Mechanisms of Oxygen Reduction Reaction on Nitrogen-Doped Graphene for Fuel Cells

TLDR

Graphene and its derivatives are attractive for fuel cell electrocatalysis due to their unique structures and electronic properties, and nitrogen doping introduces asymmetry in spin and charge densities that enhances electron‑catalytic activity for the ORR. Density functional theory was used to study the electrocatalytic mechanism of nitrogen‑doped graphene in acidic media. DFT simulations reveal that oxygen reduction on N‑doped graphene proceeds via a spontaneous direct four‑electron pathway, with active sites characterized by high positive spin or atomic charge density.

Abstract

Graphene and its derivatives are attractive for electrocatalytical application in fuel cells because of their unique structures and electronic properties. The electrocatalytical mechanism of nitrogen doped graphene in acidic environment was studied by using density functional theory (DFT). The simulations demonstrate that the oxygen reduction reaction (ORR) on N-doped graphene is a direct four-electron pathway, which is consistent with the experimental observations. The energy calculated for each ORR step shows that the ORR can spontaneously occur on the N-graphene. The active catalytical sites on single nitrogen doped graphene are identified, which have either high positive spin density or high positive atomic charge density. The nitrogen doping introduces asymmetry spin density and atomic charge density, making it possible for N-graphene to show high electroncatalytic activities for the ORR.