Theoretical insight into single Rh atoms anchored on N-doped γ-graphyne as an excellent bifunctional electrocatalyst for the OER and ORR: electronic regulation of graphitic nitrogen

Abstract

Reducing the overpotential and increasing the reaction rate, which are respectively determined by the thermodynamics and kinetics of electrocatalysis, are the keys to obtaining high-performance bifunctional electrocatalysts for the OER/ORR. Herein, six late-transition metals (Ru, Rh, Pd, Os, Ir, and Pt) anchored on γ-GY and graphitic N doped γ-GY substrates are screened as electrocatalysts for the OER and ORR via density functional theory, and the effects of electronic regulation due to the presence of graphitic N on the thermodynamics and kinetics of electrocatalysis are investigated in detail. Among the six γ-GY@TM candidates, only γ-GY@Rh exhibits excellent OER activity, with an overpotential of 0.42 V. Furthermore, graphitic N doped graN-γ-GY@Rh shows outstanding bifunctional electrocatalytic activity, with overpotentials of 0.27 V for the OER and 0.33 V for the ORR, which are remarkably superior to the values of 0.43 V for RuO₂ and 0.45 V for noble-metal Pt electrocatalysts. The present results present some of the lowest overpotentials for OER/ORR electrocatalysts given by theoretical studies to date. From a kinetics point of view, N-doping also remarkably reduces the activation energy barriers of the catalytic rate-limiting steps of the OER and ORR, accelerating the reaction processes and significantly improving the conductivity. Our work provides a theoretical strategy for designing high-efficiency bifunctional OER/ORR electrocatalysts based on γ-GY materials.