Regulating interfacial water for oxygen transfer to benzylic C(sp^3)–H bonds via Ni-activated tungsten-oxygen covalency

Domain: neuroscience
Published: 2026-02-04
Editorial outcome: major_revision

Abstract
Recent studies on the electrocatalytic oxygen transfer from water to organic compounds have gained significant attention due to their sustainability and selectivity. However, the direct coactivation of inert hydrocarbons and water typically requires high oxidation potentials, leading to oxygen evolution reactions and low Faradaic efficiencies. Herein, a Ni-activated tungsten-oxygen covalency anode is designed for the efficient oxygen transfer from water to benzylic C(sp3)–H bonds via a Ni-regulated interfacial water structure between the anode and electrolyte. Both experimental and theoretical results reveal the critical role of W–O covalency sites with Ni-heteroatoms for boosting efficient oxygen transfer via breaking the dense interfacial hydrogen bond network and inhibiting the undesired oxygen evolution reactions, facilitating the coactivation of oxygen species and C(sp3)–H bonds. Thus, a Faradaic efficiency of >56% in a water-involved system has been achieved. This work provides important insight into designing electrocatalytic systems for inert C–H oxidation.

Introduction
The production of functional oxygenated compounds via the activation of hydrocarbons using various oxidants accounts for approximately one-quarter of all industrial catalytic processes. Moreover, over 30% of cradle-to-gate greenhouse gas emissions in chemical production can be attributed to the intensive energy input and uncontrolled overoxidation associated with traditional thermochemical methods. Recent works on the electrocatalytic oxidation of hydroxyl/carbonyl groups, hydroxyl/carbonyl-α C–H bonds, various types of biomasses and abundant hydrocarbons have demonstrated the significant potential of using water molecules as a sustainable oxygen source to produce functional organic compounds. However, the direct coactivation of even inert hydrocarbons and H2O typically requires relatively high oxidation potentials, often leading to undesirable competitive oxygen evolution reactions (OER) and overoxidation, resulting in the formation of acids and esters. Though several works have put forward strategies such as electron density regulation, oxophilicity tuning, halogen mediation, and electrolyte engineering, et al. for facilitating the oxidation of olefins while depressing the OER process and overoxidation, the activation of even inert C(sp3)–H bonds still suffers from unsatisfactory Faradaic efficiencies (FE~31%) especially in additive-free catalytic systems due to ultra-high oxidation potentials of inert C(sp3)–H bonds as compared with that of OER. It is still highly alluring to put forward efficient strategies for activating C(sp3)–H bonds for effective K/A oil production while inhibiting the OER process in a water-involved electrocatalytic system.

Herein, we show that Ni-activated tungsten-oxygen covalency (Ni-WOC) can efficiently boost the oxygen transfer from water to inert benzylic C(sp3)–H bonds via loosening the originally dense interfacial water structure and promoting the C(sp3)–H bond activation on the in situ formed tungsten-oxygen covalency, effectively producing ketones and alcohols without overoxidation products (e.g., acids and esters). A reconstruction method is suggested to prepare highly dispersed and amorphous WOC sites with better catalytic performance than crystalline WO3. Enabled by favorable lattice matching that ensures the reconstruction durability, the synergy between the Ni dopants and reconstructed WOC sites can largely disrupt the interfacial hydrogen bond network and simultaneously boost the co-activation of water molecules and C–H bonds. In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), ab initio molecular dynamics (AIMD), and density functional theory (DFT) studies reveal the critical role of Ni dopants in weakening the hydrogen bond network over the adjacent Ni-WOC species for faster oxygen transfer from water to substrates, simultaneously depressing the unwanted OER process via regulating the reaction path. Concurrently, the efficient oxidation of C(sp3)–H bonds is achieved by the coactivation of C(sp3)–H bonds and adsorbed oxygen on certain W sites of Ni-WOC. The combination of theoretical and experimental results demonstrates the boosted oxygen transfer process from water to C(sp3)–H bonds on W–O covalency via the rationally introduced Ni heteroatoms, providing a Faradaic efficiency up to >56%.

Results
To introduce uniformly dispersed Ni dopants, we employed a carbothermal method to synthesize the Ni-doped tungsten carbide (Ni/W2C) pre-catalyst by thermal pyrolysis of the mixture of ammonium metatungstate, nickel nitrate hexahydrate, and dicyandiamide, in N2 atmosphere at 1000 °C (for experimental details, please see Methods section). The Ni contents of Ni/W2C samples can be precisely tuned from 0 via 0.8 and 1.6 to 3.1 wt.% by varying the amounts of nickel nitrate hexahydrate in the precursor (Table S1). As the Ni contents increased from 0 wt.% to 3.1 wt.%, the as-formed tungsten carbide samples all exhibited a similar structure of crystalline nanoclusters supported on layered graphene with mean sizes of 3.4-3.7 nm. Accordingly, the characteristic X-ray diffraction (XRD) peaks of the (002) facet of α-phase W2C (JCPDS#35-776) gradually shifted from 38.1° to 38.6°, indicating more Ni dopants were introduced to the crystal lattice of W2C. Indeed, the uniformly dispersed Ni dopants in the crystal lattice of W2C nanoclusters have been directly revealed by the aberration-corrected high-angle-annular-dark-field scanning transmission electron microscopy (AC-HAADF-STEM) with distinguishable differences in contrast of W and Ni atoms in atomic resolution AC-HAADF-STEM images. The homogeneous distribution of Ni dopants in W2C clusters was further confirmed by corresponding energy-dispersive X-ray spectroscopy (EDS) mapping and line scan results. X-ray photoelectron spectroscopy (XPS) analysis results further confirmed the presence of W and Ni atoms mainly in the form of metallic state, aligning well with the typical electronic configuration of transition metal carbides.

The obtained Ni/W2C samples were investigated as potential anode pre-catalysts for the oxygenation of benzylic C(sp3)–H bonds on ethylbenzene via oxygen transfer from water, which is utilized as a model reaction in a homemade undivided three-electrode system (for experimental details, please see Methods section). In this system, no oxygenated products were generated without an applied bias, regardless of whether Ni/WC was used as a pre-catalyst or not. At 1.8 V vs. Ag/AgCl, the system without pre-catalysts only exhibited very low yield (<3%) and FE (<17%). However, all Ni/WC pre-catalysts with different Ni contents exhibited higher yields (from 7.8% to 10%) and FEs (from 42.3% to 45.4%) at a fixed condition within 2 h. More importantly, with optimized Ni content, the Ni1.6/WC pre-catalyst can successfully achieve the continuous oxygenation of benzylic C(sp3)–H bonds with a yield up to 90% within 48 h and a regio-selectivity of >99% to 1-Phenylethanol and acetophenone, indicating an efficient electrocatalytic oxygen transfer process. The Ni1.6/WC pre-catalyst with optimized Ni content was employed for further studies.

It should be noted that the conversion and FE for oxygenated products are closely tied to the catalyst loading, highlighting the essential role of anode catalysts in facilitating the electrocatalytic oxygen transfer process. Moreover, this oxygen transfer process can be efficiently achieved over a broad range of working potentials, from 1.6 V to 2.2 V (vs. Ag/AgCl), with satisfactory FE ranging from 47% to 56%. And the FE of 56.5% under optimized conditions is among the highest ones in currently all reported additive-free inert C(sp3)–H oxidation system using water as oxygen source, indicating more favorable oxygenation process compared with OER pathway with a FE > 50%.

The isotope labeling experiments using H2 18O further confirmed an efficient oxygen transfer process from water to C(sp3)–H bonds, with only 18O-labeled products detected. All these results reveal an electrocatalytic oxygen transfer process from water to C(sp3)–H bonds.

Interestingly, the progressive activation behavior of the pre-catalyst was observed at the earlier stage of the oxygenation reaction of ethylbenzene, manifested by a notable enhancement in catalytic activity. We thus turned our interest to the identification of real active sites. AC-HAADF-STEM images and the corresponding EDS mapping results of the used catalysts show highly dispersed and amorphous structures of W and Ni species, speaking for a reconstruction process of the W2C components to generate the real catalytic centers. The atomic-resolved AC-HAADF-STEM image of the reconstructed sample directly demonstrates the homogeneous distribution of Ni atoms over amorphous clusters, which shows the replacement of W to Ni atoms with obvious contrast difference and the comparable Ni/W–W distance without obvious loss of Ni sites. The fast degradation of metal carbide nanocrystals into an amorphous state within around 10 min was further revealed by the ex situ X-ray diffraction (XRD) analysis.

The ex situ XPS studies further suggested a migration process of oxygen species to generate WOC or Ni-WOC with W6+ or Ni2+ centers from original metallic W0 and Ni0 states, respectively. Typical peaks of adsorbed hydroxyl groups centered at 532.5 eV gradually decreased with prolonged reaction times, suggesting an oxygen transformation/transfer process from pre-adsorbed hydroxyl species to lattice oxygen for the formation of Ni-WOC, with lattice oxygen signal (530.8 eV) becoming dominant after 10 min. Specifically, at the initial stage of the reaction (1 min), a significant accumulation of hydroxyl groups at W sites was observed, serving as the primary oxygen source for the formation of lattice oxygen in the WOC structure. From 1 min to 30 min, the ratio of lattice oxygen increased from 21% to 41%, while the peak area of hydroxyl groups remained relatively constant. This indicates an ongoing oxygen species migration process where hydroxyl groups transform into lattice oxygen, converting carbide into oxide, and the consumed hydroxyl groups can be readily replenished from the electrolyte, ensuring a continuous and abundant oxygen supply throughout the reaction period. Indeed, the potential-dependent in situ Raman spectra and the ex situ Raman spectra of the reconstructed samples confirmed the formation of tungsten-oxygen species according to the ever-weakened W–C signal from 690 cm-1 to 810 cm-1 and the accumulation of W=O signal at around 940 cm-1, as well as the W–O–W signal at around 330 cm-1. All these results, that the co-retention of Ni and W sites in amorphous clusters and the significant emergence of lattice oxygen, indicate the oxygen species-migration process for the in situ formation of Ni-WOC as the possible real active sites for the oxygen transfer process.

The in situ generated highly dispersed Ni-WOC sites have provided fully exposed active sites with the essential synergy between WOC sites and uniformly dispersed Ni heteroatoms, which is of key importance for boosting the oxygen transfer process. Specifically, the yield (3.5%) and FE (24.3%) toward oxygenated products on crystalline WO3 (c-WO3) anode is slightly lower than those of pristine WOC (4.0% yield, 33.9% FE) or Ni/NC (3.7% yield, 27.3% FE) anodes, indicating a slightly promoted oxygen transfer reaction on highly dispersed WOC or Ni sites. More importantly, the Ni-WOC anode provided a yield of 10% and an FE of 45.4% under a fixed condition, which is 2.5 times the yield of the WOC anode and 2.1 times the yield of the mechanical mixture of WOC and Ni/NC. The decreased electrochemical surface area (ECSA) of Ni-WOC catalysts from 43.63 mF·cm-2 before reconfiguration to 25.01 mF·cm-2 after reconfiguration rules out the influence of ECSA on the enhanced catalytic efficiency. The well-maintained layered graphene-supported structures after reconfiguration further validate the unique role of Ni dopants, rather than any morphological changes in support, in enhancing the final catalytic performance. All these results reveal the essential importance of the in situ formation process for highly dispersed Ni-WOC sites with obvious synergy between Ni heteroatoms and WOC sites for the enhanced oxygen transfer process, which cannot be solely attributed to the existence of tungsten oxides or the changes in surface area.

The involvement of oxygen transfer in the formation of Ni-WOC also plays a crucial role in the subsequent oxygenation reaction, in which the arrangement of water molecules (the oxygen sources) at the interface between the Ni-WOC surface and electrolyte dominates the initial oxygen diffusion efficiencies. The AIMD simulation results theoretically indicated the weakened hydrogen bond (H-bond) networks over the surface Ni sites of the Ni-WOC model, manifested by the decreased number of H-bonds from 4.8 on the WOC model to 2.9 on the Ni-WOC model in the area with a vertical distance (z) of 3.36 Å from the surface Ni sites. This is to say that there is a void in the water layer over Ni sites as reflected by the absence of interfacial water in the domain with a radius (r) of 2.16 Å to Ni sites.

The loosened water network may benefit the penetration of water molecules through the Helmholtz layer to the Ni-WOC surface, as experimentally confirmed by ATR-SEIRAS analysis. At a constant working potential of 2.0 V vs. Ag/AgCl, the non-hydrogen-bonded water signal (at 3580 cm–1) predominates in the interfacial water structure over the Ni-WOC-based anode throughout the reaction period. In contrast, on the WOC-based anode, 2-coordinated hydrogen-bonded and 4-coordinated hydrogen-bonded water signals (at around 3220 cm–1 and 3400 cm–1) dominate during the reaction. The increased ratio of non-hydrogen-bonded water molecules over the Ni-WOC-based anode indicates an efficient diffusion process. It is noteworthy that, with a fixed and low concentration (0.05 M) of ClO4– in all the experiments, the ATR-SEIRAS results reveal negligible ClO4– signals in the region around 1100 cm–1 on both WOC and Ni-WOC catalyst surfaces throughout the reaction period. To further assess the universality of Ni heteroatoms in regulating the interfacial water structure, we conducted in situ ATR-SEIRAS experiments in electrolytes containing different anions, including SO42– and HPO42–. The population of weakly hydrogen-bonded water molecules on the Ni-WOC-based electrode surface increased significantly by factors of 1.63, 1.43 and 1.56 in LiClO4, K2HPO4 and K2SO4 electrolytes, respectively, as compared to those on the WOC-based electrode. These results further confirm the dominant role of Ni dopants in regulating the interfacial water structure, rather than the influence of anions. More importantly, potential-dependent distribution of relaxation times (DRT) spectra directly demonstrated the depressed diffusion resistance of oxygen species from 392.8 Ω (at 0.8 V vs. Ag/AgCl) over the WOC-based anode to 336.1 Ω over the Ni-WOC-based anode. All these results unveil the critical role of Ni heteroatoms in breaking the originally dense interfacial H-bond network and ensuring a fast oxygen diffusion process from electrolyte to adsorption sites on Ni-WOC.

We then investigated the role of Ni in modulating the active sites for pre-adsorption and activation of water molecules transferred from the electrolyte to the Ni-WOC surface. Density functional theory (DFT) calculation results reveal an upward shift in the d-band center of metal sites from –1.959 eV (WOC) to –1.902 eV (Ni-WOC) upon Ni doping. The Bader charge and differential charge density analysis results further demonstrate the role of the Ni heteroatom as an electron acceptor to attract 0.22 e– from the adjacent WOC site. Accordingly, the W atom adjacent to the Ni atom of the Ni-WOC model has the strongest coupling interaction with the pre-adsorbed water molecule with an adsorption energy of –0.921 eV. The RDF between the claimed W atom and water molecules also confirms the hydrophilic nature of this site with a W–O distance of 2.25 Å, consistent with the calculated adsorption energy. It should be noted that the Ni site is not a favorable absorption site for water molecules with an adsorption energy of 0.085 eV, matching well with the trend of water affinity revealed by the AIMD simulation results.

We further investigated the possible active oxygen species that might be derived from water for the subsequent oxygenation of C(sp3)–H bonds. The isotope reaction using D2O as the oxygen source did not provide deuterated products even with a reaction time of 4 h, excluding the direct participation of hydroxide species (*OH) or oxyhydroxide species (*OOH) during the oxygen transfer process. Another control reaction using 18O-labeled Ni-WOC as the anode electrocatalyst did not give detectable amounts of 18O-labeled products, speaking for the absorbed oxygen (*O) from water activation rather than the lattice oxygen (Olat) as the majority of the oxygen species for the oxygen transfer process over the Ni-WOC anode. This result that *O plays as an active species for inert bonds activation is consistent with previously reported cases.

After determining the adsorption site and the forms of possible active oxygen species, we turned our focus to the following coactivation of oxygen species and C(sp3)–H bonds on the Ni-WOC anode. The gradually enhanced ATR-SEIRAS signals of hydrated tungstate (centered at 1746 cm–1), distinct from regular water bending modes, observed on Ni-WOC anode at ever-enlarged working potentials higher than 1.0 V (vs. Ag/AgCl) demonstrated a more favorable diffusion process of oxygen species to Ni-WOC anode surface as compared to bare WOC anode. With a similar trend of potential induced enhancement on the pre-adsorption of ethylbenzene, the Ni-WOC anode directly triggered the transfer of oxygen to ethylbenzene via the formation of W–O–C bridge according to a more pronounced ATR-SEIRAS signal at around 1240 cm–1 of ethyl α-C bonded to metal through oxygen on the Ni-WOC anode. The potential-dependent blue shift of the W–O–C signal from 1240 cm–1 at 1.0 V (vs. Ag/AgCl) to 1246 cm–1 at 2.4 V (vs. Ag/AgCl) further indicates an intensive electrocatalyzed oxygen transfer process, which contrasts sharply with rather weak W–O–C and unactivated –CH2– (1214 cm–1) signals on the WOC anode. To further validate the proposed oxygen transfer process, we conducted potentiostatic in situ ATR-SEIRAS experiments at 2.0 V versus Ag/AgCl both before and after the addition of ethylbenzene to track the emergence of key intermediates. The ever-existing signals of hydrated tungstate at 1746 cm–1 both before and after the addition of ethylbenzene indicate the strong affinity of W sites for water, facilitating subsequent water activation. Additionally, an emergent band corresponding to the C–C stretching mode of ethylbenzene near 1040 cm–1 after the addition of ethylbenzene further confirms the efficient adsorption of ethylbenzene on Ni-WOC. Following the facile adsorption of water and ethylbenzene, the emerged signals at the region near 1246 cm–1 after adding ethylbenzene have indicated a C–H activation process through the formation of W–O–C structure. Collectively, the Ni heteroatoms boost facile water adsorption on neighboring W sites and thus promote C–H activation by forming W–O–C intermediate on the Ni-WOC-based electrode. These results indicate that the oxygen transfer process is induced by the coactivation of water and C–H bonds boosted by Ni heteroatoms, while the formation of the W–O–C structure plays a key intermediate role in the oxygen transfer process.

Theoretically, we further investigated the possible role of Ni-WOC in regulating reaction pathways from OER to oxygenation of C(sp3)–H bonds. As revealed by DFT calculations, the energy barrier of each step for the formation of *O as active oxygen species on the Ni-WOC model has decreased dramatically. The DRT spectra also indicate improved reaction kinetics, corresponding to a timescale of 10–3 s at the cathode upon introducing Ni dopants. The kinetic impedance is reduced to 8.0 Ω for the Ni-WOC catalyst, compared to 14.0 Ω for the WOC catalyst. The integration of theoretical and experimental results highlights the crucial role of Ni dopants in efficiently activating water molecules for generating active oxygen species from an intrinsic kinetics perspective. However, as the DFT calculation suggested, the ΔG value for the hydroxylation step from *O to *OOH as the rate-determining step (RDS) for OER has increased from 3.02 eV on the WOC model to 3.33 eV on the Ni-WOC model. Experimentally, the suppression of OER by Ni doping is directly evidenced by the decrease in FE for O2 from 55.2% on the WOC-based electrode to 34.1% on the Ni-WOC-based electrode. More importantly, the ΔG value for the adsorption of ethylbenzene with the formation of *O on the Ni-WOC model is as low as 2.83 eV, making it more favorable for the oxygenation of C(sp3)–H bonds rather than the formation of *OOH from *O in OER. The displacement of OER by ethylbenzene oxidation is further experimentally manifested by linear sweep voltammetry curves, where both the appearance of a distinct oxidation peak at 1.72 V (vs. Ag/AgCl) and a simultaneous decrease in the OER current after adding ethylbenzene into the original water-based electrolyte were observed. Additionally, the isotope kinetic effect (KIE) was also tested to reveal the changes of the rate-determining step. The calculated KIE value (jH/jD, jH: the current density measured in H2O-based electrolyte, and jD: the current density measured in D2O-based electrolyte) at 1.72 V (vs. Ag/AgCl) decreases from 1.40 (OER alone) to 1.22 (with ethylbenzene), indicating that the isotopic effect of water oxidation becomes less dominant when C–H activation and oxidation are involved. All these results have clearly elucidated the essential role of Ni heteroatoms in boosting the coactivation of water and C(sp3)–H bonds while suppressing the undesired OER process (from *O to *OOH) from an intrinsic kinetics perspective, well explaining the high FE values for producing oxygenated compounds as supported by both theoretical and experimental evidence.

Taken together, the Ni heteroatoms regulate interfacial water structure for fast oxygen diffusion from electrolyte to Ni-WOC surface, simultaneously boosting the coactivation of oxygen species and C(sp3)–H bonds on W–O covalency sites with inhibited OER process. In this way, the Ni-WOC-based anode has provided satisfactory FEs ranging from 43.2% to 64.8% in a general scope of benzylic C(sp3)–H bonds, including secondary (Ethylbenzene, Propylbenzene) and tertiary (iso-Propylbenzene, Diphenylmethane) C(sp3)–H bonds with electron-withdrawing (3-Ethyl-Fluorobenzenen) or donating (o-Ethyltoluene, p-Ethyltoluene) groups. It should be noted that the current substrate scope is still limited to benzylic C(sp3)–H bonds, and the near-unity regioselectivity is governed by the inherent reactivity of the benzylic site itself, requiring further research to expand this promising oxygen transfer system.

Additionally, Ni-WOC-based anode has provided durable capability for oxygen transfer from water to C(sp3)–H bonds with high FEs (from 55.2% to 58.4%) for oxygenated products without obvious decay in catalytic performance for more than 6 circles of reuse. More importantly, after a long-term electrolysis, the Ni-WOC structure remains durable with abundant amorphous features revealed by TEM and XRD. XPS analysis indicates a raised Ni2+/Ni0 ratio from 0.15 to 10.11 and W6+/W0 ratio from 0.37 to 21.22, along with the significant emergence of lattice oxygen. The EDS mapping confirms the homogeneous distribution of Ni atoms over the whole support of the spent catalyst. Quantitative EDS spectra and the inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis results further demonstrate the consistent Ni/W atomic ratios before (0.095 via ICP-AES) and after (0.086 via ICP-AES and 0.107 via EDS) long-term uses, speaking for the co-retention of Ni-W complex during the long-term electrolysis.

Besides the excellent capability and durability, the Ni-WOC-based electrocatalytic devices utilizing water as an oxygen source for additive-free oxygenation of inert C(sp3)–H bonds are competitive when compared with the state-of-the-art electrocatalytic systems reported in the literature. Taking ethylbenzene as an example, the Ni-WOC-based anode has provided a satisfactory FE up to 58.4%. And a continuous oxygen transfer process for a high yield up to 90% has been achieved on Ni-WOC-based anode, which is among the competitive ones in the currently reported cases. Accordingly, the Ni-WOC-based anode has exhibited an energy efficiency (ηE) of 10.9 mol/kW·h. Additionally, the additive-free feature of the Ni-WOC anode has significantly reduced the costs associated with material and product purification.

Methods
Synthesis of Ni/W2C and W2C pre-catalysts
Synthesis of Ni/W2C. Typically, 0.50 g ammonium metatungstate and 10.00 g dicyandiamide were mixed with different contents of nickel (II) nitrate hexahydrate (23.60, 47.20, 94.40 mg) in 50 mL deionized water. The mixture was heated at 80 °C under continuous stirring to remove the water. The obtained homogeneous solid mixture with a light green color was ground into powder and transferred into a cylindrical crucible with a lid. The crucible with the precursor was heated at 1000 °C for 2 h with a heating rate of 2.5 °C min−1 under a highly pure nitrogen gas atmosphere. The final product was collected after naturally cooling down and denoted as Ni0.8/W2C (with 23.60 mg nickel nitrate hexahydrate), Ni/WC (with 47.20 mg nickel nitrate hexahydrate), and Ni3.1/W2C (with 94.40 mg nickel nitrate hexahydrate), respectively.

Synthesis of W2C. The synthesis of W2C follows the same procedure as that of Ni/W2C, with the exception that nickel nitrate hexahydrate is omitted from the precursor.

Synthesis of c-WO3 catalysts
The crystalline WO3 was synthesized by heating the monoclinic WO3·H2O, which was obtained by the Freedman method. Typically, 10 mL of 1 M Na2WO4·2H2O was added to 90 mL of 3 M HCl. The as-formed yellow mixture was stirred overnight at 300 rpm at room temperature. The sample obtained was collected via vacuum filtration and washed with deionized water until the pH of the rinsed solution reached approximately 6. The obtained yellow powder was dried at 60 °C overnight to get the monoclinic WO3·H2O. The monoclinic WO3 was obtained by heating WO3·H2O at 350 °C for 5 h in air with a heating rate of 5 °C min−1. The final product collected after naturally cooling down was denoted as c-WO3. The XRD patterns of the synthesized WO3·H2O and WO3 samples have demonstrated their crystalline structure, as shown in Fig. S2c, d.

Synthesis of Ni/NC catalysts
Briefly, the urea was heated to 550 °C for 4 h in air with the heating rate of 2.3 °C/min to form the polymeric carbon nitride (PCN). 6.19 g PCN powder was mixed with a homogeneous mixture of 48.7 mg nickel (II) nitrate hexahydrate, 0.91 g 1,4-benzenedicarboxylic acid and 0.64 g triethylenediamine in N,N-dimethylformamide (DMF) solution. The resulting solid powder after removing solvent was heated to 900 °C for 1 h with a heating rate of 1.5 °C/min under an N2-protected atmosphere. The obtained black solid samples were denoted as Ni/NC.

Preparation of working electrodes
The catalyst ink was prepared by mixing 10 mg corresponding catalyst and a solution containing 300 μL Nafion solution (5%), 700 μL deionized water, and 1400 μL Ethanol. The obtained mixture was sonicated for 2 h to get a homogeneously dispersed ink.

The working electrode was prepared by homogeneously dipping specific volumes of the ink onto a 2 × 2 cm2 carbon cloth, followed by drying at 120 °C for 1 h. The as-obtained electrode was used for further electrocatalytic tests.

Electrocatalytic oxygen transfer reaction tests
All the electrocatalytic experiments were performed in a homemade undivided cell with a three-electrode system (Fig. S33) on a potentiostat (CHI 660E, Shanghai CH Instruments Company). Working electrodes (the anode) were composed of catalysts supported on a carbon cloth. A Titanium (Ti) mesh with a size of 2 × 2 cm2 and an Ag/AgCl electrode was employed as the cathode and reference electrode, respectively. For the oxygen transfer reaction, the potentiostatic test was conducted in an Ar-saturated electrolyte composed of water/sulfolane solution containing 25 mM ethylbenzene and 50 mM LiClO4. The sulfolane was used as a bipolar solvent to improve the homogeneous dispersion of the ethylbenzene phase in the electrolyte. The influence of the volume ratio of sulfolane was shown in Fig. S8.

The electrocatalytic continuous oxygen transfer reaction was conducted continuously for 48 h without intervals. The electrocatalytic stability tests of electrodes for oxygen transfer reaction were evaluated via six repeated cycles at the same working potential, with each cycle of 2 h.

The generated anode products were analyzed by GC-MS (Shimadzu QP2010SE equipped with SH-Rxi-5Sil MS column) to determine the components of products and calculate the yield and Faradaic efficiency.

The Faradaic efficiency (FE) was calculated as follows:
FE (%) = (Ni × n × F / Q) × 100%
where Ni (mole) is the number of moles for the specific product (alcohols and ketones); n is the number of electrons exchanged for product formation, which is 2 for alcohols and 4 for ketones; F is the Faradaic constant of 96485 C mol−1; Q is the measured passed charge.

The energy efficiency (ηE) was calculated as follows:
ηE (mol kW−1 h−1) = N / W
where N (mole) is the number of moles for the conversed substrates; W (kW·h) is the consumed electronic work during the electrocatalytic process.

Electrochemically active surface area measurement
The electrochemically active surface area (ECSA) of the catalysts, both before and after the reconstruction, was measured in 0.1 M KOH electrolyte using the cyclic voltammetry method. Working electrodes (the anode) were composed of catalysts supported on a 2 × 2 cm2 carbon cloth. A Titanium (Ti) mesh with a size of 2 × 2 cm2 and an Ag/AgCl electrode was employed as the cathode and reference electrode, respectively. For the fresh catalysts, the cyclic voltammetry was performed by scanning from 0.816 V (vs. Ag/AgCl) to 0.916 V (vs. Ag/AgCl) at scanning rates of 2, 4, 6, 8, 10, and 15 mV·s-1. The ECSA measurement for reconstructed samples follows the same procedure, with the exception that the working electrode was changed to a reconstructed one. The ECSA was calculated as follows:
ECSA = Cdl / Cs
where Cdl is the double layer capacitance measured from cyclic voltammetry method; Cs is the reference capacitance.

In situ Raman spectroscopy studies
The in situ Raman measurements were conducted on a Renishaw inVia Qontor Raman microscope using a custom-designed in situ electrochemical cell (Fig. S34a). Specifically, the measurements were performed using a 532 nm semiconductor laser at 2.5 mW power and a 50× microscope objective, with frequencies calibrated against silicon wafers beforehand. The experiments utilized an undivided three-electrode cell equipped with an embedded quartz window. The electrode configuration consisted of a platinum wire counter electrode, an Ag/AgCl reference electrode, and a working electrode made from carbon cloth loaded with catalyst at 1 mg cm−2. Water-sulfolane mixture (volume ratio of 3:1) with 25 mM ethylbenzene and 50 mM LiClO4 was used as electrolyte. A potentiostat (Vertex.C, Ivium Technologies B.V.) was used to control the potential during the Raman test. Each spectrum in the in situ potentiodynamic Raman test under different applied bias ranging from 0.4 V to 1.8 V (vs. Ag/AgCl) was collected for approximately 10 min every 0.2 V.

In situ infrared absorption spectroscopy studies
The attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) measurements were run on a Nicolet iS50 FTIR spectrometer equipped with an HgCdTe (MCT) detector using a custom-designed in situ electrochemical cell (Fig. S34b). All measurements are conducted at the Kretschmann configuration, incorporating an Au film-coated Si window with catalyst ink dropped on it. The Au film functions both as a current collector and a SEIRA-active substrate, enabling in situ analysis of the anode/electrolyte interfaces close to the catalyst with high sensitivity. Water-sulfolane mixture (volume ratio of 3:1) with 25 mM ethylbenzene and 50 mM LiClO4 was used as electrolyte, with an Ag/AgCl electrode and a Pt mesh as the reference electrode and cathode, respectively. The IR spectra were collected with p-polarized IR radiation at the spectral resolution of 8 cm−1. The incidence angle is ca. 60°. All spectra were shown in the absorbance unit as −log(I/I0), where I and I0 represent the intensities of the reflected radiation for the sample and reference single-beam spectra, respectively.

In situ potentiostatic ATR-SEIRAS spectra for the surface water structure were collected continuously at working conditions (2.0 V vs. Ag/AgCl) every 2 min. The whole experimental period is 30 min.

In situ potentiodynamic ATR-SEIRAS spectra for the oxygen transfer process at a scan rate of 5 mV·s−1 were continuously collected every 200 mV at the cell voltage from 0.2 to 2.4 V (vs. Ag/AgCl).

In situ potentiostatic ATR-SEIRAS spectra for the oxygen transfer process at a constant working potential of 2.0 V vs. Ag/AgCl were continuously collected every 1 min. The ethylbenzene was added to the in situ electrochemical cell between 9 and 10 min.

Each single-beam spectrum was averaged from 32 scans, corresponding to a period of ca. 14 s. The concentration of LiClO4 (50 mM) was fixed throughout all experiments to rule out the potential influence of anions on water structure.

Distribution of relaxation times analysis
Potentiostatic electrochemical impedance spectra (EIS) were collected in the range from 0.1 Hz to 1 MHz every 0.2 V at the bias ranging from 0.4 to 1.6 V (vs. Ag/AgCl) (see Fig. S19). To determine the oxygen species diffusion process over the Ni-WOC anode, 1 M KOH was used as the electrolyte. The distribution of relaxation times (DRT) is used to analyze the EIS data.

DRT impedance, ZDRT(f), at a frequency f, can be expressed as
ZDRT = R∞ + ∫ γ(lnτ) / (1 + i2πfτ) dlnτ
Where R∞, τ, γ(lnτ) and f are the ohmic resistance, relaxation time, distribution function of relaxation time, and frequency, respectively. Moreover, polarization resistance, Rpol, is computed by:
Rpol = ∫ γ(lnτ) dlnτ

Density functional theory calculations
Density functional theory (DFT) calculations were conducted utilizing the Vienna Ab Initio Simulation Package (VASP). The generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) of exchange-correlation functional was employed. The DFT-D3 method was employed to incorporate van der Waals interactions. A plane-wave expansion with a kinetic energy cutoff of 450 eV was employed. The convergence criteria for energy and force were set to 10−5 eV and 0.02 eV Å−1, respectively. K-points were set to 3 × 3 × 1 for geometry optimization and energy calculation. A vacuum layer with a thickness of 15 Å along the z-direction was applied to avoid unreasonable interactions among periodical images along the z-direction.

The amorphous W–O covalency model was constructed by using ab initio molecular dynamics. Briefly, the originally crystalline Ni-doped WO3 model was treated using ab initio molecular dynamics by VASP with all layers fully relaxed. The system was maintained at 600 K in an NVT ensemble framework to obtain the amorphous structure. The total duration of the AIMD simulation reached 5 ps.

The Gibbs free energy change for each step of the oxidation reaction was calculated as follows:
ΔG = ΔE + ΔZPE − TΔS (T = 298.15 K)
where ΔE, ΔZPE, and ΔS are the changes in the reaction energy, zero-point energy, and entropy, respectively. Each step and the corresponding ΔG values of the OER and oxygenation pathway are listed in Tables S5 and 6.

Ab initio molecular dynamics simulation
The ab initio molecular dynamics (AIMD) simulation for the structure of interfacial water over the Ni-WOC and WOC models was carried out using the open source CP2K/Quickstep package based on a hybrid Gaussian plane wave (GPW) scheme. The orbitals are described by an atom-centered Gaussian-type basis set. An auxiliary plane wave basis set with a cutoff energy of 400 Ry is used to re-expand the electron density in the reciprocal space. Perdew-Burke-Ernzerhof (PBE) functional with DFT-D3 dispersion correction was used. The core electrons were represented by analytic Goedecker-Teter-Hutter (GTH) pseudopotentials. For valence electrons, the Gaussian basis sets were double-ζ basis functions with one set of polarization functions (DZVP).

The initial model of catalyst/water interfaces was constructed using the previously obtained amorphous W–O covalency model for DFT calculations. The simulation cell was filled with 116 water molecules and a vacuum layer of approximately 20 Å in z-direction. The entire simulation cell has a size of 15.44 × 15.44 × 46.00 Å3 as shown in Fig. S15.

All AIMD simulations were performed in the NVT ensemble, with Nosé–Hoover chain thermostat to keep a constant temperature of 298.15 K. A time step of 0.5 fs was adopted for the Velocity-Verlet algorithm. The structural relaxation process lasted for 2 ps to obtain equilibrium configurations, followed by a simulation of 10 ps for the production process used for the final analysis. The simulation was conducted in periodic boundary conditions.

The hydrogen bond analysis follows a typical criterion of a 30° angle cutoff and a 3.5 Å bond length cutoff. To ensure the accuracy of the simulation, all presented results are statistical averages calculated over a 10 ps simulation, corresponding to 20,000 steps. This extensive sampling effectively filters out any anomalous simulation artifacts. Additionally, simulations of both the Ni-WOC and WOC models were conducted under identical conditions, providing clear evidence of the disruption of hydrogen bond networks near the doped Ni sites.

Structural characterization
Aberration-corrected high-angle annular dark field scanning transmission (AC-HAADF-STEM) images were recorded on a Hitachi HF5000 scanning/transmission electron microscope at an acceleration voltage of 200 kV with a probe spherical aberration corrector. The corresponding Energy Dispersive X-ray Spectra (EDS) were collected by an INCA X-Max 80 TEM EDS spectrometer. Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and HAADF-STEM images were recorded by a Talos F200X G2 microscope with an acceleration voltage of 200 kV. Powder X-ray diffraction (XRD) patterns were recorded on a Rigaku Miniflex 600C X-ray diffractometer with Cu Kα radiation (λ = 1.5418 Å) and operated at a scan rate of 5° min−1. X-ray photoelectron spectroscopy (XPS) experiments were performed using a Kratos Axis Ultra DLD spectrometer with monochromated Al Kα radiation. The inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurement was conducted on an iCAP 6300 spectrometer for metal element analysis. The Raman spectroscopy was conducted on a Renishaw inVia Qontor Raman microscope with the laser wavelength of 532 nm.

Data availability
All the relevant data are included in this paper and its Supplementary Information. The data that support the findings of this study are available from the corresponding authors upon request. Source data are provided with this paper.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The core objective of this research is to achieve highly efficient oxygen transfer from electrocatalytic water to the inert benzylic C(sp³)-H bond. The study proposes a strategy utilizing Ni-activated tungsten-oxygen covalent bond (Ni-WOC) to regulate the interfacial water structure, addressing the challenges of severe OER competition and low Faradaic efficiency prevalent in conventional systems. Additionally, broader applicability, technoeconomic relevance, and quantitative characterization of the catalyst structure evolution of this research require further elaboration. The authors must address the following questions:\n1、 The DFT calculation only provides the adsorption energy of water on the W site (-0.921 eV), but fails to quantify the electronic state changes in the W atom induced by Ni doping, such as the Bader charge transfer on the W atom or the shift of the d-band center. Consequently, it is impossible to explicitly clarify how the electron transfer regulates the binding energy between W and oxygen species (*O, *OH). It is suggested that the authors supplement the analysis with Density of States plots, Differential Charge Density maps, and quantify the electronic interaction between Ni and W. This would elucidate the electronic essence of \"Ni-activated W-O covalency,\" preventing the mechanism from remaining at the level of macroscopic phenomena description.\n2、 Is there evidence of catalyst degradation or morphology change post-operation (e.g., from XPS/XRD/SEM/ICP-OES)? Quantitative data would help.\n3、 The manuscript pointed out that Ni doping is a key factor in regulating interfacial water structure, but the influence of electrolyte ion type has yet to be tested. Can Ni doping consistently regulate interfacial water structure across different anion environments? It is recommended to supplement ATR-SEIRAS data from various anion systems to validate its universality.\n4、 The manuscript only tested benzylic compounds and did not extend the study to non-benzylic inert C(sp³)-H bonds (e.g., cyclohexane). It is recommended to expand the substrate scope to non-benzylic inert C(sp³)-H bond compounds and supplement the corresponding FE and yield data. This is crucial for clarifying whether the Ni-WOC selectivity toward benzylic sites primarily originates from the electronic effect of the benzene ring.\n5、 In the comparative analysis of the catalyst's performance, the number of reference samples selected is insufficient. This may result in an inadequate scope for comparison, making it difficult to fully support the objectivity and universality of the research conclusions. It is recommended to appropriately expand the number of comparative references, prioritizing high-impact and representative research achievements from the past five years within this field for comparison, to enhance the study's persuasiveness and depth.\n6、 The current analysis of catalyst performance lacks key characterization that directly reveals the mechanistic role of the Ni element in active site formation. It is recommended to supplement the study with in situ Raman spectroscopy measurements of Ni-WOC and WOC. This will explicitly clarify the regulatory role of Ni introduction on the catalyst's surface electronic structure, active species formation, and reaction pathway, thereby providing direct spectroscopic evidence.", "reviewer_2": "The manuscript reports an oxygen transfer process boosted by operando evolved “Ni-activated tungsten-oxygen covalency”. This work achieves an impressive Faradaic efficiency up to 56% along with near-unity regioselectivity for the oxygenation of benzylic C(sp3)–H bonds under the additive-free and water-containing conditions. I appreciate the authors’ comprehensive investigation into the catalyst structure evolution, water structure regulation, and the entire oxygen transfer path using extensive in-situ and ex-situ spectroscopic techniques. The authors have clarified the whole oxygen transfer process with several isotope-labeling and parallel in-situ spectroscopic experiments, providing valuable insights for further related works. Thus, I would like to recommend this interesting work for publication at Nature Communications after addressing the following concerns.\n1. Though the depressed OER performance is manifested by the increased Faradaic efficiency of the C–H oxygenation process, a direct quantification of oxygen gas evolution is still necessary to validate this result.\n2. The XPS data in Figure 3d-f are crucial for tracking the catalyst reconstruction. For clarity, it would be beneficial to explicitly state the atomic ratios (e.g., W6+/W0, Ni2+/Ni0, lattice/adsorbed oxygen) in the main text or a supplementary table at each time point to quantitatively support the description of the oxygen migration process.\n3. The electrochemical surface area (ECSA) is important for ruling out morphological contributions to the enhanced catalytic performance. The authors should provide full experimental details of the ECSA measurements, including the electrolyte composition and potential scan range.\n4. The assignment of the active oxygen species as adsorbed oxygen (*O) is supported by both experimental and theoretical evidence. This finding aligns with several recent reports (e.g., J. Am. Chem. Soc. 2025, 147, 26254–26266; Nat. Rev. Chem. 2024, 8, 277–293), and citing these works would help strengthen the mechanistic claims.\n5. The absence of deuterated products in D2O isotope-labeling experiments suggests that *OH or *OOH species are not directly involved in oxygen transfer. While this may hold for alcohol formation, the pathway to acetophenone could involve dehydration of peroxidic intermediates. Though, as a minor product, the ketone formation pathway is still important for strengthening the mechanistic discussion.\n6. A brief discussion about the observed diversity in yields or FEs in the substrate scope study is necessary.\nAnd some minor editorial suggestions:\n1. The inset of Figure 2b is mentioned but not clearly labeled in the caption. Please specify what the inset shows.\n2. Please ensure all abbreviations are defined upon first use (e.g., DRT is defined in the caption of Figure 4 but should also be defined when first mentioned in the main text).", "reviewer_3": "In this manuscript, the authors report a Ni-WOC catalyst generated by the in-situ electrochemical oxidation of a Ni–W₂C pre-catalyst, which exhibits high efficiency for the oxidation of benzylic C(sp³)–H bonds into the corresponding alcohols and ketones. Based on combined experimental and theoretical results, the authors propose that Ni doping significantly weakens the interfacial hydrogen-bond network of water, facilitates water adsorption and dissociation on W sites adjacent to Ni to form active *O species, and thus suppresses the OER pathway while promoting C–H bond oxidation of the organic substrate. The discovery that Ni doping modulates the interfacial water structure and reaction pathway is indeed interesting and potentially important. However, several key mechanistic aspects remain insufficiently clarified and merit further explanation.\n1. The manuscript does not provide sufficient structural evidence for the Ni-WOC catalyst. How is the coordination environment of Ni and W confirmed? Is Ni atomically dispersed within the WOC structure? Without clear structural information, the theoretical models adopted in this work lack credibility, and consequently, the derived mechanistic conclusions are questionable. Admittedly, obtaining precise structural information for the Ni-WOC catalyst is extremely challenging, as it is in-situ generated during electrolysis and is amorphous in nature. Nevertheless, at least indirect structural evidence (e.g., XAS, EXAFS, or HAADF-STEM) is expected to support the proposed Ni–O–W configuration.\n2. The manuscript lacks a clear explanation of the design logic behind the Ni-WOC system. Why was Ni-doped W₂C chosen as the catalyst precursor? What is the rationale for combining Ni and W? Why not directly prepare a Ni-doped metal oxide catalyst instead of starting from a carbide precursor? A discussion of the design concept and motivation would significantly strengthen the work.\n3. Does the oxidation state of Ni in Ni-WOC change after catalysis? The manuscript does not present post-reaction or recycled catalyst characterizations. Could Ni be oxidized to Ni³⁺ during operation? Such information is crucial to understanding the stability and real active state of the catalyst.\n4. The results suggest that the truly active site is the W center adjacent to Ni. Please provide a molecular-level explanation of how Ni modulates the Ni–O–W interface. Could other transition metals play a similar role? A comparative discussion would make the mechanistic proposal more convincing.\n5. The proposed oxidation pathway of ethylbenzene is not clearly explained. According to the current DFT results, the substrate is adsorbed at the W site adjacent to Ni, loses an electron, undergoes benzylic C–H bond homolysis to form *C₈H₉, which is then oxidized by *O to *C₈H₉O, and finally gains a hydrogen to form the alcohol product.\nMy question is: Where does this final hydrogen come from? If it originates from solvent water, why were no D₂O-labeled products detected in isotope-labeling experiments? If not from water, what is the hydrogen source? Please provide evidence or additional discussion.\n6. The oxidation process involves multiple steps, including water oxidation to *O, ethylbenzene oxidation to *C₈H₉O, and further oxidation of *C₈H₉O by *O. Which step is rate-determining? What are the kinetic isotope effect (KIE) values for these steps? Kinetic analysis is essential to support the proposed mechanism.\n7. The regioselectivity mentioned in the manuscript is not appropriate. The preferential oxidation at the benzylic C–H position results from its inherently higher reactivity, rather than a catalyst-induced regioselective effect. This term should be revised or clarified.\n8. The reaction yields both alcohol and ketone products, and the ketone is likely derived from further oxidation of the alcohol. Since two products are obtained simultaneously rather than one dominant product, the description of a “selective oxygenation process” is not accurate.\n9. In the conclusion, the statement “Ni heteroatoms disrupt the water structure … facilitating the rapid diffusion of oxygen species to the W–O covalency sites of Ni-WOC” is unclear. What exactly does “oxygen species” refer to — water molecules, *O, or other intermediates? This should be explicitly defined.\nDue to the above unresolved and critical issues, I do not recommend publication of the manuscript in its current form. However, if the authors can adequately address these points with convincing structural, mechanistic, and kinetic evidence, I would recommend resubmission to Nature Communications after major revision."}, "author_response": "Responses (R) to Comments (C)\nReviewer #1:\nThe core objective of this research is to achieve highly efficient oxygen transfer from\nelectrocatalytic water to the inert benzylic C(sp3)-H bond. The study proposes a strategy\nutilizing Ni-activated tungsten-oxygen covalent bond (Ni-WOC) to regulate the interfacial\nwater structure, addressing the challenges of severe OER competition and low Faradaic\nefficiency prevalent in conventional systems. Additionally, broader applicability,\ntechnoeconomic relevance, and quantitative characterization of the catalyst structure\nevolution of this research require further elaboration. The authors must address the\nfollowing questions:\nC1: The DFT calculation only provides the adsorption energy of water on the W site (-0.921\neV), but fails to quantify the electronic state changes in the W atom induced by Ni doping,\nsuch as the Bader charge transfer on the W atom or the shift of the d-band center.\nConsequently, it is impossible to explicitly clarify how the electron transfer regulates the\nbinding energy between W and oxygen species (*O, *OH). It is suggested that the authors\nsupplement the analysis with Density of States plots, Differential Charge Density maps,\nand quantify the electronic interaction between Ni and W. This would elucidate the\nelectronic essence of \"Ni-activated W-O covalency,\" preventing the mechanism from\nremaining at the level of macroscopic phenomena description.\nR1: According to the reviewer’s constructive suggestion, we calculated the densities of\nstates and the Bader charges (Figure S20-21 in the revised supplementary information) of\nthe Ni-WOC model and bare WOC model. The partial density of states reveals an upward\nshift in the d-band center of metal sites (Figure S20 in the revised supplementary\ninformation) from –1.959 eV (WOC) to –1.902 eV (Ni-WOC). The Bader charge (Figure\nS21a-c) and differential charge density (Figure S21d) analysis results further demonstrate\nthe role of Ni heteroatoms as an electron acceptor to attract 0.22 e– from the adjacent\nWOC sites (W1 in Figure 5a and Figure S21). The as-formed electron-deficient W1 site\nbenefits following water adsorption and subsequent C–H activation via W–O–C\nintermediate formation. All these results have been added as Figure S20-21 in the revised\nsupplementary information and fully discussed in the revised main text to elucidate the role\nof Ni in the electronic structure modulation.\nC2: Is there evidence of catalyst degradation or morphology change post-operation (e.g.,\nfrom XPS/XRD/SEM/ICP-OES)? Quantitative data would help.\nR2: Expert comments. To gain insight into the structural evolution of the catalyst rigorously,\nwe performed a comprehensive characterization of the reconstructed catalyst collected\nafter a 48-hour electrochemical test. The spent Ni-WOC catalyst remains amorphous\naccording to the TEM observation (Figure S31b in the revised supplementary information),\nin contrast to the crystalline feature of the pre-catalyst (Figure S31a in the revised\nsupplementary information). The loss of crystallinity is further corroborated by the XRD\nresults (Figure S32 in the revised supplementary information), which show the degradation\nof the characteristic (002) W C peak after long-term electrolysis. XPS analysis indicates\n2\nsignificant changes in catalysts’ chemical states, including the raised Ni2+/Ni0 ratio from\n0.15 to 10.11 and W6+/W0 ratio from 0.37 to 21.22 (Figure S33a-b and Table S3 in the\nrevised supplementary information), along with the significant emergence of lattice oxygen\n(Figure S33c in the revised supplementary information). These results, together with\npreviously provided AC-STEM-HAADF (Figure 3a-b in the manuscript), ex-situ XPS\n(Figure 3f-h in the manuscript), and Raman spectra (Figure S11 in the supplementary\ninformation) results, collectively reveal a pronounced structural transformation of the pre-\ncatalyst during electrolysis and help identify the true active species.\nFurthermore, the structural stability of the reconfigured catalyst is further tested. EDS\nmapping (Figure S31e-f in the revised supplementary information) confirms the\nhomogeneous distribution of Ni atoms over the whole support of the spent catalyst.\nQuantitative EDS spectra (Figure S31d and Table S8 in the revised supplementary\ninformation) and the ICP-OES (Table S8) analysis results demonstrate the consistent Ni/W\natomic ratios before (0.095 via ICP-OES) and after (0.086 via ICP-OES and 0.107 via EDS)\nlong-term uses, rather speaking for the co-retention of Ni-W complex during the long-term\nelectrolysis. We have incorporated these results in the revised supplementary information\nas Figure S31-33, Table S3, and Table S8, and discussed in the revised main text to clarify\nthe structural reconfiguration and the robustness of active sites.\nC3: The manuscript pointed out that Ni doping is a key factor in regulating interfacial water\nstructure, but the influence of electrolyte ion type has yet to be tested. Can Ni doping\nconsistently regulate interfacial water structure across different anion environments? It is\nrecommended to supplement ATR-SEIRAS data from various anion systems to validate its\nuniversality.\nR3: Insightful comment. To assess the universality of Ni heteroatoms in regulating the\ninterfacial water structure, we conducted in-situ ATR-SEIRAS experiments in electrolytes\ncontaining different anions including SO 2– and HPO 2– (Figure S17 in the revised\n4 4\nsupplementary information). The population of weakly hydrogen-bonded water molecules\non the Ni-WOC-based electrode surface increased significantly by factors of 1.63, 1.43\nand 1.56 in LiClO , K HPO and K SO electrolytes, respectively, as compared to those on\n4 2 4 2 4\nthe WOC-based electrode (Figure S18 in the revised supplementary information). All these\nresults unambiguously reveal the unique but universal role of Ni heteroatoms of Ni-WOC\ncatalysts in constructing disrupted interfacial hydrogen bond network. The corresponding\ndata have been included as Figure S17-18 in the revised supplementary information and\nare briefly discussed in the main text.\nC4: The manuscript only tested benzylic compounds and did not extend the study to non-\nbenzylic inert C(sp3)-H bonds (e.g., cyclohexane). It is recommended to expand the\nsubstrate scope to non-benzylic inert C(sp3)-H bond compounds and supplement the\ncorresponding FE and yield data. This is crucial for clarifying whether the Ni-WOC\nselectivity toward benzylic sites primarily originates from the electronic effect of the\nbenzene ring.\nR4: Thoughtful comment. We conducted electrochemical experiments using cyclohexane\nwithout detectable oxidation products, validating the reviewer’s prediction that\nregioselectivity is governed by the benzene ring itself. We have added detailed discussion\non this point to Page 16 Line 366-369 of the revised main text.\nC5: In the comparative analysis of the catalyst's performance, the number of reference\nsamples selected is insufficient. This may result in an inadequate scope for comparison,\nmaking it difficult to fully support the objectivity and universality of the research conclusions.\nIt is recommended to appropriately expand the number of comparative references,\nprioritizing high-impact and representative research achievements from the past five years\nwithin this field for comparison, to enhance the study's persuasiveness and depth.\nR5: Kind suggestion. We have included more representative references related to benzylic\nC–H oxidation thus expanded the discussion in the revised manuscript Figure 6c\naccordingly.\nC6: The current analysis of catalyst performance lacks key characterization that directly\nreveals the mechanistic role of the Ni element in active site formation. It is recommended\nto supplement the study with in situ Raman spectroscopy measurements of Ni-WOC and\nWOC. This will explicitly clarify the regulatory role of Ni introduction on the catalyst's\nsurface electronic structure, active species formation, and reaction pathway, thereby\nproviding direct spectroscopic evidence.\nR6: We conducted in-situ Raman spectra analysis according to the reviewer’s kind\nsuggestion to confirm the electrode phase change (Figure S11) but failed to get possible\nmolecular details of the reaction pathway due to resolution limitations under reaction\nconditions. We then turned to the potentiodynamic ATR-SEIRAS technique, which is more\nsuitable for polarized molecules and successfully provided clear molecular-level insights\ninto the role of Ni heteroatoms in the active species formation and reaction pathway.\nThe ATR-SEIRAS results indicate the facile water adsorption (Figure 5e) and C–H activation\nby forming W–O–C intermediate (Figure 5g) on Ni-WOC-based electrode. In sharp\ncontrast, both water adsorption (Figure 5e) and W–O–C formation (Figure 5g) on WOC-\nbased electrode are undetectable. Theoretically, the DFT calculation results further reveals\nthe key role of Ni dopant in modulates the electronic deficiency of neighboring W sites\n(Figure S20-21 in the revised supplementary information), resulting in a higher d-band\ncenter (Figure S20 in the revised supplementary information) for more favorable water\nadsorption (Figure 5a), *O species formation (Figure 5k) and final C–H activation via the\nformation of W–O–C intermediates (Figure 5k). We added all these results as Figure S11,\nFigure 5, and Figure S20-21 of the revised version and gave a clear description regarding\nthe detailed active species formation and the reaction pathway in the main text to clarify\nthe reviewer’s concerns.\nWe thank the reviewer’s recognition of the achievements and novelty of our work. And we\nhighly appreciate the reviewer’s kind suggestions and efforts to make our work better.\nReviewer #2:\nThe manuscript reports an oxygen transfer process boosted by operando evolved “Ni-\nactivated tungsten-oxygen covalency”. This work achieves an impressive Faradaic\nefficiency up to 56% along with near-unity regioselectivity for the oxygenation of benzylic\nC(sp3)–H bonds under the additive-free and water-containing conditions. I appreciate the\nauthors’ comprehensive investigation into the catalyst structure evolution, water structure\nregulation, and the entire oxygen transfer path using extensive in-situ and ex-situ\nspectroscopic techniques. The authors have clarified the whole oxygen transfer process\nwith several isotope-labeling and parallel in-situ spectroscopic experiments, providing\nvaluable insights for further related works. Thus, I would like to recommend this interesting\nwork for publication at Nature Communications after addressing the following concerns.\nC1: Though the depressed OER performance is manifested by the increased Faradaic\nefficiency of the C–H oxygenation process, a direct quantification of oxygen gas evolution\nis still necessary to validate this result.\nR1: We thank the reviewer’s thoughtful suggestion. To analyze the oxygen evolution\nquantitively, we collected and analyzed the produced gas in a 2-hour standard reaction.\nThe Faradaic efficiency of oxygen evolution (Figure S29 in the revised supplementary\ninformation) on Ni-WOC-based electrode is calculated to be 34.1%, significantly lower than\nthe Faradaic efficiency of 55.2% on WOC-based electrode. This result is consistent with\nthe increased Faradaic efficiency (57.5 % on Ni-WOC electrode vs. 37.2 % on WOC\nelectrode) of C–H oxidation and higher energy barrier (3.33 eV on Ni-WOC model vs. 3.02\neV on WOC model) of rate determining OER step from *O to *OOH. All these results are\nadded as Figure S29 in the revised supplementary information and briefly discussed in the\nrevised main text.\nC2: The XPS data in Figure 3d-f are crucial for tracking the catalyst reconstruction. For\nclarity, it would be beneficial to explicitly state the atomic ratios (e.g., W6+/W0, Ni2+/Ni0,\nlattice/adsorbed oxygen) in the main text or a supplementary table at each time point to\nquantitatively support the description of the oxygen migration process.\nR2: Expert comments. To quantitively reveal the structural reconfiguration process of the\npre-catalyst, we have calculated the atomic ratios of lattice oxygen-to-adsorbed hydroxyl\noxygen, Ni2+/Ni0, and W6+/W0. the lattice oxygen-to-adsorbed hydroxyl oxygen ratio\nincreased from 0.26 to 0.69, the Ni2+/Ni0 ratio rose from 0.15 to 9.80, and the W6+/W0 ratio\nincreased from 0.37 to 20.88 (Table S3 in the revised supplementary information) from 0\nmin to 30 min during reaction process, respectively. We have added these results as Table\nS3 in the revised supplementary information.\nC3: The electrochemical surface area (ECSA) is important for ruling out morphological\ncontributions to the enhanced catalytic performance. The authors should provide full\nexperimental details of the ECSA measurements, including the electrolyte composition and\npotential scan range.\nR3: We thank the reviewer for this kind suggestion. We have incorporated detailed\nexperiments procedures in the revised supplementary information.\nC4: The assignment of the active oxygen species as adsorbed oxygen (*O) is supported\nby both experimental and theoretical evidence. This finding aligns with several recent\nreports (e.g., J. Am. Chem. Soc. 2025, 147, 26254–26266; Nat. Rev. Chem. 2024, 8, 277–\n293), and citing these works would help strengthen the mechanistic claims.\nR4: We thank the reviewer for the kind suggestion. We have cited these articles in the\nrevised main text properly.\nC5: The absence of deuterated products in D O isotope-labeling experiments suggests\n2\nthat *OH or *OOH species are not directly involved in oxygen transfer. While this may hold\nfor alcohol formation, the pathway to acetophenone could involve dehydration of peroxidic\nintermediates. Though, as a minor product, the ketone formation pathway is still important\nfor strengthening the mechanistic discussion.\nR5: We thank the reviewer for the insightful comment. To identify the mechanism of ketone\nformation, we used cumene as a substrate to trap potential reactive oxygen species. The\ndetection of cumyl hydroperoxide in the products (Figure S35 in the revised supplementary\ninformation) indicates that ketone formation proceeds via the dehydration of hydroperoxide\nintermediates, representing a distinct pathway from the major alcohol-forming route. These\nresults have been incorporated into the revised supplementary information as Figure S35,\nand we have provided a clear description of the product distribution and underlying\nmechanisms in the revised supplementary information Figure S7.\nMinor concerns:\nC1: The inset of Figure 2b is mentioned but not clearly labeled in the caption. Please\nspecify what the inset shows.\nR1: We thank the reviewer for the careful reading. We have added the description of the\ninset picture of Figure 2b in the figure caption text.\nC2: Please ensure all abbreviations are defined upon first use (e.g., DRT is defined in the\ncaption of Figure 4 but should also be defined when first mentioned in the main text).\nR2: We thank the Reviewer for the careful reading. We have thoroughly checked the main\ntext and revised these oversights.\nWe are grateful for the review’s recognition of the importance and novelty of our work.\nAdditionally, we deeply value the reviewer's constructive suggestions and efforts in\nrefining our paper.\nReviewer #3:\nIn this manuscript, the authors report a Ni-WOC catalyst generated by the in-situ\nelectrochemical oxidation of a Ni–W C pre-catalyst, which exhibits high efficiency for the\n2\noxidation of benzylic C(sp3)–H bonds into the corresponding alcohols and ketones. Based\non combined experimental and theoretical results, the authors propose that Ni doping\nsignificantly weakens the interfacial hydrogen-bond network of water, facilitates water\nadsorption and dissociation on W sites adjacent to Ni to form active *O species, and thus\nsuppresses the OER pathway while promoting C–H bond oxidation of the organic substrate.\nThe discovery that Ni doping modulates the interfacial water structure and reaction\npathway is indeed interesting and potentially important. However, several key mechanistic\naspects remain insufficiently clarified and merit further explanation.\nC1: The manuscript does not provide sufficient structural evidence for the Ni-WOC catalyst.\nHow is the coordination environment of Ni and W confirmed? Is Ni atomically dispersed\nwithin the WOC structure? Without clear structural information, the theoretical models\nadopted in this work lack credibility, and consequently, the derived mechanistic conclusions\nare questionable. Admittedly, obtaining precise structural information for the Ni-WOC\ncatalyst is extremely challenging, as it is in-situ generated during electrolysis and is\namorphous in nature. Nevertheless, at least indirect structural evidence (e.g., XAS, EXAFS,\nor HAADF-STEM) is expected to support the proposed Ni–O–W configuration.\nR1: We initially conducted EXAFS measurement according to the reviewer’s expert\nsuggestion but failed to get a convincing result on the detailed coordination environment\nof Ni atoms (Figure R1) principally due to the rather low Ni content (1.6 wt.% via ICP-OES,\nTable S1). Nevertheless, the proposed Ni-WOC model can be confirmed by the XPS\nspectra of Ni-WOC catalysts with significant emergence of Ni2+ and W6+ (Figure 3g-h) and\nabundant lattice oxygen (Figure 3f). And both in-situ and ex-situ Raman spectra (Figure\nS11) reveal the presence of tungsten oxides as majority of the Ni-WOC sample mainly in\nthe form of amorphous phase according to the XRD analysis results (Figure S10).\nThe homogeneous distribution of Ni2+ over amorphous oxide clusters has now also been well\ndemonstrated by the atomic-resolved AC-HAADF-STEM image (Figure 3c-d of the revised\nmain text) of the reconstructed Ni-WOC sample, which directly shows the replacement of\nW to Ni atoms with obvious contrast difference in amorphous oxide clusters and the\ncomparable Ni/W–W distance. More importantly, ICP-OES results (Table S8 of the revised\nsupplementary information) reveal comparable Ni/W atomic ratios of 0.086 for Ni-WOC\nsample and 0.095 for the pre-catalyst Ni-W C sample, rather suggesting the well-\n2\nmaintained Ni contents and the co-existence of Ni and W sites during the reconstruction\nprocess and long-term uses for 48 h. Collectively, considering the co-existence of Ni and\nW atoms in these amorphous clusters and the emergence of lattice oxygen, we proposed\na Ni doped tungsten oxide model, which is used for further theoretical investigation after\nstructural optimization. We have added new results above as Figure 5c-d and Table S8 in\nthe revised version and fully discussed them in the revised main text.\nFigure R1. The EXAFS analysis of used Ni doped sample. (a) EXAFS spectra of used\ncatalysts. (b) Furrier transformed EXAFS oscillation from 0 to 6 Å of used catalysts.\n(c) k3-Weighted EXAFS oscillation of used catalysts.\nC2: The manuscript lacks a clear explanation of the design logic behind the Ni-WOC\nsystem. Why was Ni-doped W C chosen as the catalyst precursor? What is the rationale\n2\nfor combining Ni and W? Why not directly prepare a Ni-doped metal oxide catalyst instead\nof starting from a carbide precursor? A discussion of the design concept and motivation\nwould significantly strengthen the work.\nR2: Insightful comments. As a well-known heterogeneous catalyst for C–H activation, WO\n3\nusually suffers from low dispersion with a limited amount of exposable active cites.\nEngineering the amorphous phase and introducing active heteroatoms are straightforward\nmethods to largely promote the activity of WO -based nano-catalysts by improving the\n3\ndispersion and modulating the electronic structure, respectively. Unfortunately, the direct\ndeposition of WO on various carbon supports could only give large aggregates, rather\n3\nspeaking for the key importance of our reconstruction method to prepare highly dispersed\nand amorphous WO clusters with better catalytic performance than crystalline WO\n3 3\n(Figure 3i) even without the introduced Ni dopants.\nAmong the possible candidates of dopants including Fe, Co, Ni, and Mn, et al., Ni atoms\nexhibit favorable lattice matching with both W C and WO to keep from obvious leaching\n2 3\nduring the specific in-situ reconstruction process in this work, as well reflected by our ICP-\nOES and EDS analysis results (Table S8). The synergy between the Ni dopants and as-\nformed WOC sites can largely disrupt the interfacial hydrogen bond network and\nsimultaneously boost the co-activation of water molecules and C–H bonds, which is the\nkey point of this work to well reflect our design concept and motivation. We have added all\nthese results and detailed discussion in introduction part and Page 8 Paragraph 2 in the\nrevised main text according to the reviewer’s kind suggestions to elucidate the essential\nrole of reconstruction process and the doping of Ni atoms.\nC3: Does the oxidation state of Ni in Ni-WOC change after catalysis? The manuscript does\nnot present post-reaction or recycled catalyst characterizations. Could Ni be oxidized to\nNi3+ during operation? Such information is crucial to understanding the stability and real\nactive state of the catalyst.\nR3: Thoughtful comments. We further provided comprehensive characterization of the Ni-\nWOC sample after a 48-hour electrolysis. EDS mapping (Figure S31e-f in the revised\nsupplementary information) confirms the homogeneous distribution of Ni atoms over the\nwhole support of the spent catalyst. Quantitative EDS spectra (Figure S31d and Table S8\nin the revised supplementary information) and the ICP-OES (Table S8) analysis results\ndemonstrate the consistent Ni/W atomic ratios before (0.095 via ICP-OES) and after (0.086\nvia ICP-OES and 0.107 via EDS) long-term uses. XPS results of the spent Ni-WOC catalyst\n(Figure S33a-b) further reveal the existence of Ni2+ at around 856.4 eV. All these results\nindicate the well maintained Ni2+ oxidation state and content after a 48-hour electrolysis.\nThe unsatisfactory electrocatalytic performance using Ni/NC or WOC alone as catalysts\n(Figure 3i) further demonstrate the key role of the Ni-WOC complex, rather than Ni atoms\nnor bare WOC sites, as the synergistic active centers to promote effective oxygen transfer\nfrom water to C–H bonds. We added all these results as Figure S31, Figure S33, and Table\nS8 to clarify the reviewer’s concern on the stability and real active state of the catalyst.\nC4: The results suggest that the truly active site is the W center adjacent to Ni. Please\nprovide a molecular-level explanation of how Ni modulates the Ni–O–W interface. Could\nother transition metals play a similar role? A comparative discussion would make the\nmechanistic proposal more convincing.\nR4: We thank the reviewer for this constructive suggestion. To gain deeper insight into how\nNi heteroatoms modulate the W–O covalency quantitively, we investigated the electronic\nstructure of the Ni-WOC model and WOC model, respectively. The partial density of states\nreveals an upward shift in the d-band center of metal sites (Figure S20) from –1.959 eV\n(WOC) to –1.902 eV (Ni-WOC). The Bader charge (Figure S21a-c) and differential charge\ndensity (Figure S21d) analysis results further demonstrate the role of Ni heteroatom as\nelectron acceptor to attract 0.22 e– from the adjacent WOC site (W1 in Figure 5a and Figure\nS21). The as-formed electron-deficient W1 site benefits following water adsorption and\nsubsequent C–H activation via W–O–C intermediate formation. Principally, other transition\nmetals (e.g. Fe, Co, Mo) may play a similar role. However, considering the carbides\nreconfiguration strategy, we choose Ni as the dopant in this research. All these results have\nbeen added as Figure S20-21 in the revised supplementary information and fully discussed\nin the revised main text to elucidate the role of Ni in the electronic structure modulation.\nC5: The proposed oxidation pathway of ethylbenzene is not clearly explained. According\nto the current DFT results, the substrate is adsorbed at the W site adjacent to Ni, loses an\nelectron, undergoes benzylic C–H bond homolysis to form *C H , which is then oxidized\n8 9\nby *O to *C H O, and finally gains a hydrogen to form the alcohol product.\n8 9\nMy question is: Where does this final hydrogen come from? If it originates from solvent\nwater, why were no D O-labeled products detected in isotope-labeling experiments? If not\n2\nfrom water, what is the hydrogen source? Please provide evidence or additional discussion.\nR5: Expert comments. We performed DFT calculations comparing the proton-coupled\nelectron transfer (PCET) and hydrogen atom transfer (HAT) pathways (Figure S27 and\nTable S6 in the revised supplementary information). The results show that the HAT pathway,\nforming *C H and *H with a barrier of 0.81 eV, is more favorable than the PCET pathway\n8 9\n(with a barrier of 0.94 eV) which forms *C H , H+ and e– (Figure S27 and Table S6 in the\n8 9\nrevised supplementary information). Following HAT pathway for C–H activation, the\nadsorbed *H participate in the final formation of the alcohol (Figure S27 and Table S6 in the\nrevised supplementary information). This theoretical preference for HAT is consistent\nwith our isotope-labeling experiments, in which no deuterated products were detected.\nBoth the experimental and theoretical results support the proposed HAT pathway for the\nC–H activation process. We have added these results as Figure S27 and Table S6 to the\nrevised supplementary information. The manuscript Figure 5k was also modified to clarify\nthe DFT calculation regarding the C–H activation process.\nC6: The oxidation process involves multiple steps, including water oxidation to *O,\nethylbenzene oxidation to *C H O, and further oxidation of *C H O by *O. Which step is\n8 9 8 9\nrate-determining? What are the kinetic isotope effect (KIE) values for these steps?\nKinetic analysis is essential to support the proposed mechanism.\nR6: According to the reviewer’s constructive suggestion, we measured the polarization\ncurves for both the OER and the combined OER/ethylbenzene oxidation reaction in H O-\n2\nand D O-based electrolytes (Figure S30b-d in the revised manuscript). Upon adding\n2\nethylbenzene, a new oxidation peak emerged at 1.72 V (vs. Ag/AgCl), corresponding to\nethylbenzene oxidation. The calculated kinetic isotope effect (KIE) value ( 𝑗 /𝑗 ) at 1.72 V\nH D\n(𝑗 : the current density measured in H O-based electrolyte, and 𝑗 : the current density\nH 2 D\nmeasured in D O-based electrolyte) decreases from 1.40 (OER alone) to 1.22 (with\n2\nethylbenzene), indicating that the isotopic effect of water oxidation becomes less dominant\nwhen C–H activation and oxidation are involved. This experimental trend aligns well with\nour theoretical calculation results (Figure 5k), that is, the co-activation of absorbed\nethylbenzene and as-formed *O from water oxidation as the rate-determining step with an\nenergy barrier of 2.83 eV. We have added these results to the revised supplementary\ninformation as Figure S30b-d and fully discussed them in the revised main text.\nC7: The regioselectivity mentioned in the manuscript is not appropriate. The preferential\noxidation at the benzylic C–H position results from its inherently higher reactivity, rather\nthan a catalyst-induced regioselective effect. This term should be revised or clarified.\nR7: We thank the reviewer for this thoughtful comment. We conducted electrochemical\nexperiments using cyclohexane without detectable oxidation products, validating the\nreviewer’s prediction that the observed regioselectivity is indeed attributable to the intrinsic\nactivity of the benzylic C–H bond itself. We have added detailed discussion on this point to\nPage 16 Line 366-369 of the revised main text to clarify this concern.\nC8: The reaction yields both alcohol and ketone products, and the ketone is likely derived\nfrom further oxidation of the alcohol. Since two products are obtained simultaneously rather\nthan one dominant product, the description of a “selective oxygenation process” is not\naccurate.\nR8: We agree with the reviewer’s suggestion and lower down the tune of the selective\nprocess to effective activation of C–H in the revised version.\nC9: In the conclusion, the statement “Ni heteroatoms disrupt the water structure …\nfacilitating the rapid diffusion of oxygen species to the W–O covalency sites of Ni-WOC” is\nunclear. What exactly does “oxygen species” refer to — water molecules, *O, or other\nintermediates? This should be explicitly defined.\nR9: According to the reviewer’s kind suggestion, we replaced the “oxygen species” to\n“water molecules” in the revised version.\nFinally, we express our gratitude for the reviewer's recognition of the importance of our\nwork. We are also deeply appreciative of the valuable and constructive suggestions and\nefforts that have contributed to refining our paper."}, {"round": 2, "reviewer_comments": {"reviewer_1": "The work is significant to the field and related fields. The work support the conclusions and claims. The methodology is sound and meet the expected standards.", "reviewer_2": "The authors provide a suitable response and revision to my concerns. Thus, this manuscript can be accepted at its present version.", "reviewer_3": "The authors have carefully addressed the majority of my previous comments and provided reasonable explanations and additional analyses where appropriate. Although clear structural information of the Ni–WOC catalyst is still not fully resolved, the revised manuscript presents convincing evidence for the high dispersion of Ni species, which sufficiently supports the authors’ key conclusions. Overall, the revisions have significantly improved the clarity, rigor, and quality of the manuscript. I therefore consider the manuscript suitable for publication in Nature Communications."}, "author_response": "Responses (R) to Comments (C)\nReviewer #1:\nC: The work is significant to the field and related fields. The work support the conclusions\nand claims. The methodology is sound and meet the expected standards.\nR: We express our gratitude for the reviewer's recognition of the importance of our work.\nAnd we are grateful for the efforts made by the reviewer in refining our manuscript.\nReviewer #2:\nC: The authors provide a suitable response and revision to my concerns. Thus, this\nmanuscript can be accepted at its present version.\nR: We are grateful for the review’s kind suggestions and efforts in refining our paper.\nReviewer #3:\nC: The authors have carefully addressed the majority of my previous comments and\nprovided reasonable explanations and additional analyses where appropriate. Although\nclear structural information of the Ni–WOC catalyst is still not fully resolved, the revised\nmanuscript presents convincing evidence for the high dispersion of Ni species, which\nsufficiently supports the authors’ key conclusions. Overall, the revisions have significantly\nimproved the clarity, rigor, and quality of the manuscript. I therefore consider the manuscript\nsuitable for publication in Nature Communications.\nR: We highly appreciate the reviewer’s previous constructive suggestions and efforts to\nmake our work better."}]

Decision letter