Recent advances in single-atom catalysts for acidic electrochemical oxygen reduction to hydrogen peroxide

Electrochemical acidic oxygen reduction reaction (ORR) via 2e- pathway is a promising approach to produce hydrogen peroxide (H2O2). Among them, single-atom catalysts are widely used for acidic ORR to generate H2O2 due to some unique advantages, such as their maximum atom utilization efficiency, tunable electronic structure, and excellent catalytic performance. It is urgent to summarize the use of SACs for acidic ORR to H2O2, especially the systematic elaboration of their catalytic mechanism and structure-activity relationship. Herein, the synthesis, characterization and catalytic mechanism of SACs including some noble metal and transition metal SACs for acidic ORR to H2O2 are systematically described. Some important activity descriptors, especially the regulation methods for the binding energy of key oxygenated intermediates, are highlighted. Finally, the challenges and outlooks of acidic ORR to H2O2 using SACs are proposed. It is hoped that this review is helpful to elucidate the important role of SACs in the electrosynthesis of H2O2 and provide assistance for the design of efficient catalysts.