Based on first-principles DFT calculations, copper-nitrogen embedded graphene (CuN3-Gra) is introduced as an efficient electrocatalyst for oxygen reduction reaction (ORR) in fuel cells. The possible reaction mechanisms as well as the corresponding stationary points on potential energy surfaces are studied in acidic media. Our results indicate that dissociation of O2 over CuN3-Gra cannot occur at normal condition due to its large energy barrier. In contrast, the O2 hydrogenation into OOH, followed by the hydrogenation of OOH into O and H2O species is the most favorable pathway for the ORR process. The energy barrier for rate-determining step of this reaction is calculated to be 1.00 eV which is related to the formation of first H2O molecule. The free energy diagrams reveal that for OOH hydrogenation pathway, all of the elementary steps are exothermic at potentials 0.0–0.8 V.
