H2O2 Electrosynthesis Research Articles

Flow-Through Electrochemical Membrane Reactor with a Self-Supported Carbon Membrane Electrode for Highly Efficient Synthesis of Hydrogen Peroxide.

In situ electroreduction of O2 to H2O2 by using electrons as reagents is known as a green process, which is highly desirable for environmental remediation and chemical industries. However, the development of a cost-effective electrode with superior H2O2 synthesis rate and stability is challenging. A self-supported carbon membrane (CM) was prepared in this study from activated carbon and phenolic resin by carbonization under a H2 atmosphere. It was employed as the cathode to build a flow-through electrochemical membrane reactor (FT-ECMR) for electrosynthesis of H2O2. The results showed that the CM had a small pore size (34 nm), a high porosity (42.3%), and a high surface area (450.7 m2 g-1). In contrast to most of the state-of-the-art self-supported carbon electrode reported in the previous works, the FT-ECMR exhibited a high concentration of continuous and stable H2O2 electrosynthesis (1042 mg L-1) as well as a H2O2 synthesis rate of 5.21 mg h-1 cm-2. It had also demonstrated a high oxygen conversion (0.37%) and current efficiency (88%). The outstanding performance of the FT-ECMR for H2O2 synthesis was attributed to the enhanced mass transfer of the reactor, the existence of a relatively high surface area of CM, and the abundant disordered carbon structures (sp3-C, defects, and edges). In conclusion, our work highlighted using the FT-ECMR with the CM to synthesize H2O2 efficiently and cost-effectively.

Recycle graphite from spent lithium-ion batteries for H2O2 electrosynthesis.

On-site H2O2 synthesis via the two-electron route oxygen reduction reaction for environmental remediation is attractive. This work offers a novel strategy for both spent graphite recovery and H2O2 electrosynthesis catalyst preparation. The graphite is directly recycled from spent lithium-ion batteries to an H2O2 electrosynthesis catalyst. From the view of sustainable development and environmental protection, the H2O2 electrosynthesis catalyst prepared using spent graphite is eco-friendly and cost-efficient. The surface functional groups of the recycled graphite are finely tuned by the HNO3 medium to induce -COOH and C-O-C groups. The activated graphite exhibits high H2O2 activity and selectivity, compared to the raw spent graphite. The activated graphite can achieve an H2O2 Faradic efficiency of about 80%. The activated graphite has a good prospect for T-acid wastewater treatment as the H2O2 generation catalyst. Almost 92% of chemical oxygen demand can be removed.

Highly efficient electrosynthesis of H2O2 in acidic electrolyte on metal-free heteroatoms co-doped carbon nanosheets and simultaneously promoting Fenton process

Recently electrochemical synthesis of H2O2 through oxygen reduction reaction (ORR) via 2e− pathway is considered as a green and on-site route. However, it still remains a big challenge for fabricating novel metal-free catalysts under acidic solutions, since it suffers from high overpotential due to the intrinsically week *OOH adsorption. Herein, a co-doped carbon nanosheet (O/NC) catalyst toward regulating O and N content was synthesized for improving the selectivity and activity of H2O2 electrosynthesis process. The O/NC exhibits outstanding 2e− ORR performance with low onset potential of 0.4 V (vs. RHE) and a selectivity of 92.4% in 0.1 mol/L HClO4 solutions. The in situ electrochemical impedance spectroscopy (EIS) tests reveals that the N incorporation contributes to the fast ORR kinetics. The density functional theory (DFT) calculations demonstrate that the binding strength of *OOH was optimized by the co-doping of oxygen and nitrogen at certain content, and the O/NCCOOH site exhibits a lower theoretical overpotential for H2O2 formation than OCCOOH site. Furthermore, the promoted kinetics for typical organic dye degradation in simultaneous electron-Fenton process on O/NC catalyst was demonstrated particularly for broadening its environmental application.

Oxygen-assisted one-step fabrication and concomitant regulation of hierarchical carbon nanosheet assemblies with conjugated binding configurations for promoted H2O2 electrosynthesis

Electrochemical two-electron oxygen reduction reaction (2e- ORR) is a straightforward and efficient route for H2O2 production. The facile fabrication and concomitant modulation of metal-free carbon with conjugated binding configurations is currently an essential obstacle for 2e− ORR toward electrochemical H2O2 generation. Herein, hierarchical porous O, N co-doped porous carbon (ONPC) nanosheet assemblies with multiple active motifs are developed for driving H2O2 electrogeneration from 2e- ORR. The pyrrolic-N and C = O configurations in ONPC facilitate the highly selective electrosynthesis of H2O2. The synthesis and concomitant regulation of pyrrolic-N and C = O of carbon materials are achieved via a simple one-step oxygen-assisted self-activation, self-template and self-doping strategy. The resulted amorphous ONPC-700 with the optimal pyrrolic − N and C = O active motifs facilitates the 2e− ORR toward H2O2 electrosynthesis. A high H2O2 yield of 0.319 mol g−1 h−1 with 80–93% H2O2 selectivity, good methanol tolerance, and long-term stability in 0.1 M KOH can be achieved. This study inspires to develop and regulate metal-free carbon materials with dual active motifs via one-step oxygen-mediated pyrolysis of low-cost/non-toxic precursor for H2O2 electrosynthesis.

Electrochemical advanced oxidation processes using PbO2 anode and H2O2 electrosynthesis cathode for wastewater treatment

The assessments of a novel electrochemical advanced oxidation process are presented, where PbO2 anode and H2O2 electrosynthesis cathode are simultaneously used in one system. The anode is β-PbO2 coated on a titanium substrate. The cathode is fabricated by rolling the activated Vulcan XC-72R carbon catalyst and PTFE binder on the titanium current collector as the catalyst layer and water-repellent layer, according to different carbon/PTFE ratios. Different electrolysers are used to evaluate the synergistic contributions of the PbO2 anode and H2O2 generated cathode on the pollutant degradation process. The contributions of both direct anodic oxidation and indirect oxidation can be observed. The synergy of the PbO2 anode and H2O2 on-site generated cathode can significantly enhance the oxidation ability and COD removal. Almost all COD in the real pesticide wastewater and dye wastewater can be removed using a PbO2-H2O2 batch electrolyser, which is run at a cell voltage of 3.0 V and at room temperature. The reaction mechanisms in both chloride-containing and sulfate-containing wastewater are discussed particularly.

Continuous On-Site H2O2 Electrosynthesis via Two-Electron Oxygen Reduction Enabled by an Oxygen-Doped Single-Cobalt Atom Catalyst with Nitrogen Coordination.

Single-Co atom catalysts are suggested as an efficient platinum metal group-free catalyst for promoting the oxygen reduction into water or hydrogen peroxide, while the relevance of the catalyst structure and selectivity is still ambiguous. Here, we propose a thermal evaporation method for modulating the chemical environment of single-Co atom catalysts and unveil the effect on the selectivity and activity. It discloses that nitrogen functional groups prefer to proceed the oxygen reduction via a 4e- pathway and notably improve the intrinsic activity, especially when being coordinated with the Co center, while oxygen doping tempts the electron delocalization around cobalt sites and decreases the binding force toward HOO* intermediates, thereby increasing the 2e- selectivity. Consequently, the well-designed oxygen-doped single-Co atom catalysts with nitrogen coordination deliver an impressive 2e- oxygen reduction performance, approaching the onset potential of 0.78 V vs RHE and selectivity of >90%. As an impressive cathode catalyst of an electrochemical flow cell, it generates H2O2 at a rate of 880 mmol gcat-1 h-1 and faradaic efficiency of 95.2%, in combination with an efficient nickel-iron oxygen evolution anode.

Single-atom Iron Catalyst with Biomimetic Active Center to Accelerate Proton Spillover for Medical-level Electrosynthesis of H2 O2 Disinfectant.

Electrosynthesis of H2 O2 has great potential for directly converting O2 into disinfectant, yet it is still a big challenge to develop effective electrocatalysts for medical-level H2 O2 production. Herein, we report the design and fabrication of electrocatalysts with biomimetic active centers, consisting of single atomic iron asymmetrically coordinated with both nitrogen and sulfur, dispersed on hierarchically porous carbon (FeSA -NS/C). The newly-developed FeSA -NS/C catalyst exhibited a high catalytic activity and selectivity for oxygen reduction to produce H2 O2 at a high current of 100 mA cm-2 with a record high H2 O2 selectivity of 90 %. An accumulated H2 O2 concentration of 5.8 wt.% is obtained for the electrocatalysis process, which is sufficient for medical disinfection. Combined theoretical calculations and experimental characterizations verified the rationally-designed catalytic active center with the atomic Fe site stabilized by three-coordinated nitrogen atoms and one-sulfur atom (Fe-N3 S-C). It was further found that the replacement of one N atom with S atom in the classical Fe-N4 -C active center could induce an asymmetric charge distribution over N atoms surrounding the Fe reactive center to accelerate proton spillover for a rapid formation of the OOH* intermediate, thus speeding up the whole reaction kinetics of oxygen reduction for H2 O2 electrosynthesis.

Electro-Fenton process with scalable modified carbonaceous electrode material processed by direct calcination for refractory organic pollutant degradation

Electro-Fenton (EF) regarded as a green substitution to traditional homogeneous Fenton, produces highly oxidizing OH through in-situ H2O2 electrosynthesis and electrochemical Fe2+ regeneration. One of obstacles that hinders translation of bench-scale EF performance to water treatment practices is the difficulty of scaling up catalyst/electrode preparation in low cost while producing high performance. Here we report scalable preparation of modified carbon catalysts for high-efficiency EF by directly calcinating commercial carbonaceous materials in air. The EF with modified carbon cathode shows high kinetics of 0.296–0.569 min−1 for levofloxacin removal in much wider pH range of 3.0–6.6 using less Fe dosage compared with homogeneous Fenton. This EF system can reduce chemical oxygen demand (COD) of coking wastewater from 312.0 to 99.5 mg L−1 to satisfy wastewater discharge standard in China while consuming low electricity of 1.8–4.9 kWh kg−1 COD−1. We demonstrated the scalability of this EF process by scaling up preparative throughput of catalyst (30 g that can be processed into electrodes with total working areas of 54000 cm2), enlarging electrode size (230 cm−2) and reactor volume with wastewater treatment capacity of 7.2 L/h. This scalability demonstration of EF technology shows the promising potential of achieving low-cost advanced wastewater treatment.

Cu/C Composite Electrocatalysts for Electrochemical Production of Hydrogen Peroxide

Hydrogen peroxide (H2O[Formula: see text] is an important chemical with wide fields of applications in the chemical industry, medicine and environmental protection. The preparation of H2O2 by the oxygen reduction reaction (ORR) via the two-electron pathway has the advantages of simple operation and environmental friendliness. Nevertheless, the kinetics of ORR is relatively slow, and the energy efficiency of electrochemical synthesis of H2O2 is seriously limited by the competitive four-electron pathway. Therefore, the electrosynthesis of H2O2 requires an electrocatalyst with both high catalytic activity and selectivity. In this study, Cu nanoparticles supported on carbon composites (Cu/C) were proposed and had been applied as the catalysts for the electrochemical synthesis of H2O2. Taking advantage of the cross-linking reaction between sodium alginate (SA) and metal ions, Cu nanoparticles were directly supported on carbon materials. The porous structure of carbon materials and the introduction of Cu improved the H2O2 selectivity of the catalysts. In O2-saturated 0.1[Formula: see text]M KOH, the optimized catalyst exhibited good activity with a selectivity of 88–90% in the potential range of 0.2–0.6[Formula: see text]V for the electrosynthesis of H2O2, and the selectivity remained 70% after 6[Formula: see text]h of operation.

Electrosynthesis of Hydrogen Peroxide through Selective Oxygen Reduction: A Carbon Innovation from Active Site Engineering to Device Design.

Electrochemical synthesis of hydrogen peroxide (H2 O2 ) through the selective oxygen reduction reaction (ORR) offers a promising alternative to the energy-intensive anthraquinone method, while its success relies largely on the development of efficient electrocatalyst. Currently, carbon-based materials (CMs) are the most widely studied electrocatalysts for electrosynthesis of H2 O2 via ORR due to their low cost, earth abundance, and tunable catalytic properties. To achieve a high 2e- ORR selectivity, great progress is made in promoting the performance of carbon-based electrocatalysts and unveiling their underlying catalytic mechanisms. Here, a comprehensive review in the field is presented by summarizing the recent advances in CMs for H2 O2 production, focusing on the design, fabrication, and mechanism investigations over the catalytic active moieties, where an enhancement effect of defect engineering or heteroatom doping on H2 O2 selectivity is discussed thoroughly. Particularly, the influence of functional groups on CMs for a 2e- -pathway is highlighted. Further, for commercial perspectives, the significance of reactor design for decentralized H2 O2 production is emphasized, bridging the gap between intrinsic catalytic properties and apparent productivity in electrochemical devices. Finally, major challenges and opportunities for the practical electrosynthesis of H2 O2 and future research directions are proposed.

Efficient conversion of propylene to propylene glycol by coupling H2O2 electrosynthesis and TS-1 thermocatalysis

It is highly desirable to develop an efficient and sustainable strategy for converting propylene into high value-added products under mild conditions. In this work, the tandem oxidation of propylene to propylene glycol was achieved by coupling electrosynthesis of H2O2 by 2e- ORR on an oxygen-doped carbon catalyst with thermocatalytic oxidation of propylene by H2O2 on titanium silicalite-1 (TS-1) in a flow cell. For a composite catalyst with the optimal composition which balances electron transfer and H2O2 mass transport, the selectivity towards propylene glycol and the utilization efficiency of H2O2 can reach 79.7 % and 47.6 %, respectively. The yield of propylene glycol is 4.28 mmol gcat-1h−1. This study provides a promising approach to electrochemical propylene conversion in the future.

Boosting Hydrogen Peroxide Electrosynthesis via Modulating the Interfacial Hydrogen-Bond Environment.

Designing highly efficient and stable electrode-electrolyte interface for hydrogen peroxide (H2O2) electrosynthesis remains highly challenging. Inhibition of the side reaction of competitive 4e- oxygen reduction to H2O is essential to obtain highly selective H2O2 electrosynthesis. Instead of catalyst modification to hinder excessive hydrogenation of H2O2, we propose that the addition of a hydrogen-bond acceptor, dimethyl sulfoxide (DMSO) to the KOH electrolyte enables the improvement of the selectivity and activity of H2O2 electrosynthesis simultaneously. Spectral characterization and molecular simulation confirm that the formation of hydrogen bonds between DMSO and water molecules at the electrode-electrolyte interface can reduce the activity of water dissociation into active H* species. The suitable H* supply environment hinders excessive hydrogenation for the oxygen reduction reaction (ORR), thus improving the selectivity of 2e- ORR and achieving over 90% selectivity of H2O2. This work highlights the importance of regulating the interfacial hydrogen-bond environment by organic molecules as a means of boosting electrochemical performance in aqueous electrosynthesis and beyond.

Boosting Hydrogen Peroxide Electrosynthesis via Modulating the Interfacial Hydrogen‐Bond Environment

AbstractDesigning highly efficient and stable electrode‐electrolyte interface for hydrogen peroxide (H2O2) electrosynthesis remains challenging. Inhibiting the competitive side reaction, 4 e− oxygen reduction to H2O, is essential for highly selective H2O2 electrosynthesis. Instead of hindering excessive hydrogenation of H2O2 via catalyst modification, we discover that adding a hydrogen‐bond acceptor, dimethyl sulfoxide (DMSO), to the KOH electrolyte enables simultaneous improvement of the selectivity and activity of H2O2 electrosynthesis. Spectral characterization and molecular simulation confirm that the formation of hydrogen bonds between DMSO and water molecules at the electrode‐electrolyte interface can reduce the activity of water dissociation into active H* species. The suitable H* supply environment hinders excessive hydrogenation of the oxygen reduction reaction (ORR), thus improving the selectivity of 2 e− ORR and achieving over 90 % selectivity of H2O2. This work highlights the importance of regulating the interfacial hydrogen‐bond environment by organic molecules as a means of boosting electrochemical performance in aqueous electrosynthesis and beyond.

Electro-synthesis of pure aqueous H2O2 on nitrogen-doped carbon in a solid electrolyte flow cell without using anion exchange membrane

The two-electron oxygen reduction reaction (2e-ORR) generates on-site hydrogen peroxide (H2O2) more sustainably than the industrial anthraquinone process. Pure aqueous H2O2 electrosynthesis is the most desirable approach, as it is ready-to-use and pH-adjustable. Recently an innovative dual membrane-based solid-electrolyte flow cell (SE-FCAEM/CEM) was reported [Science, 2019, 366, 226-231], in which the anode and cathode “sandwiched” the cation-exchange-membrane (CEM) and anion-exchange-membrane (AEM), separated by a solid-electrolyte, thus allowing H+ and HO2– ions to recombine to form pure H2O2 in deionized (DI)-water stream. One key research needs to effectively deploy this flow cell is to address the stability and engineering difficulties of using an AEM, creating significant drawbacks in cell performance and lifespan. Here, we report a modified SE-FC without involving AEM (SE-FCAEM-FREE) to achieve better performance of H2O2 electrosynthesis. To validate SE-FCAEM-FREE for industrial-relevant production rates, we first developed a nitrogen-doped-carbon catalyst (N-C) with varied nitrogen-to-carbon ratios. Among all samples, the catalyst N-C(2:3) contains high carbon and a proper nitrogen precursor that boosted its activity, resulting in excellent half-cell performance with faradaic efficiency (FE) above 90% at different pH-electrolytes. Secondly, we optimized the catalyst microenvironment by applying a PTFE layer. The Layered-PTFE (5 wt.%) arrangement suppresses hydrogen evolution reaction (HER) and exhibits a high 2e-ORR activity with high current density of 389 mA cm−2 (about 6.53 mmol cm-2h−1) at 90% FEH2O2 without degradation for a 50-hour durability test.

Amorphous low-coordinated cobalt sulphide nanosheet electrode for electrochemically synthesizing hydrogen peroxide in acid media

This study investigates in-depth the local atomic environment-property relationship of amorphous low-coordination catalysts toward the 2e− oxygen reduction reaction (ORR). Here, an ethanol-assisted slow nucleation strategy was adopted to flexibly regulate the intrinsic activity of CoSx nanostructures for efficient 2e− ORR by oriented control the coordination number of Co. When Co and S form Co-S4 coordination structures, the CuNW@CoS4 exhibits an ultra-low overpotential (0.018 V) with 93 % H2O2 selectivity, and 91 % Faraday efficiency in acidic media at 0.1 VRHE. Furthermore, thus produced H2O2 satisfies in-situ organic pollutants degradation by electro-Fenton. XAS and DFT calculations unveil the S-induced forming of abundant low-coordinated Co atoms as active sites in Co-S4, validating that a favorable d-band energy level of Co center can weaken the OOH* adsorption for accelerating the H2O2 production kinetics. This work is anticipated to enlighten the rational design of high-performance ORR catalysts for practically feasible H2O2 electrosynthesis toward wastewater remediation.

Pulsed Electrolysis of Boron-Doped Carbon Dramatically Improves Impurity Tolerance and Longevity of H2O2 Production

Electrocatalytic water treatment has emerged in the limelight of scientific interest, yet its long-term viability remains largely in the dark. Herein, we present for the first time a comprehensive framework on how to optimize pulsed electrolysis to bolster catalyst impurity tolerance and overall longevity. By examining real wastewater constituents and assessing different catalyst designs, we deconvolute the complexities associated with key pulsing parameters to formulate optimal sequences that maximize operational lifetime. We showcase our approach for cathodic H2O2 electrosynthesis, selected for its widespread importance to wastewater treatment. Our results unveil superior performance for a boron-doped carbon catalyst over state-of-the-art oxidized carbon, with high selectivity (>75%) and near complete recoveries in overpotentials even in the presence of highly detrimental Ni2+ and Zn2+ impurities. We then adapt these fine-tuned settings, obtained under a three-electrode arrangement, for practical two-electrode operation using a novel strategy that conserves the desired electrochemical potentials at the catalytic interface. Even under various impurity concentrations, our pulses substantially improve long-term H2O2 production to 287 h and 35 times that attainable via conventional electrolysis. Our findings underscore the versatility of pulsed electrolysis necessary for developing more practical water treatment technologies.

Phosphorous and selenium tuning Co-based non-precious catalysts for electrosynthesis of H2O2 in acidic media

Electrosynthesis of hydrogen peroxide (H2O2) is an on-site method that enables independent distribution applications in many fields due to its small-scale and sustainable features. The crucial point remains developing highly active, selective and cost-effective electrocatalysts. The electrosynthesis of H2O2 in acidic media is more practical owing to its stability and no need for further purification. We herein report a phosphorus and selenium tuning Co-based non-precious catalyst (CoPSe) toward two-electron oxygen reduction reaction (2e– ORR) to produce H2O2 in acidic media. The starting point of using both P and Se is finding a balance between strong ORR activity of CoSe and weak activity of CoP. The results demonstrated that the CoPSe catalyst exhibited the optimized 2e– ORR activity compared with CoP and CoSe. It disclosed an onset potential of 0.68 V and the H2O2 selectivity 76%-85% in a wide potential range (0–0.5 V). Notably, the CoPSe catalyst overcomes a significant challenge of a narrow-range selectivity for transition-metal based 2e– ORR catalysts. Finally, combining with electro-Fenton reaction, an on-site system was constructed for efficient degradation of organic pollutants. This work provides a promising non-precious Co-based electrocatalyst for the electrosynthesis of H2O2 in acidic media.

Approaching Theoretical Performances of Electrocatalytic Hydrogen Peroxide Generation by Cobalt-Nitrogen Moieties.

Electrocatalytic oxygen reduction reaction (ORR) has been intensively studied for environmentally benign applications. However, insufficient understanding of ORR 2 e- -pathway mechanism at the atomic level inhibits rational design of catalysts with both high activity and selectivity, causing concerns including catalyst degradation due to Fenton reaction or poor efficiency of H2 O2 electrosynthesis. Herein we show that the generally accepted ORR electrocatalyst design based on a Sabatier volcano plot argument optimises activity but is unable to account for the 2 e- -pathway selectivity. Through electrochemical and operando spectroscopic studies on a series of CoNx /carbon nanotube hybrids, a construction-driven approach based on an extended "dynamic active site saturation" model that aims to create the maximum number of 2 e- ORR sites by directing the secondary ORR electron transfer towards the 2 e- intermediate is proven to be attainable by manipulating O2 hydrogenation kinetics.

Approaching Theoretical Performances of Electrocatalytic Hydrogen Peroxide Generation by Cobalt‐Nitrogen Moieties

AbstractElectrocatalytic oxygen reduction reaction (ORR) has been intensively studied for environmentally benign applications. However, insufficient understanding of ORR 2 e−‐pathway mechanism at the atomic level inhibits rational design of catalysts with both high activity and selectivity, causing concerns including catalyst degradation due to Fenton reaction or poor efficiency of H2O2 electrosynthesis. Herein we show that the generally accepted ORR electrocatalyst design based on a Sabatier volcano plot argument optimises activity but is unable to account for the 2 e−‐pathway selectivity. Through electrochemical and operando spectroscopic studies on a series of CoNx/carbon nanotube hybrids, a construction‐driven approach based on an extended “dynamic active site saturation” model that aims to create the maximum number of 2 e− ORR sites by directing the secondary ORR electron transfer towards the 2 e− intermediate is proven to be attainable by manipulating O2 hydrogenation kinetics.

Manganese oxide nanocrystals embedded porous Graphene-like network for electrosynthesis of H2O2 and construction of Self-powered aptasensor

To improve the selectivity and production rate of the H2O2 electrosynthesis, an electrocatalyst was established based on ultrathin graphene-like mesoporous carbon nanosheets embedded with ultra-small manganese oxide (MnOx) nanocrystals (denoted as MnOx@C). A polymer-manganese-metal–organic framework (polyMn-MOF) was used as the precursor for the preparation of the series of MnOx@C hybrid by calcining at different temperature (600, 700, and 800 °C) under nitrogen atomsphere. Density functional theory simulation revealed that MnOx@C-700 obtained by pyrolyzing polyMn-MOF at 700 °C exhibited the optimization adsorption energy of *OOH, thus showing a high H2O2 selectivity of 96.5 % and large limited oxygen reduction current of 2.3 mA cm−2. Meanwhile a high mass activity of 35.56 A g−1 (at 0.4 V vs the reversible hydrogen electrode) and high durability over 10 h were attained for the MnOx@C-700 catalyst. Moreover, the MnOx@C-700-assembled Zn-air battery (ZAB) showed a large open-circuit voltage of 1.34 V and a remarkable peak power density of 2.22 mW cm−2. The constructed ZAB-driven self-powered aptasensor demonstrated a wide linear range of 0.1 pg mL−1–100 ng mL−1 and an ultralow detection limit of 0.08 pg mL−1 toward diethylstilbestrol. This work provided new insights onto the H2O2 electrosynthesis and detection of hazards using the self-powered biosensing strategy.