(Invited) Mechanistic Studies of the Oxygen Reduction Reaction Electrocatalyzed By N-Doped Graphitic Carbon Materials

The oxygen reduction reaction (ORR) is a crucial step in biological and industrial energy production. To directly convert fuels to electricity in devices such as fuel cells, electrocatalysts alternative to Pt or Pt alloys have been actively sought after, especially those with high performance, high endurance, and low cost. And for this reason N-doped graphitic carbon materials including carbon black, activated carbon, graphite, nanotubes, graphene, etc. have been intensively studied. Despite the recent progress, mechanistic studies of these materials are particularly difficult due to the inhomogeneity and complexity of the catalysts available. Consequently, our understanding has been mainly empirical, and improvements of the catalysts are primarily based on trial and error.

Herein we present our recent studies on well-defined, N-doped graphene nanostructures for the electrocatalyzed ORR. By combining experimental and theoretical work, we show that a two-electron reduction of the carbon is a key step in activating the oxygen. We also show that the dielectric environment of the catalysts play an important role in dictating the selectivity of the reaction.