▎ 摘　　要

In this study, the catalytic activities of oxygen reduction reaction (ORR) on a series of transition metal-N-4-graphene (M-N-4-C) composites, comprising 3d (Cr-Ni), 4d (Mo-Ag) and 5d (Os-Au) transition metals have been investigated by using the density functional theory. Our results indicated that the adsorption energy of oxygen atom is the key factor to describe the catalytic activity. For ORR, the highest activity was achieved at the oxygen adsorption energy of 2.25 eV. M-N-4-C (M = Co, Rh and Ir) composites with appropriate oxygen adsorption strength exhibited high ORR activity. In addition, the Co-N-4-C and Rh-N-4-C composites with the oxygen adsorption strength close to 2.78 eV are also predicted to have excellent performance for oxygen evolution reaction (OER).