▎ 摘　　要

Density functional theory calculations were performed to explore the stability and chemistry of active sites, and the mechanism of the ORR in a metal free BN co-doped graphene electrocatalyst. The results show that formation of graphitic G-BCxNy defects is energetically favorable than vacancy induced V-BCxNy defects in graphene. We find O-2 physisorption on G-BC3, G-BC2N and G-BCN2 defects. Thus these defects are unlikely sites that initiate the ORR. In contrast, the chemisorption of ORR species O-2, OOH and O, and the downhill energy landscape of the ORR on G-BN3 sites show that G-BN3 sites are active for the complete 4e(-) reduction of O-2 to 2H(2)O. We furthermore explore the catalytic activity of vacancy induced V-BCxNy defects for the ORR. Much stronger adsorption of O-2 and OH on V-BCxNy sites compared to G-BN3 sites indicates that V-BCxNy sites would likely be blocked by OH and the catalytic activity is limited to G-BN3 sites. Thus, an enhancement in catalytic activity and selectivity of BN co-doped graphene for a net 4e(-) complete O-2 reduction can be achieved by increasing the concentration of G-BN3 defects.