Electrochemical Oxygen Reduction to Hydrogen Peroxide via a Two-Electron Transfer Pathway on Carbon-Based Single-Atom Catalysts

Electrochemical reduction of oxygen is considered as a new strategy to achieve decentralized preparation of hydrogen peroxide (H2O2) in a green manner. As a promising new type of catalytic material, carbon-based single-atom catalysts can achieve wide-range adjustments of the electronic structure of the active metal centers while also maximize the utilization of metal atoms, toward electrochemical production of H2O2 from the selective two-electron transfer oxygen reduction reaction (ORR). Herein, starting from the reviewing of characterizing methods and reaction mechanisms of ORR via two-electron and four-electron transfer pathways, the vital role of binding strength between OOH intermediate and active sites in determining the activity and selectivity towards H2O2 production is revealed and illustrated. Currently reported carbon-based single-atom catalysts for H2O2 production are systematically summarized and critically reviewed. Moreover, with the underpinning chemistry to improve the overall efficiency, three aspects concerning the central metal atoms, coordinated atoms, and environmental atoms are comprehensively analyzed. Based on the understanding of the most current progresses, some predictions for future H2O2 production via electrochemical routes are offered, which include catalyst designs at atomic levels, new synthesis strategies and characterization techniques, as well as interfacial superwetting interaction engineering at electrode and device levels.