Toward More Efficient Carbon-Based Electrocatalysts for Hydrogen Peroxide Synthesis: Roles of Cobalt and Carbon Defects in Two-Electron ORR Catalysis.

Electrochemical production of H 2 O 2 is a cost-effective and environmentally friendly alternative to the anthraquinone-based processes. Metal-doped carbon-based catalysts are commonly used for 2-electron oxygen reduction reaction (2e - ORR) due to their high selectivity. However, the exact roles of metals and carbon defects on ORR catalysts for H 2 O 2 production remain unclear. Herein, by varying the Co loading in the pyrolysis precursor, a Co-N/O-C catalyst with Faradaic efficiency greater than 90% in alkaline electrolyte was obtained. Detailed studies revealed that the active sites in the Co-N/O-C catalysts for 2e - ORR were carbon atoms in C-O-C groups at defect sites. The direct contribution of cobalt single atom sites and metallic Co for the 2e - ORR performance was negligible. However, Co plays an important role in the pyrolytic synthesis of a catalyst by catalyzing carbon graphitization, tuning the formation of defects and oxygen functional groups, and controlling O and N concentrations, thereby indirectly enhancing 2e - ORR performance.