Abstract

The O2 dissociation after the chemisorption on the metal center of M−N4 moieties in graphene (with M = Mn, Fe, and Co) is addressed by density functional theory calculations. Both minimum energy paths and saddle points for the oxygen reduction reaction (ORR) in the allowed spin states have been identified. Our calculations indicate that ORR can evolve through different spin states, those where the M−O2 adducts are stable. We find that Mn−N4 and Fe−N4 centers in graphene exhibit the lowest O2 dissociation energies of ∼0.7 and 1.1 eV, respectively, over three spin channels, while for Co−N4 we find two spin channels with the same dissociation energy of ~1.6 eV. The O2 dissociation barriers on the Mn−N4 and Fe−N4 centers are comparable to that found on Pt(111), suggesting similar ORR catalytic activity, in agreement with experimental results.