▎ 摘　　要

Density functional theory (DFT) is utilized to compute the thermodynamic free energy changes of the elementary reaction steps of the oxygen reduction reaction (ORR) on TMOxN4-x (TM=Fe, Co and Ni; x= 1-3) single atom catalysts (TMOxN4-x-SACs). Based on thermodynamic stability and catalytic ORR activity, it is found that CoOxN4-x-SACs show relatively good stability and activity. Furthermore, the final reduction reaction step (OH* + H+ + e(-) -> H2O + *) with the largest.G value towards five different CoOxN4-x-SACs is the potential-determining step (PDS). All calculated results suggest that the theoretical overpotential of CoO2N2-opp is munch close to that of Pt (111), implying the optimal electrocatalytic ORR activity among TMOxN4-x-SACs. Furthermore, electronic structure analysis reveals that the d-band center of Co for CoO2N2-opp is located rather far away from the Fermi level (set as zero) and binding states of adsorbed are reduced and the antibinding states of adsorbed OH* fragments are increased, compared with that of other CoOxN4-x-SACs. In conclusion, the introduction of N and O can effectively modify d-band of active metal center and adsorption of oxygen-contained intermediates, thus tune ORR activity.