▎ 摘　　要

The searching of highly efficient bifunctional catalysts for both oxygen reduction reaction (ORR) and CO2 reduction reaction (CO2RR) for energy conversion and storage has attracted particular attention in recent years. In this work, through computational design, we have studied both ORR and CO2 RR for RuN4 doped graphene (RuN4-Gra) and modified RuN4-Gra by an oxygen atom (RuN4/O-Gra). For ORR, our calculations indicated that RuN4/O-Gra has better catalytic performance both kinetically and thermodynamically. The calculated energy barrier is 0.39 eV at the rate-determining step, much smaller than 0.80 eV for pure Pt and 0.56 eV for FeN4-Gra. The predicted working potential is 0.54 V, larger than 0.38 V for FeN4-Gra. For CO2 RR, the formation of HCOOH is prevented due to the strong adsorption of CO and strong hydrogen evolution reaction (HER) for RuN4-Gra. However, after the modification of RuN4-Gra with an oxygen atom, the reaction pathway is changed and the formation of CO is prevented. RuN4/O-Gra has high selectivity toward HCOOH, and HER is also prevented. Therefore, RuN4/O-Gra is a highly efficient bifunctional catalyst for both ORR and CO2RR.