▎ 摘　　要

Developing highly active bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is of great significance in energy conversion and storage technologies. In this study, we systematically investigated the OER/ORR electrocatalytic activity of TMN4@G system by using density functional theory (DFT) calculations. Globally, IrN4@G is a very promising bifunctional catalyst for both OER and ORR with the extremely low overpotentials of 0.30 and 0.26 V, respectively. Such outstanding electrocatalytic performance is mainly attributed to the synergistic effect of Ir and N. More importantly, by constructing 2D activity volcano plots, we obtained the limiting overpotentials of TMN4@G system with the values of 0.26 V for OER and 0.24 V for ORR. These findings open up new opportunities for further exploring graphene-based materials for highly efficient OER/ORR electrocatalysts. (C) 2020 Published by ELSEVIER B.V. and Science Press on behalf of Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences.