORR conditions. As shown in Figure 5c, the\nH O emerges only under O -saturated conditions and becomes more pronounced at reducing\n2 ad 2\npotentials. This behavior indicates that H O corresponds to surface-associated water molecules\n2 ad\nthat are stabilized and activated by the ORR environment, where adsorbed O and the applied\n2\npotential induce stronger water–surface interactions. Under these conditions, H O participates in\n2 ad\nORR by facilitating proton transfer to adsorbed O , which is a prerequisite for OOH* formation.\n2 ad 2\nthan passive H O adsorption. In contrast, under N -saturated conditions (Figure 5f), although H O\n2 2 2\nis inevitably present at the electrode–electrolyte interface, it does not participate in ORR due to\nthe absence of O adsorption. Consequently, H O remains predominantly bulk-like and weakly\n2 2\ninteracting, and no stabilized H O species is formed, leading to the absence of a detectable H O\n2 ad 2 ad\nsignal.\nR-42\nTherefore, Figure 5 demonstrates that H O is a reaction-conditioned species that appears\n2 ad\nonly when H O actively participates in ORR, explaining why H O is observed in Figure 5c (at\n2 2 ad\nlower potential) but absent in Figure 5f. This observation is fully consistent with the proposed\nmechanism and does not represent a discrepancy. We sincerely hope the explanation can clarify\nthe question, and the revised manuscript can meet the reviewer’s requirements for publication.\n3. Was any change in internal resistance during stability testing taken into account when applying\niR compensation?\nResponse: We thank the reviewer’s great suggestion about the iR compensation. Actually, we also\nmonitored the internal resistance when we performed the test. Based on experimental record, after\nthe overnight electrolyte flowing, the internal resistance stabilized at approximately 0.5 Ω and\nwon’t change too much during the stability testing. To better clarify the iR compensation process,\nwe provide the detailed process below:\nTo guarantee the stable internal resistance, the electrolyzer was first assembled, and then we\nkept the KOH electrolyte flowing overnight to achieve the stable internal resistance. The iR\ncompensation was applied based on the stable internal resistance.\n4. In the RRDE performance radar chart, are H O selectivity and the number of electron transfers\n2 2\nfundamentally distinct performance metrics? Please clarify whether these parameters provide\ncomplementary or redundant information.\nResponse: We thank the reviewer for this insightful comment on the RRDE performance radar\nchart, which helps improve the clarity and completeness of our data presentation. We are pleased\nto clarify the physical meanings of the two metrics.\nAlthough both H O selectivity and the electron transfer number (n) describe the reaction\n2 2\npathway of ORR, they are not redundant. The reason why we chose the two metrics is that we\nexpected to provide a more comprehensive description of the reaction behavior. Please see the\nfollowing two reasons:\nR-43\n(a) H O selectivity directly quantifies the fraction of the total ORR current that leads to H O\n2 2 2 2\nformation via the 2e⁻ pathway. As a product-distribution metric, it reflects the catalyst’s intrinsic\npreference for H O production and the degree of competition between the 2e⁻ (H O ) and 4e⁻\n2 2 2 2\n(H O) pathways.\n2\n(b) The electron transfer number (n) represents a pathway-weighted average of electron\nconsumption and describes the overall electronic stoichiometry of the ORR. While n is\nmathematically related to selectivity, it conveys a distinct physical meaning by indicating the\naverage number of electrons transferred per O molecule during the reaction, thereby capturing the\n2\nextent of pathway mixing between the 2e⁻ and 4e⁻ routes.\nTherefore, these two parameters provide complementary information: H O selectivity\n2 2\nreflects product distribution, whereas the n-value describes electron-transfer stoichiometry and\npathway averaging. Including both metrics in the radar chart enables a multidimensional\nevaluation of 2e⁻ ORR performance, allowing a more complete and transparent comparison of\ncatalytic behavior across different samples.\nR-44\nResponse to the reviewer\nReviewer #1 (Remarks to the Author):\nThe authors have addressed all the inquiries raised by the Reviewer #3 and myself. Given the\nrigorous methodology and significant contributions of this work now, I recommend its\npublication in Nature Communications.\nResponse: Thank you for your careful evaluation and recommendation of our manuscript for\nNature Communications. We appreciate all your efforts for our manuscript.\nReviewer #2 (Remarks to the Author):\nSince the authors have addressed most of my comments, I recommend the paper for publication.\nI have one minor comment.\nFor clarity, it would be helpful to indicate in the main text that the definition of the \"stability\nscore\" is provided in the Supplementary Materials.\nResponse: Thank you for your careful evaluation and recommendation of our manuscript for\nNature Communications. We thank the reviewer’s suggestion to indicate the definition of the\n“stability score” in the main text, which helps to improve the quality of our manuscript.\nFor clarification, we added the definition into the main text as follows:\nIn addition, the stability of the (N, F)-codoped configurations was further evaluated by the\nvariations between time and energy in molecular dynamics simulations. The stability score can be\n100\ncalculated by 𝑆 = , where D , V , and J represent relative drift, variability\nrel rel norm\n1+𝐷\nrel\n+𝑉\nrel\n+𝐽norm\nrelative to range, and short-term jitter, respectively. We also added this sentence into the revised\nmanuscript and highlighted it in yellow.\nReviewer #4 (Remarks to the Author):\nAll questions have been answerd. The manuscript can be accepted.\nResponse: Thank you for your careful evaluation and recommendation of our manuscript for\nNature Communications. We appreciate all your efforts for our manuscript."}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors have addressed all the inquiries raised by the Reviewer #3 and myself. Given the rigorous methodology and significant contributions of this work now, I recommend its publication in Nature Communications.", "reviewer_2": "Since the authors have addressed most of my comments, I recommend the paper for publication. I have one minor comment.\nFor clarity, it would be helpful to indicate in the main text that the definition of the \"stability score\" is provided in the Supplementary Materials.", "reviewer_4": "All questions have been answerd.The manuscript can be accepted."}, "author_response": "Response to the reviewer\nReviewer #1 (Remarks to the Author):\nThe authors have addressed all the inquiries raised by the Reviewer #3 and myself. Given the\nrigorous methodology and significant contributions of this work now, I recommend its\npublication in Nature Communications.\nResponse: Thank you for your careful evaluation and recommendation of our manuscript for\nNature Communications. We appreciate all your efforts for our manuscript.\nReviewer #2 (Remarks to the Author):\nSince the authors have addressed most of my comments, I recommend the paper for publication.\nI have one minor comment.\nFor clarity, it would be helpful to indicate in the main text that the definition of the \"stability\nscore\" is provided in the Supplementary Materials.\nResponse: Thank you for your careful evaluation and recommendation of our manuscript for\nNature Communications. We thank the reviewer’s suggestion to indicate the definition of the\n“stability score” in the main text, which helps to improve the quality of our manuscript.\nFor clarification, we added the definition into the main text as follows:\nIn addition, the stability of the (N, F)-codoped configurations was further evaluated by the\nvariations between time and energy in molecular dynamics simulations. The stability score can be\n100\ncalculated by 𝑆 = , where D , V , and J represent relative drift, variability\nrel rel norm\n1+𝐷\nrel\n+𝑉\nrel\n+𝐽norm\nrelative to range, and short-term jitter, respectively. We also added this sentence into the revised\nmanuscript and highlighted it in yellow.\nReviewer #4 (Remarks to the Author):\nAll questions have been answerd. The manuscript can be accepted.\nResponse: Thank you for your careful evaluation and recommendation of our manuscript for\nNature Communications. We appreciate all your efforts for our manuscript."}]

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