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

Electrochemical production of H2O2 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 H2O2 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.

Automated summary

Electrochemical production of H2O2 is an eco-friendly and cost-effective method. Metal-doped carbon-based catalysts are commonly used for 2e-ORR due to their high selectivity. The role of metals and carbon defects in H2O2 production is still unclear. This study obtained a Co-N/O-C catalyst with a Faradaic efficiency greater than 90% in alkaline electrolyte by varying the Co loading in the pyrolysis precursor. Detailed studies revealed that carbon atoms in C-O-C groups at defect sites were the active sites for 2e-ORR in the Co-N/O-C catalysts. The direct contribution of cobalt single atom sites and metallic Co for the 2e-ORR performance was negligible, but Co played an important role in the pyrolytic synthesis of the catalyst.