▎ 摘　　要

Recently, the adsorption and dissociation of oxygen molecule on a metal-free catalyst has attracted considerable attention due to the fundamental and industrial importance. In the present work, we have investigated the adsorption and dissociation of O-2 molecule on pristine and silicon-doped graphene, using density functional theory calculations. We found that O-2 is firstly adsorbed on Si-doped graphene by [2+1] or [2+2] cycloaddition, with adsorption energies of -1.439 and -0.856 eV, respectively. Following this, the molecularly adsorbed O-2 can be dissociated in different pathways. In the most favorable reaction path, the dissociation barrier of adsorbed O-2 is significantly reduced from 3.180 to 0.206 eV due to the doping of silicon into graphene. Our results may be useful to further develop effective metal-free catalysts for the oxygen reduction reactions (ORRs), thus greatly widening the potential applications of graphene. (C) 2012 Elsevier Inc. All rights reserved.