Carbon Black‐Supported Single‐Atom CoNC 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 H 2 O 2 or H 2 O 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 H 2 O 2 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 H 2 O 2 production. In flow cell with gas diffusion electrode, a H 2 O 2 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 H 2 O 2 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.