First Principles Study of Morphology, Doping Level, and Water Solvation Effects on the Catalytic Mechanism of Nitrogen‐Doped Graphene in the Oxygen Reduction Reaction

Abstract

AbstractBy using first principles DFT calculations, we reveal oxygen reduction reaction mechanisms in N‐doped graphene (N‐Gr). Considering both the morphology and the concentration of dopant N atoms in bulk and edge N‐Gr forms, we calculate the energies of a large number of N‐Gr model systems to cover a wide range of possible N‐Gr structures and determine the most stable N‐Gr forms. In agreement with experiments, our DFT calculations suggest that doping levels in stable N‐Gr forms are limited to less than approximately 30 at. % N, above which the hexagonal graphene framework is broken. The ground state structures of bulk and edge N‐Gr forms are found to differ depending on the doping level and poisoning of the edge bonds. Oxygen reduction reaction mechanisms are evaluated by using Gibbs free‐energy diagrams with and without water solvation. Our results indicate that N doping significantly alters the catalytic properties of pure graphene and that dilutely doped bulk N‐Gr forms are the most active.