Two-electron Reduction Research Articles

Efficient H2O2 photocatalysis by a novel organic semiconductor with electron donor-acceptor interface

Nowadays, considerable attention has been directed towards the two-electron oxygen reduction for the photocatalytic H2O2 production. However, the challenge of insufficient charge separation capacity markedly constrains the rate of H2O2 production. Herein, we designed a donor-acceptor (D-A) interface characterized by rapid charge migration and separation to enhance the photocatalytic H2O2 production. Specifically, naphthalenetetracarboxylic acid-diaminotriazole as an organic molecule has been judiciously chosen as the electron donor, while perylenetetracarboxylic acid serves as the electron acceptor. The novel semiconductor with D-A interface performs markedly strong internal electric field and demonstrates an excellent H2O2 production rate of 3176 μM h−1. The pronounced internal electric field facilitated by the D-A interface effectively expedites charge separation and induces the migration of photogenerated carriers to the O2 reduction sites. This study introduces a novel paradigm for the design of D-A interfacial organic materials aimed at realizing enhanced photocatalytic capabilities.

B–F dual-doped carbon nanotubes for multi-site and high-rate two-electron oxygen reduction reaction electrocatalysis

Electrocatalytic two-electron oxygen reduction reaction (2e−-ORR) to produce hydrogen peroxide (H2O2) is a promising green way to replace the conventional anthraquinone reaction. Non-metallic catalysts are considered as low-cost catalysts due to their excellent stability and versatile surface chemistry. The performance of non-metallic electrocatalysts is usually limited by the limited catalytic active sites on the surface. Here, we report fluorine and boron dual-doped carbon nanotubes (B–F–C) as a metal-free electrocatalyst for H2O2 production, fabricated via a fast microwave treatment. With the synergistic effect of F and B, this strategy can effectively convert carbon and boron atoms on carbon nanotubes into highly active sites. As a result, an H2O2 yield up to 24.3 mol g−1 L−1 is achieved over B–F–C with a stable selectivity of above 90% within 0.2–0.7 V vs. RHE in 0.1 M KOH. Density functional theory (DFT)calculations further confirm that the multiple active sites created by the dual doping of fluorine and boron are the key factor in improving the performance of 2e−-ORR electrocatalysis. Therefore, this work offers a promising prospect for the design and preparation of catalysts with high catalytic activity for H2O2 production and other catalytic areas of industrial significance.

Cation Effects on the Acidic Oxygen Reduction Reaction at Carbon Surfaces.

Hydrogen peroxide (H2O2) is a widely used green oxidant. Until now, research has focused on the development of efficient catalysts for the two-electron oxygen reduction reaction (2e- ORR). However, electrolyte effects on the 2e- ORR have remained little understood. We report a significant effect of alkali metal cations (AMCs) on carbons in acidic environments. The presence of AMCs at a glassy carbon electrode shifts the half wave potential from -0.48 to -0.22 VRHE. This cation-induced enhancement effect exhibits a uniquely sensitive on/off switching behavior depending on the voltammetric protocol. Voltammetric and in situ X-ray photoemission spectroscopic evidence is presented, supporting a controlling role of the potential of zero charge of the catalytic enhancement. Density functional theory calculations associate the enhancement with stabilization of the *OOH key intermediate as a result of locally induced field effects from the AMCs. Finally, we developed a refined reaction mechanism for the H2O2 production in the presence of AMCs.

Stabilizing Monoatomic Two-Coordinate Bismuth(I) and Bismuth(II) Using a Redox Noninnocent Bis(germylene) Ligand.

The formation of isolable monatomic BiI complexes and BiII radical species is challenging due to the pronounced reducing nature of metallic bismuth. Here, we report a convenient strategy to tame BiI and BiII atoms by taking advantage of the redox noninnocent character of a new chelating bis(germylene) ligand. The remarkably stable novel BiI cation complex 4, supported by the new bis(iminophosphonamido-germylene)xanthene ligand [(P)GeII(Xant)GeII(P)] 1, [(P)GeII(Xant)GeII(P) = Ph2P(NtBu)2GeII(Xant)GeII(NtBu)2PPh2, Xant = 9,9-dimethyl-xanthene-4,5-diyl], was synthesized by a two-electron reduction of the cationic BiIIII2 precursor complex 3 with cobaltocene (Cp2Co) in a molar ratio of 1:2. Notably, owing to the redox noninnocent character of the germylene moieties, the positive charge of BiI cation 4 migrates to one of the Ge atoms in the bis(germylene) ligand, giving rise to a germylium(germylene) BiI complex as suggested by DFT calculations and X-ray photoelectron spectroscopy (XPS). Likewise, migration of the positive charge of the BiIIII2 cation of 3 results in a bis(germylium)BiIIII2 complex. The delocalization of the positive charge in the ligand engenders a much higher stability of the BiI cation 4 in comparison to an isoelectronic two-coordinate Pb0 analogue (plumbylone; decomposition below -30 °C). Interestingly, 4[BArF] undergoes a reversible single-electron transfer (SET) reaction (oxidation) to afford the isolable BiII radical complex 5 in 5[BArF]2. According to electron paramagnetic resonance (EPR) spectroscopy, the unpaired electron predominantly resides at the BiII atom. Extending the redox reactivity of 4[OTf] employing AgOTf and MeOTf affords BiIII(OTf)2 complex 7 and BiIIIMe complex 8, respectively, demonstrating the high nucleophilic character of BiI cation 4.

Phosphorylated g-C3N4/sulfur self-doped g-C3N4 homojunction carboxymethyl cellulose beads: An efficient photocatalyst for H2O2 production

The development of highly reusable, affordable, and durable photocatalysts for the production of hydrogen peroxide (H2O2) remained a challenge. In this study, a homojunction photocatalyst (SPGCN) is constructed between phosphorylated g-C3N4 (PCN) and sulfur self-doped g-C3N4 (SCN) using a simple wet impregnation method. Later, the obtained SPGCN homojunction is transformed into hydrogel beads using carboxymethyl cellulose via an effective cross-linking strategy (SPGCN/CMC). The photocatalytic beads displayed a phenomenal H2O2 production of 3.5 mM under visible light illumination for 60 min. The SPGCN/CMC hydrogel beads showed a maximum reusability of 10 cycles with a decline of 1.5 mM H2O2 production. The improved photocatalytic efficiency is indicated by strengthened utilization of visible light via tuning of the band gap, suppressed recombination of electron-hole pairs, and higher separation efficiency through the effective construction of Z-scheme between the phosphorylated carbon nitride and the sulfur-self-doped carbon nitride present in the SPGCN/CMC beads. The mechanistic studies affirmed the dominant role of superoxide radicals in H2O2 production. The photocatalytic H2O2 production followed a highly selective two-electron reduction reaction. Overall, this study highlights the efficient engineering of carbon nitride-based materials towards artificial photosynthesis.

Photocatalytic hydrogen peroxide production from seawater over graphitic carbon nitride supported titanium dioxide quantum dots

Photosynthesis of hydrogen peroxide (H2O2) from seawater, as a promising technique, is in infancy, and faces challenges of deactivation of photocatalyst and disturbance in H2O2 formation due to the coexisting salts in seawater. Herein, graphitic carbon nitride (g-C3N4) nanosheets supported titanium dioxide (TiO2) quantum dots (QDs) are exploited as novel and efficient photocatalysts for H2O2 photoproduction from seawater. An appropriate content of as-prepared TiO2 QDs are highly and uniformly dispersed on the surface of g-C3N4 nanosheets after a neutralization treatment. TiO2 QDs emerge the synergistic effect and the band gaps regulation effect on g-C3N4 to enhance the H2O2 production. The salt ions in the actual seawater also play the positive role. In actual seawater, the photocatalyst obtains 8.38 mM·h−1·g cat−1 of H2O2 productivity, 11.2% of apparent quantum yields (AQY), and good reusability·H2O2 productivity can be further increased into 30.15 and 23.44 mM·h−1·g cat−1, respectively in alkaline environment and with the addition of electron and proton donor ethanol in seawater. Active species and mechanism of the present photocatalytic system in seawater are also clearly clarified. TiO2 QDs supported on g-C3N4 photocatalyst achieved a major channel of two-electron reduction of O2, and an auxiliary channel of single electron reduction of O2 to produce H2O2 in seawater.

Efficient water disinfection accelerated by polymerization-degree-controlled graphitic carbon nitride under visible light

In the quest for continuously raising the quality of drinking water, the exploration for effective photocatalysts to facilitate photocatalytic water disinfection remains an enduring challenge. Here, we demonstrate that by easily adjusting the polymerization degree of graphitic carbon nitride (g-C3N4), g-C3N4 itself can attain an exceptional photoactivity for disinfecting various waterborne bacteria. By synergistically integrating experimental investigations with density functional theory calculations, we propose that fine-tuning the polymerization degree of g-C3N4 confers remarkable attributes conducive to the specific generation of H2O2 through a two-electron reduction pathway. This ultimately culminates in the attainment of efficient water disinfection, that 7-log reduction in E. coli concentration is achieved within 180 min, in the absence of any additional cocatalyst. This work may shed light on developing highly efficient g-C3N4-based photocatalytic disinfectants for water disinfection applications.

Boosting excitons dissociation in defective-rich graphitic carbon nitride for efficient hydrogen peroxide photosynthesis and on-site environmental governance

Solar-driven hydrogen peroxide (H2O2) production offers a sustainable strategy to address the ever-growing demand of eco-friendly oxidant and clean fuel, while its efficiency highly relies on the generation of desired reactive oxygen species (ROSs). Herein, we demonstrate that introducing boron-nitrogen vacancy (B-NV) associates in g-C3N4 enables to weaken the robust excitonic effect and promote bound excitons spontaneously dissociating into free charge carriers under ambient conditions. Specifically, the doped B atoms introduced a donor state below the conduction band of g-C3N4, which disturbs charge distribution around heptazine rings and further destabilizes excitons. The concomitant NV, serving as an accepter state locating above the valence band, cooperates with the doped B atoms to form B-NV associates that simultaneously downshifts the conduction band and valence band of g-C3N4. Distinct from the counterpart preferring to activate O2 into 1O2 via an energy-transfer-involved pathway, g-C3N4 featuring with B-NV associates displayed a superior photoactivity of visible-light-driven two-electron oxygen reduction reaction for H2O2 production with a yield of 182 μmol h−1 and selectivity of 100%. The produced H2O2 could effectively degrade organic contaminants and kill typical bacteria. This study highlights the importance of ROSs generation in two-dimensional photocatalysts for sustainable solar-to-chemical conversion and on site environmential governance.

Crystal and Molecular Structure of The Mixed-Metal Manganese(II) and Cobalt(II) Maleate Complex: [CoхMn1-x(OOCCH=CHCOO).(H2O)2

For the first time, by the interaction of cobalt maleate tetrahydrate with Mn(II) acetate, a polymeric polynuclear mixed-metal maleate complex of manganese(II) and cobalt(II) was obtained: [CoхMn1-x(OOCCH=CHCOO).(H2O)2]n. The composition and structure of the resulting complexes were studied by IR spectroscopy, UV-Vis spectroscopy, EPR, and elemental and thermogravimetric analysis. The crystal structure of the complex was established by X-ray diffraction. The results of X-ray diffraction analysis showed that maleic acid dianions coordinate with Mn(II) and Co(II) ions in the bidentate bridging form, forming seven-membered chelate rings with manganese and cobalt ions. Each metal ion achieves octahedral symmetry with coordination from two oxygen atoms of two water molecules and two bridging oxygen atoms of the maleate ligands of neighboring complex molecules. The electronic absorption spectra show the absorption band at 965 nm, which should be attributed to the Mn(II) complex. The band at 516 nm refers to the cobalt complex. In the EPR spectrum, a wide single band with g = 2.031 is observed, indicating an electronic exchange interaction between Mn(II) and Co(II) ions. The presence of two metal ions in the complex was also confirmed by cyclic voltammetry. The voltammograms clearly show two reduction waves related to the two-electron reduction of Co2+ (Ec= -0.69 V) and Mn2+ (Ec= -0.985 V) ions.

Hydrogen Peroxide Electrosynthesis in a Strong Acidic Environment Using Cationic Surfactants.

The two-electron oxygen reduction reaction (2e--ORR) can be exploited for green production of hydrogen peroxide (H2O2), but it still suffers from low selectivity in an acidic electrolyte when using non-noble metal catalysts. Here, inspired by biology, we demonstrate a strategy that exploits the micellization of surfactant molecules to promote the H2O2 selectivity of a low-cost carbon black catalyst in strong acid electrolytes. The surfactants near the electrode surface increase the oxygen solubility and transportation, and they provide a shielding effect that displaces protons from the electric double layer (EDL). Compared with the case of a pure acidic electrolyte, we find that, when a small number of surfactant molecules were added to the acid, the H2O2 Faradaic efficiency (FE) was improved from 12% to 95% H2O2 under 200 mA cm-2, suggesting an 8-fold improvement. Our in situ surface enhanced Raman spectroscopy (SERS) and optical microscopy (OM) studies suggest that, while the added surfactant reduces the electrode's hydrophobicity, its micelle formation could promote the O2 gas transport and its hydrophobic tail could displace local protons under applied negative potentials during catalysis, which are responsible for the improved H2O2 selectivity in strong acids.

Carbon Catalysts Empowering Sustainable Chemical Synthesis via Electrochemical CO2 Conversion and Two-Electron Oxygen Reduction Reaction.

Carbon materials hold significant promise in electrocatalysis, particularly in electrochemical CO2 reduction reaction (eCO2 RR) and two-electron oxygen reduction reaction (2e- ORR). The pivotal factor in achieving exceptional overall catalytic performance in carbon catalysts is the strategic design of specific active sites and nanostructures. This work presents a comprehensive overview of recent developments in carbon electrocatalysts for eCO2 RR and 2e- ORR. The creation of active sites through single/dual heteroatom doping, functional group decoration, topological defect, and micro-nano structuring, along with their synergistic effects, is thoroughly examined. Elaboration on the catalytic mechanisms and structure-activity relationships of these active sites is provided. In addition to directly serving as electrocatalysts, this review explores the role of carbon matrix as a support in finely adjusting the reactivity of single-atom molecular catalysts. Finally, the work addresses the challenges and prospects associated with designing and fabricating carbon electrocatalysts, providing valuable insights into the future trajectory of this dynamic field.

Mesoporous carbon spheres with programmable interiors as efficient nanoreactors for H2O2 electrosynthesis

The nanoreactor holds great promise as it emulates the natural processes of living organisms to facilitate chemical reactions, offering immense potential in catalytic energy conversion owing to its unique structural functionality. Here, we propose the utilization of precisely engineered carbon spheres as building blocks, integrating micromechanics and controllable synthesis to explore their catalytic functionalities in two-electron oxygen reduction reactions. After conducting rigorous experiments and simulations, we present compelling evidence for the enhanced mass transfer and microenvironment modulation effects offered by these mesoporous hollow carbon spheres, particularly when possessing a suitably sized hollow architecture. Impressively, the pivotal achievement lies in the successful screening of a potent, selective, and durable two-electron oxygen reduction reaction catalyst for the direct synthesis of medical-grade hydrogen peroxide disinfectant. Serving as an exemplary demonstration of nanoreactor engineering in catalyst screening, this work highlights the immense potential of various well-designed carbon-based nanoreactors in extensive applications.

In Situ Generation of H2O2 over MoOx Decorated on Cu2O@CuO Core-Shell Particle Nanoarchitectonics for Boosting Photocatalytic Oxidative Desulfurization.

Photocatalytic oxidation desulfurization (PODS) has emerged as a promising, ecofriendly alternative to traditional, energy-intensive fuel desulfurization methods. Nevertheless, its progress is still hindered due to the slow sulfide oxidation kinetics in the current catalytic systems. Herein, we present a MoOx decorated on a Cu2O@CuO core-shell catalyst, which enables a new, efficient PODS pathway by in situ generation of hydrogen peroxide (H2O2) with saturated moist air as the oxidant source. The photocatalyst delivers remarkable specific activity in oxidizing dibenzothiophene (DBT), achieving a superior rate of 7.8 mmol g-1 h-1, while maintaining a consistent performance across consecutive reuses. Experimental investigations reveal that H2O2 is produced through the two-electron oxygen reduction reaction (ORR), and both H2O2 and the hydroxyl radicals (•OH) generated from it act as the primary reactive species responsible for sulfide oxidation. Importantly, our catalyst accomplishes complete PODS of real diesel fuel, underscoring an appealing industrial prospect for our photocatalyst.

Constructing Z-Scheme 3D WO3@Co2SnO4 Heterojunction as Dual-Photocathode for Production of H2O2 and In-Situ Degradation of Organic Pollutants

As photoelectrochemical catalyst material, Z-scheme heterojunction 3D WO3@Co2SnO4 composites were designed through a hydrothermal-calcination method. The morphology and structure were characterized by SEM, EDS, XRD, XPS, DRS, and Mott–Schottky analysis, and the photoelectrochemical properties were explored with the transient photocurrent and electrochemical impedance. The construction of Z-scheme heterojunction markedly heightened the separation efficiency of photogenerated electron-hole pairs of WO3 and enhanced the light absorption intensity, retaining the strong redox ability of the photocatalyst. The 3D WO3@Co2SnO4 was used as a photocathode for production of H2O2. Under the optimal reaction conditions, the yield of H2O2 can reach 1335 μmol·L−1·h−1. The results of free radial capture and rotating disc test revealed the existence of direct one-step two-electron and indirect two-step one-electron oxygen reduction to produce H2O2. Based on the excellent H2O2 production performance of the Z-scheme heterojunction photoelectrocatalytic material, 3D WO3@Co2SnO4 and stainless-steel mesh were used to construct a dual-cathode photoelectric-Fenton system for in-situ degradation of a variety of pollutants in water, such as dye (Methyl orange, Rhodamine B), Tetracycline, sulfamethazine, and ciprofloxacin. The fluorescence spectrophotometry was used to detect hydroxyl radicals with terephthalic acid as a probe. Also, the photocatalytic degradation mechanism was revealed, indicating the dual-cathode photoelectron-Fenton system displayed satisfactory potential on degradation of different types of environmental pollutants. This work provided insights for designing high-activity photoelectrocatalytic materials to produce H2O2 and provided possibility for construction of a photoelectric-Fenton system without extra additions.

Identifying the two-electron oxygen reduction mechanism on BC3 site in Cl−-containing electrolytes

The electrochemical synthesis of H2O2 has great potential for applications in the treatment of environmental pollution and energy, but the toxic effect of Cl− on the active sites of catalysts has severely limited the application of this technology in these fields. Developing efficient non-metal-doped catalysts represents an effective strategy to address this issue. Although B-doped carbon materials have demonstrated excellent ORR activity, the understanding of the ORR mechanism on B surface sites remains highly controversial, particularly in seawater electrolytes. The influence of Cl− adsorption behavior on the catalytic reaction center mechanism is still unknown. In this paper, catalysts containing the BC3 structure were successfully prepared with an H2O2 yield of 3.55 mol/ (gcat h) in simulated seawater. The DFT results demonstrated that BC3 functions as a 2e− ORR active site, and the presence of Cl− does not poison it. Instead, it promotes the hydrogenation process of *OOH on its surface, further enhancing its ORR performance. The results provide clarity on how the Cl− of the catalytic environment affects the ORR performance and pathway selectivity of non-metallic B-sites. Additionally, the results offer valuable insights for designing electrocatalysts in complex environments.

Enhanced biomimetic catalysis via self-cascade photocatalytic hydrogen peroxide production over modified carbon nitride nanozymes for total antioxidant capacity evaluation

The peroxidase mimics usually requires the addition of exogenous hydrogen peroxide (H2O2), which greatly hinder their practical applications. Herein, through rational co-modification of multiple elements (potassium (K), chlorine (Cl) and iodine (I)), the modified carbon nitride nanomaterials (KCl/KI-CN) could serve as efficient bifunctional catalysts. The multiple elements doping and the incorporation of cyano groups (CN) are deemed to enhance their photocatalytic and peroxidase-like activity, respectively. Based on the photocatalytic function, H2O2 can be produced continuously and steadily via two-electron oxygen reduction over modified carbon nitride under visible light irradiation. Subsequently, the KCl/KI-CN could catalyze the chromogenic substrate by the in-situ produced H2O2. Taking advantage of the bifunctional properties of modified carbon nitride, we for the first time demonstrate a self-cascade catalytic process and apply successfully for the ascorbic acid (AA) detection and versatile total antioxidant capacity (TAC) evaluation. This paper not only prepares an efficiently bifunctional catalyst but also provides a new self-cascade photocatalytic H2O2 production strategy for the peroxidase-like application.

Utilising a Proton-Responsive 1,8-Naphthyridine Ligand for the Synthesis of Bimetallic Palladium and Platinum Complexes.

We present four proton-responsive palladium and platinum complexes, [MCl2 (R PONNHO)] (M=Pd, Pt; R=i Pr, t Bu) synthesised by complexation of PdCl2 or PtCl2 (COD) with the 1,8-naphthyridine ligand R PONNHO. Deprotonation of [MCl2 (tBu PONNHO)] switches ligand coordination from mono- to dinucleating, offering a synthetic pathway to bimetallic PdII and PtII complexes [M2 Cl2 (tBu PONNO)2 ]. Two-electron reduction gives planar MI -MI complexes [M2 (tBu PONNO)2 ] (M=Pd, Pt) containing a metal-metal bond. In contrast to the related nickel system that forms a metallophosphorane [Ni2 (tBu PONNOPONNO)], an unusual phosphinite binding mode is observed in [M2 (tBu PONNO)2 ] containing close phosphinite-naphthyridinone P⋅⋅⋅O interactions, which is investigated spectroscopically, crystallographically and computationally. The presented proton-responsive and structurally-responsive R PONNHO and bimetallic R PONNO complexes offer a novel platform for future explorations of metal-ligand and metal-metal cooperativity with palladium and platinum.

Theoretical Design and Synthesis of Caged Compounds Using X-Ray-Triggered Azo Bond Cleavage.

Caged compounds are frequently used in life science research. However, the light used to activate them is commonly absorbed and scattered by biological materials, limiting their use to basic research in cells or small animals. In contrast, hard X-rays exhibit high bio-permeability due to the difficulty of interacting with biological molecules. With the main goal of developing X-ray activatable caged compounds, azo compounds are designed and synthesized with a positive charge and long π-conjugated system to increase the reaction efficiency with hydrated electrons. The azo bonds in the designed compounds are selectively cleaved by X-ray, and the fluorescent substance Diethyl Rhodamine is released. Based on the results of experiments and quantum chemical calculations, azo bond cleavage is assumed to occur via a two-step process: a two-electron reduction of the azo bond followed by N─N bond cleavage. Cellular experiments also demonstrate that the azo bonds can be cleaved intracellularly. Thus, caged compounds that can be activated by an azo bond cleavage reaction promoted by X-ray are successfully generated.

Recent progress in two-dimensional materials for generation of hydrogen peroxide by two-electron oxygen reduction reaction

Hydrogen peroxide (H2O2) is an important green oxidant with a wide range of applications in wastewater treatment, pulp bleaching and chemical synthesis. In recent years, two-electron oxygen reduction reaction (2e-ORR) is expected to be a greener and safer alternative to the more energy-intensive and also carcinogenic anthraquinone process. Among the various electrocatalysts for 2e-ORR, two-dimensional nanomaterials have special advantages in the electrosynthesis of H2O2 due to their large specific surface area, abundant basal and edge sites, and tunable atomic structure. This review article summarizes the synthesis methods, and the strategies and mechanisms for enhancing 2e-ORR properties of 2D materials. Practical problems and serious challenges faced by 2D nanomaterials in the synthesis and 2e-ORR applications are elaborated. The aim of this review is to provide researchers with an understanding of 2D nanomaterials in electrocatalytic applications and to promote the further development of novel 2D nanoelectrocatalytic materials.

Single-Atom Co─O4 Sites Embedded in a Defective-Rich Porous Carbon Layer for Efficient H2O2 Electrosynthesis.

The production of hydrogen peroxide (H2O2) via the two-electron electrochemical oxygen reduction reaction (2e- ORR) is an essential alteration in the current anthraquinone-based method. Herein, a single-atom Co─O4 electrocatalyst is embedded in a defective and porous graphene-like carbon layer (Co─O4@PC). The Co─O4@PC electrocatalyst shows promising potential in H2O2 electrosynthesis via 2e- ORR, providing a high H2O2 selectivity of 98.8% at 0.6V and a low onset potential of 0.73V for generating H2O2. In situ surface-sensitive attenuated total reflection Fourier transform infrared spectra and density functional theory calculations reveal that the electronic and geometric modification of Co─O4 induced by defective carbon sites result in decreased d-band center of Co atoms, providing the optimum adsorption energies of OOH* intermediate. The H-cell and flow cell assembled using Co─O4@PC as the cathode present long-term stability and high efficiency for H2O2 production. Particularly, a high H2O2 production rate of 0.25molg-1 cath-1 at 0.6V can be obtained by the flow cell. The in situ-generated H2O2 can promote the degradation of rhodamine B and sterilize Staphylococcus aureus via the Fenton process. This work can pave the way for the efficient production of H2O2 by using Co─O4 single atom electrocatalyst and unveil the electrocatalytic mechanism.