Reaction Selectivity for Oxygen Reduction of N-doped Graphene Nanoclusters

It has been investigated the oxygen reduction reaction (ORR) for the N-doped graphene nanoclusters using first-principles calculations within the density functional theory, especially focusing on doping site dependencies. It has been shown that the maximum electrode potentials (U-Max) for the 4e(-) pathway are higher than those for the 2e(-) pathway in all reaction sites. This means that the N-doped graphene nanoclusters have high selectivity for the 4e(-) pathway. For the doping sites close to cluster edges, the value of U-Max significantly depend on the reaction sites. On the other hand, for the doping sites around the center of the cluster, the reaction site dependence is hardly observed. It has been suggested that the graphene nanocluster with an N atom around the center of the cluster has high capability of ORR.