First principles study of oxygen reduction reaction mechanisms on N-doped graphene with a transition metal support

Abstract

Using first principles density functional theory calculations, we systematically studied oxygen reduction reactions (ORRs) on N-doped graphene (N-Gr) with and without a Cu metallic support (N-Gr/Cu(111) surface). Our ab-initio calculated free energy diagrams surprisingly show that oxygen molecules are dissociated into two oxygen atoms on the N-Gr/Cu(111) surface, which alters the well-known associative ORR mechanisms on pure graphene and N-Gr. Our results, however, indicate that the mechanistic shift does not directly lead to enhancement of ORR activity once water molecules solvate the N-Gr/Cu(111) surface via substantially stabilized intermediates such as O, OH, and OOH. Our results suggest that transition metal supports can be a promising way to control the ORR mechanism on doped graphene and that the evaluation of ORR activity requires understandings of not only the electronic structures of doped graphene but also the chemical interactions between the intermediates and solvating water molecules.