Theoretical insights into multi-metal atoms embedded nitrogen-doped graphene as efficient bifunctional catalysts for oxygen reduction and evolution reactions

The development of high activity bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of great significance in renewable energy conversion and storage. In our study, density functional theory (DFT) is used to explore electrocatalytic mechanisms of dual-metal and tri-metal atoms anchored on graphene monolayer coordinated with pyridine nitrogen atoms. The stability of dual-metal and tri-metal sites is evaluated, and the charge redistribution of doped structures is quantitatively studied through Bader charge analysis. Furthermore, several N-doped graphene configurations with excellent bifunctional activities are screened based on the overpotentials in ORR and OER processes. More importantly, the volcano plots are constructed using appropriate ORR and OER descriptors to analyze and predict catalytic activities of metal/nitrogen co-doped graphene with different configurations. Among them, NiNiCoN9-G has superior bifunctional activities, and the most suitable metal and nitrogen doping association can be predicted. These findings will provide insights into the structure–activity relationship and catalytic mechanisms of doped graphene and offer guidelines for future designs of OER/ORR bifunctional electrocatalysts.