▎ 摘　　要

Single and paired atomic catalysts have attracted substantial interest due to their excellent catalytic activity toward oxygen reduction reactions (ORR). Herein, a group of dual metal catalysts with various transition metal (TM = Fe, Co, Ni, Cu, Zn, Ru, and Pt) atoms supported on N-doped graphene with a four-atom vacancy (N8V4) were designed and screened for their ability to catalyze ORR. The density functional theory (DFT) method was employed to obtain theoretical overpotentials (eta) to evaluate the performance of each catalyst in comparison with the benchmark catalyst, Pt/C (eta = 0.45 V). The volcano plot of delta G(*OH) versus onset potential was created. Our results showed that RuCo@N8V4, with paired Ru and Co atoms anchored in N8V4 pores, exhibited the best catalytic activity with an overpotential of 0.33 V on the top of volcano, followed by PtCo@N8V4 (0.38 V), ZnCo@N8V4 (0.41 V) and FeCo@N8V4 (0.43 V). Compared with a single Co atom catalyst Co@N8V4 (eta = 0.72 V), it was found that the introduction of the second TM could significantly improve the catalytic performance. This is because the d-band center of the system shifts apart from Fermi energy level, reducing the adsorption of the OH intermediate. Moreover, the local polarization charges of Co and adsorption properties of O-2 molecule are also improved by the nature of the second TM, hence enhancing the catalytic activity of the Co catalyst.