Elaborating Nitrogen and Oxygen Dopants Configurations within Graphene Electrocatalysts for Two-Electron Oxygen Reduction

Abstract

Nitrogen (N) and oxygen (O) doping for carbon-based electrocatalysts is one of the most effective methods for improving the oxygen reduction reaction (ORR). Despite its significance, fundamental studies remain needed to determine the effects of atomic configuration on the two-electron (2e(-)) oxygen reduction. In this study, we investigate the coupling effects between pyrrolic N and the O functional groups, including ether (O-C-O) and carbonyl (C=O), on 2e(-) ORR. The results suggest that the 2e(-) ORR performance depends on the C=O/O-C-O ratio. Among several atomic configurations, the coupling of pyrrolic N with carbonyl O is the most favorable type for the 2e(-) reaction, with 98.3% H2O2 selectivity at 0.0 V (vs the reversible hydrogen electrode) in the alkaline electrolyte. Additionally, this combination exhibits considerably stable performance during long-term (12 h) durability test, demonstrating approximately 100% current retention. The experimental results were further supported by theoretical calculation, exhibiting optimal adsorption free energy of OOH* for the couple of pyrrolic N and carbonyl O.