Carbon Black-Supported Single-Atom Co-N-C as an Efficient Oxygen Reduction Electrocatalyst for H2O2 Production in Acidic Media and Microbial Fuel Cell in Neutral Media

Abstract

Single metal atom isolated in nitrogen-doped carbon materials (M-N-C) are effective electrocatalysts for oxygen reduction reaction (ORR), which produces H2O2 or H2O via 2-electron or 4-electron process. However, most of M-N-C catalysts can only present high selectivity for one product, and the selectivity is usually regulated by complicated structure design. Herein, a carbon black-supported Co-N-C catalyst (CB@Co-N-C) is synthesized. Tunable 2-electron/4-electron behavior is realized on CB@Co-N-C by utilizing its H2O2 yield dependence on electrolyte pH and catalyst loading. In acidic media with low catalyst loading, CB@Co-N-C presents excellent mass activity and high selectivity for H2O2 production. In flow cell with gas diffusion electrode, a H2O2 production rate of 5.04 mol h−1 g−1 is achieved by CB@Co-N-C on electrolyte circulation mode, and a long-term H2O2 production of 200 h is demonstrated on electrolyte non-circulation mode. Meanwhile, CB@Co-N-C exhibits a dominant 4-electron ORR pathway with high activity and durability in pH neutral media with high catalyst loading. The microbial fuel cell using CB@Co-N-C as the cathode catalyst shows a peak power density close to that of benchmark Pt/C catalyst.