Two-electron Oxidation Of Water Research Articles

"B" site-modulated perovskite oxide materials for efficient electrochemical water oxidation to hydrogen peroxide

Two-electron water oxidation (2e− WOR) has emerged as a promising method for H2O2 synthesis. However, achieving catalyst’ stability for hydrogen peroxide (H2O2) production through 2e− WOR under harsh oxidative conditions remains a significant challenge. Perovskite oxide catalysts have shown potential at low currents, but their electrocatalytic activity diminishes at high current densities. In this study, we successfully fabricated highly efficient 2e− WOR electrocatalysts by carefully selecting suitable B site metals with optimal O* and OH* adsorption characteristics. Our results demonstrate that the LaCoO3 catalyst exhibit exceptional H2O2 production rates, reaching 2977.29 μmol min−1 g−1. Furthermore, the LaCoO3 catalysts demonstrate remarkable durability and stable electrochemical performance even after an ultra-long 120-hour stability test. Density Functional Theory calculations (DFT) further demonstrate that we successfully screened catalysts that are thermodynamically more favorable at a 2e− WOR pathway and accelerate the rate-determining step of OH* to H2O2 by B-site modulation. This work presents a simple and effective strategy for designing perovskite catalysts tailored for efficient 2e− WOR.

Effective electrochemical water oxidation to H2O2 based on a bimetallic Fe/Co metal–organic framework

A bimetallic Fe/Co metal–organic framework exhibits high-efficiency catalysis for electrochemical two-electron water oxidation reaction to produce hydrogen peroxide.

(Invited) Metal Oxide Mixed Sulphide of Controlled Crystal Structure As Catalysts for Two-Electron Water Oxidation

Conventional catalysts based on noble metals (Pt, Ru) are often used for production of oxygen during water electrolysis in four-electron pathway as they can decrease gas evolution overpotential. Another possible valuable product from water oxidation is hydrogen peroxide obtained via two-electron process. Currently, transition metal oxides, are readily employed to catalyse this reaction. Although they display certain activity, it is still not satisfactory for mass production of H2O2, therefore further optimisations are needed. We suggest in this work, in addition to typical nanostructure modifications of metal oxides (MoO2) such as doping or structural engineering, an application of transition metal dichalcogenides (MoS2). Consequently, the oxide is partially replaced by sulphur. The selection of molybdenum as a centre atom ensures sufficient electrical conductivity of material as an electrode active layer. This combination is intended to provide the benefits thanks to layered materials of tuned interlayer spacing as well as controlled number of active sites. It enables selective adsorption of intermediate products of water oxidation (O∗, OH∗, and OOH∗), and therefore increased preference towards two-electron pathway.Various chemical approaches are considered to synthesize this material, especially hydrothermal treatment in autoclave and high-temperature sintering of precursors. The catalytic activity of the nanostructured metal oxide is further enhanced by its deposition on conductive high surface area support made of carbon/graphite particles of strictly defined textural parameters and surface chemistry. The final composite is obtained using hydrophobic binders (PVDF and PTFE) to form the electrode and improve the catalyst stability. The measurements are carried out in flow electrolyser unit with an alkaline electrolyte. The amount of produced H2O2, H2 as well as quantity and quality of evolved gases are assessed in terms of faradaic efficiency, pressure and overvoltage measurements.

The Nexus of Innovation: Electrochemically Synthesizing H2O2 and Its Integration with Downstream Reactions.

Hydrogen peroxide (H2O2) represents a chemically significant oxidant that is prized for its diverse applicability across various industrial domains. Recent innovations have shed light on the electrosynthesis of H2O2 through two-electron oxygen reduction reactions (2e- ORR) or two-electron water oxidation reactions (2e- WOR), processes that underscore the attractive possibility for the on-site production of this indispensable oxidizing agent. However, the translation of these methods into practical utilization within chemical manufacturing industries remains an aspiration rather than a realized goal. This Perspective intends to furnish a comprehensive overview of the latest advancements in the domain of coupled chemical reactions with H2O2, critically examining emergent strategies that may pave the way for the development of new reaction pathways. These pathways could enable applications that hinge on the availability and reactivity of H2O2, including, but not limited to the chemical synthesis coupled with H2O2 and waste water treatment byFenton-like reactions. Concurrently, the Perspective acknowledges and elucidates some of the salient challenges and opportunities inherent in the coupling of electrochemically generated H2O2, thereby providing a scholarly analysis that might guide future research.

Flower-like WO2@C prepared from the pyrolyzation of ionic liquid for effective elctrocatalytic two-electron water oxidation

Flower-like tungsten dioxide@carbon (WO2@C) is prepared through the pyrolysis of 1-octyl-3-methylimidazolium tungstate ionic liquids. The resultant WO2 particles are surrounded by a few of carbon fibers, displaying the unique flower-like morphology. The WO2@C testified efficient electrocatalytic activity for two-electron water oxidation reaction (2e- WOR) to H2O2. The electrocatalytic H2O2 production rate reaches about 6.55 μmol min−1 cm−2, over 2 times higher than WO2. This may be ascribed to the enhanced electron transferring capacities and abundant defects of WO2@C. This work introduces a special ionic liquid-derived metal oxide@C with the improved electrocatalytic activity for 2e- WOR.

Tuning the Selectivity and Activity of Graphite for the Two-Electron Water Oxidation Reaction via Doping with Heteroatoms: A Density Functional Theory Study

Tuning the Selectivity and Activity of Graphite for the Two-Electron Water Oxidation Reaction via Doping with Heteroatoms: A Density Functional Theory Study

Photocatalytic degradation of chlorinated organic pollutants by ZnS@ZIF-8 composite through hydrogen peroxide generation by activating dioxygen under simulated sunlight irradiation

Photocatalytic hydrogen peroxide (H2O2) production and its application in advanced oxidation processes (AOPs) are regarded as low-cost and environmentally friendly wastewater treatment processes. Herein, by modifying a small amount of sulphide on the zeolitic imidazolate framework-8 (ZIF-8), a ZnS@ZIF-8 composite and used for photocatalytic H2O2 production to degrade chlorinated organic pollutants under simulated sunlight (SSL). ZnS@ZIF-8 composite could enhance the separation of photo-induced charge carriers, promote electron transfer from zinc sulphide (ZnS) to ZIF-8, which exhibited good selectivity for the two-electron oxygen reduction reaction (2e--ORR) and two-electron water oxidation (2e--WOR) pathways. Based on oxygen (O2) activation, the developed ZnS@ZIF-8/O2/SSL system could achieve 6.43 mmol/L H2O2 production within 150 min, which was approximately 8.66 and 10.36 times higher than that of the ZnS/O2/SSL and ZIF-8/O2/SSL systems, respectively. In the ZnS@ZIF-8/O2/SSL system, the ORR, WOR and H2O2 photolysis led to the generation of hydroxyl radical (•OH), while the photochemical behavior of ZnS in ZnS@ZIF-8 composite resulted in the generation of active hydrogen (*H). Benefitting from the high concentration of H2O2 and the coexistence of redox species in the ZnS@ZIF-8/O2/SSL system, various chlorinated organic pollutants could be dechlorinated and mineralized. In addition, a possible mechanism for photocatalytic H2O2 production was also proposed. Importantly, the proposed process did not involve an additional sacrificial agent or Fenton-like catalysts. This work provides insights into the potential application of ZnS@ZIF-8 composite for H2O2 production and wastewater treatment.

A general strategy to enhance hydrogen peroxide generation via two-electron water oxidation by antimony modification for removal of triethyl phosphate and hexavalent chromium

Two-electron water oxidation has attracted more and more attention for H2O2 production. This strategy mainly uses water and does not require bubbling of oxygen gas, which can be widely used in oxygen-deficient environments. Currently, the most important research for two-electron water oxidation is the design of high-efficiency anode materials. Herein, a general method is developed to enhance the activity of two-electron water oxidation for H2O2 production via Sb2O3 modification. This strategy is suitable for a series of electrodes, including carbon fiber paper, graphite plate, WO3, CuWO4 and WO3&CuWO4 composite. The mechanism for Sb2O3 modification toward enhanced H2O2 generation is clearly demonstrated. It should be due to three factors: 1) enhance the reaction kinetic, 2) enlarge the specific surface area and 3) suppress H2O2 decomposition. According to density function calculation, it is firstly found that the Sb optimizes the Gibbs free energy of adsorbed *OH intermediate of its nearby atom, making its adjacent atom (such as W) the active site. Finally, these Sb-modified electrodes are firstly used to produce H2O2 for high-efficiency removal of triethyl phosphate, an environmental pollutant that are difficult to be degraded. It can also be used for the removal of hexavalent chromium, one kind of heavy metal.

Super-Oxidizing Covalent Triazine Framework Electrocatalyst for Two-Electron Water Oxidation to H2O2.

Electrochemical two-electron water oxidation (2e WOR) is gaining surging research traction for sustainable hydrogen peroxide production. However, the strong oxidizing environment and thermodynamically competitive side-reaction (4e WOR) posit as thresholds for the 2e WOR. We herein report a custom-crafted covalent triazine network possessing strong oxidizing properties as a proof-of-concept metal-free functional organic network electrocatalyst for catalyzing 2e WOR. As the first-of-its-kind, the material shows a maximum of 89.9% Faradaic Efficiency and 1428 μmol/h/cm2 H2O2 production rate at 3.0 V bias potential (vs reversible hydrogen electrode, RHE), which are either better or comparable to the state-of-the-art electrocatalysts. We have experimentally confirmed a stepwise 2e WOR mechanism which was further computationally endorsed by density functional theory studies.

Coordination engineering regulating metal single-atom anchored on n-doped carbon as a bifunctional catalyst for H2O2 production via dual channels

Electrochemical synthesis of hydrogen peroxide (H2O2) via two-electron oxygen reduction reaction (2e- ORR) or two-electron water oxidation reaction (2e- WOR), parades great prospects in substituting traditional anthraquinone process. However, the low efficiency and selectivity hinders its practical utilization. Exploration of a bifunctional catalyst capable of simultaneously driving the 2e- WOR and 2e- ORR is crucial for thoroughly improving H2O2 conversion efficiency. Herein, by means of first principles calculation, the 2e- ORR and 2e- WOR activities of metal-nitrogen doped carbon (M−NC, M = Mn, Fe, Co, Ni, Ru, In, and Pt) are investigated. Combining the pyrrole nitrogen coordination regulation, the best sample (RuN(Po)4) is screened from forty single atom configurations, which exhibits ultra-low overpotentials (0.02 V/0.04 V) and excellent inhibition on 4e- ORR/WOR side reactions. In-depth study further verifies its low reaction energy barrier and high thermodynamic stability for H2O2 synthesis in two pathways. Our work is expected to provide useful understanding for designing highly-efficient bifunctional catalysts for H2O2 production.

Prospects and Promises in Two-Electron Water Oxidation for Hydrogen Peroxide Generation

Prospects and Promises in Two-Electron Water Oxidation for Hydrogen Peroxide Generation

Embedding Carbon Quantum Dots into Crystalline Polyimide Covalent Organic Frameworks to Enhance Water Oxidation for Achieving Dual-Channel Photocatalytic H2O2 Generation in a Wide pH Range.

Photocatalytic technique is regarded as the cleanest approach for producing H2O2. Herein, two kinds of novel polyimide COFs decorated with CQDs (namely, MPa-COFs/CQDs and MNd-COFs/CQDs) were constructed by using the one-pot hydrothermal method. Due to the electron donor role of CQDs, the recombination of photoinduced electrons and holes was suppressed after the combination of polyimide COFs with CQDs. Importantly, the introduction of CQDs not only boosted the absorbing ability of polyimide COFs toward visible light but also reduced the impedance and improved the charge transfer efficiency. After CQDs were embedded into polyimide COFs, the surface hydrophilicity of catalysts was significantly improved, which provided convenience for the water oxidation reaction. Benefiting from the electron donor-acceptor interaction between polyimide COFs and CQDs, a step-by-step two-electron oxygen reduction reaction over polyimide COFs was enhanced. More interestingly, the embedding of CQDs can create a direct two-electron water oxidation reaction pathway, which played an important role in photocatalytic H2O2 generation. Meanwhile, H+ generated from water oxidation can also be used for the reduction of oxygen to form H2O2. Under the synergistic effects of water oxidation and oxygen reduction, as-prepared MPa-COFs/CQDs-2 displayed excellent performance in photocatalytic H2O2 generation, and its yield was as high as 540 μmol/g within 60 min. In short, the current work shared an effective strategy to improve the performance of polyimide COFs in photocatalytic H2O2 production.

Rational Design of Conjugated Acetylenic Polymers Enables a Two-Electron Water Oxidation Pathway for Enhanced Photosynthetic Hydrogen Peroxide Generation.

Herein, the design of conjugated acetylenic polymers (CAPs) featuring diverse spatial arrangements and intramolecular spacers of diacetylene moieties (─C≡C─C≡C─) for photocatalytic hydrogen peroxide (H2 O2 ) production from water and O2 , without the need for sacrificial agents, is presented. It is shown that the linear configuration of diacetylene moieties within conjugated acetylenic polymers (CAPs) induces a pronounced polarization of electron distribution, which imparts enhanced charge-carrier mobility when compared to CAPs' networks featuring cross-linked arrangements. Moreover, optimizing the intramolecular spacer between diacetylene moieties within the linear structure leads to the exceptional modulation of the band structures, specifically resulting in a downshifted valence band (VB) and rendering the two-electron water oxidation pathway thermodynamically feasible for H2 O2 production. Consequently, the optimized CAPs with a linear configuration (LCAP-2), featuring spatially separated reduction centers (benzene rings) and oxidation centers (diacetylene moieties), exhibit a remarkable H2 O2 yield rate of 920.1µmol g-1 h-1 , superior than that of the linear LCAP-1 (593.2µmol g-1 h-1 ) and the cross-linked CCAP (433.4µmol g-1 h-1 ). The apparent quantum efficiency (AQE) and solar-to-chemical energy conversion (SCC) efficiency of LCAP-2 are calculated to be 9.1% (λ = 420nm) and 0.59%, respectively, surpassing the performance of most previously reported conjugated polymers.

Microstructural Origin of Selective Water Oxidation to Hydrogen Peroxide at Low Overpotentials: A Study on Mn-Alloyed TiO2

Introduction: Hydrogen Peroxide, H2O2, is a versatile chemical with applications ranging from industrial to household use such as pulp bleaching, wastewater treatment, and sterilization. In addition to these established uses, H2O2 is emerging as a green energy carrier which can release 96 kJ mol−1 of energy via exothermic chemical decomposition with only water and oxygen as by-products. Currently, more than 95% of H2O2 produced globally originates from anthraquinone autoxidation. This process requires precious metal catalysts and expensive liquid-liquid extraction processes that are only feasible for large-scale chemical plants.Electrochemical and photochemical syntheses are promising alternatives for distributed H2O2 production. H2O2 can be produced by 2e- processes both via oxidatively, via water oxidation reaction (WOR) or reductively via oxygen reduction reaction (ORR). These approaches take advantage of abundant energy sources, i.e., renewable electrical or solar energy, and enables the storage of intermittent energy as the free energy of chemical bonds for distributed energy storage. Charge Transfer: H2O2 can be (photo-)electrochemically synthesized via a two-electron (2e−) water oxidation pathway, as shown in equation 1.2H2O → H2O2 + 2H+ + 2e−, E = +1.77 VRHE (1)However, existing catalysts often exhibit low faradaic efficiency (FE) due to the competitive four-electron (4e−) pathway of O2 evolution reaction (OER) equation 2.2H2O → O2 + 4H+ + 4e−, E = +1.23 VRHE (2)The thermodynamic driving force for OER is always at least +0.54 V greater than that of the 2e− H2O2 pathway which can allow the undesired O2 evolution pathway to overcome any kinetic barriers and dominate. In addition, the produced H2O2 can be over-oxidized to O2 at an excess potential of at least +1.09 V equation 3.H2O2 → O2 + 2H+ + 2e−, E = +0.68 VRHE (3)Thus, the partial oxidation of water to hydrogen peroxide presents a model system of a common challenge in catalysis where the desired product is kinetically feasible but thermodynamically unfavorable.In this work, we utilize X-ray Photoelectron Spectroscopy to quantify the presence of Mn(III) defect states within the TiO2 band gap which are energetically aligned to peroxide generating reactive intermediates.During operation, the energy levels of CB and VB of TiO2 are fixed, or “pinned”, at −0.05 and 3.29 VRHE, respectively, yet the empty states of the Mn defect states can precisely align with the energetics of H2O2 producing intermediates. Under a higher applied potential, i.e., +2.3 VRHE, there would exist a moderate overpotential for the 2e− water oxidation, but such a potential also enables the other pathways including 1e− water oxidation to produce radicals, leading to an overall reduction in H2O2 production rates due to the reduced selectivity. Thus, this strategy of defect state tuning is best suited to low overpotentials, <100mV, catalysis. Conclusion: This study presents a new strategy of introducing charge-transport defect states and demonstrates the design of H2O2-producing surfaces that oxidize water to H2O2 with high selectivity at very low overpotentials. Given the growing literature related to H2O2 selective catalysis, this approach is expandable to a range of host oxides that prevent H2O2 disproportionation to favor 2e− H2O2 electrochemistry.Faradaic efficiency of >90% at < 150 mV overpotentials was achieved for H2O2 production, accumulating 2.97 mM H2O2 after 8 hours. Nanoscale mixing of Mn2O3 and TiO2 resulted in a partially filled, highly conductive Mn3+ intermediate band (IB) within the TiO2 mid-gap to transport charge across the (Ti,Mn)Ox coating. This IB energetically matched that of H2O2-producing surface intermediates, turning a wide bandgap oxide into a selective electrocatalyst capable of operating in the dark. Figure 1

A Molecular Z-Scheme Artificial Photosynthetic System Under the Bias-Free Condition for CO2 Reduction Coupled with Two-electron Water Oxidation: Photocatalytic Production of CO/HCOOH and H2 O2.

Bio-inspired molecular-engineered systems have been extensively investigated for the half-reactions of H2 O oxidation or CO2 reduction with sacrificial electron donors/acceptors. However, there has yet to be reported a device for dye-sensitized molecular photoanodes coupled with molecular photocathodes in an aqueous solution without the use of sacrificial reagents. Herein, we will report the integration of SnIV - or AlIII -tetrapyridylporphyrin (SnTPyP or AlTPyP) decorated tin oxide particles (SnTPyP/SnO2 or AlTPyP/SnO2 ) photoanode with the dye-sensitized molecular photocathode on nickel oxide particles containing [Ru(diimine)3 ]2+ as the light-harvesting unit and [Ru(diimine)(CO)2 Cl2 ] as the catalyst unit covalently connected and fixed within poly-pyrrole layer (RuCAT-RuC2 -PolyPyr-PRu/NiO). The simultaneous irradiation of the two photoelectrodes with visible light resulted in H2 O2 on the anode and CO, HCOOH, and H2 on the cathode with high Faradaic efficiencies in purely aqueous conditions without any applied bias is the first example of artificial photosynthesis with only two-electron redox reactions.

Phtotoelectrochemical water oxidation to H2O2 based on N-TiO2 derived from NH2-MIL-125 and in-situ application on degradation dye

Electrochemical two-electron water oxidation reaction (2e− WOR) to produce H2O2 has been widely concerned. However, four-electron competition reaction causes the large overpotential and low production rates of 2e− WOR, which restrict its’ development and application. Herein, we prepared N-TiO2 derived from NH2-MIL-125 by the hydrothermal combined with calcination method. We found that N-TiO2 as photoanode exhibited the well properties of photoelectrocatalysis water oxidation, which gave an overpotential of 630 mV at 1 mA cm−2. The overpotentials of N-TiO2 was approximately 130 mV (at 1 mA cm−2) lower than NH2-MIL-125, and even lower than the previous reported TiO2, which may attribute to the increased oxygen vacancy with the calcination process and N doping. In addition, we investigated the degradation performance of the prepared catalysts to degrade methylene blue by photoelctrocatalysis on-site the preparation of H2O2. It was shown that N-TiO2 performed high degradation efficiency (∼91%) and excellent stability. The possible mechanism was speculated due to the increased oxygen vacancy and N doping. This work provides a new idea for photoelectrocatalysis water oxidation materials and points out a new way for on-site H2O2 production for direct use.

The synergism of Co3O4 co-catalysis and Pt-doping boosting hematite photoanode for efficient solar H2O2 synthesis

Photoelectrochemical (PEC) syntheses is a green approach for the production of H2O2, which depends on the semiconductor photoanode to initiate the two-electron oxidation of H2O into H2O2. At present, the development of cheap and efficient photoanodes for H2O2 production holds great promise, but remains challenging. Herein, a Co3O4@Pt-Fe2O3 photoanode was designed and investigated for H2O2 production, based on the assistance of Co3O4 co-catalysis and Pt-doping. The Co3O4@Pt-Fe2O3 photoanode demonstrated superior PEC performance towards H2O2 production, a H2O2 production Faraday efficiency of 77.38% and a H2O2 yield of 0.073 μmol cm−2 be achieved at 1.00 V vs. RHE under AM 1.5 G irradiation. The experimental investigations and theoretical calculations jointly revealed the synergistic effect of Co3O4 co-catalysis and Pt-doping on the Co3O4@Pt-Fe2O3 photoanode for H2O2 production. Specifically, Pt-doping introduces defect sites into Fe2O3 photoanode, which could improve the bulk carrier mobility and density. Meanwhile, Co3O4 co-catalysis is conducive to achieve two-electron water oxidation on Pt-Fe2O3 photoanode selectively, and weaken the decomposition of H2O2 product in cell. Furthermore, the internal electric field of Co3O4/Pt-Fe2O3 can promote the separation of surface carrier for H2O2 production. The present work presents an efficient Co3O4@Pt-Fe2O3 photoanode for H2O2 production, which could inspire the development of similar materials for H2O2 synthesis.

ZnO/Co-doped polyhistidine as an efficient bioelctrocatalyst for hydroxyl radical generation: Fabrication, characterization and application for microbial inactivation

The hydroxyl radical (•OH) is a well-known powerful oxidizing agent that can react unselectively with the environmental contaminants. Electrochemical radical generation has been regarded as a promising choice to enable H2O2 formation and its converting to •OH. Here, by modifying of zinc oxide with cobalt doped polyhistidine (Co:pHis), we succeeded in fabricating a new, efficient, and stable bioelectrocatalyst for converting the two-electron water oxidation reaction (2e-WOR) product to •OH. The structural, morphological and electrochemical properties of fabricated bioelectrocatalyst were investigated by different characterization techniques. The functional groups of pHis increased the rate of 2e-WOR due to the formation of hydrogen bonding with H2O2. The presented bioelectrocatalyst gives an overpotential of 2.6 V (vs. RHE) at 0.2 mA/cm2 and peak Faradaic efficiency of 57% toward •OH generation. The electrogenerated •OH by the proposed new bioelectrocatalyst was successfully applied for the inactivation of E. coli (>95%) as a typical microbial contaminant.

Improved photocatalytic H2O2 production of boron doped g-C3N4 by controllably co-modifying nanosized PDI and Ag

Herein, boron-doped g-C3N4 (BCN) is first modified with perylene diimide (PDI) nanosheets driven by the π−π interactions, and subsequently decorated with nanosized Ag through the photodeposition method. The optimal PDI/BCN-Ag photocatalyst achieves a H2O2 production rate of 143 μmol g−1 h−1 without any sacrificial agents under visible light irradiation, which is about13-fold improvement compared with pristine g-C3N4. The boosted photoactivity is mainly ascribe to the enhanced charge separation due to the cascade S-scheme charge transfer between the coupled PDI and BCN, and the promoted oxygen activation from the introduced nanosized Ag by means of the time-resolved surface photovoltage responses and fluorescence spectra, kelvin probe measurement analyses, O2 temperature-programmed desorption and electron paramagnetic resonance spectroscopy. Notably, there is a dual channel for H2O2 production on PDI/BCN-Ag. The two-electron oxygen reduction dominated by the produced •O2− radicals occurs on the Ag nanoparticles, whereas the two-electron water oxidation occurs on the PDI.

Simultaneous Generation of H2 O2 and Formate by Co-Electrolysis of Water and CO2 over Bifunctional Zn/SnO2 Nanodots.

Hydrogen peroxide (H2 O2 ) and formate are important chemicals used in various chemical manufacturing industries. One promising approach for the simultaneous production of these chemicals is coupling anodic two-electron water oxidation with cathodic CO2 reduction in an electrolyzer using nonprecious bifunctional electrocatalysts. Herein, we report an innovative hybrid electrosynthesis strategy using Zn-doped SnO2 (Zn/SnO2 ) nanodots as bifunctional redox electrocatalysts to achieve Faradaic efficiencies of 80.6 % and 92.2 % for H2 O2 and formate coproduction, respectively, along with excellent stability for at least 60 h at a current density of ≈150 mA cm-2 . Through a combination of physicochemical characterizations, including operando attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), isotope labeling mass spectrometry (MS)/1 H NMR and quasi-in situ electron paramagnetic resonance (EPR), with density functional theory (DFT) calculations, we discovered that the Zn dopant facilitates the coupling of *OH intermediates to promote H2 O2 production and optimizes the adsorption of *OCHO intermediates to accelerate formate formation. Our findings offer new insights into designing more efficient bifunctional electrocatalyst-based pair-electrosynthesis system for the coproduction of H2 O2 and formate feedstocks.