DFT simulation of nitrogen-doped graphene as an ORR catalyst in fuel cells

Abstract

Nitrogen (N) - doped carbon nanosheets have been discovered as a new class of low cost, metal- free Oxygen Redn. Reaction (ORR) catalysts for alk. fuel cells. Nitrogen atoms can be doped into the basal plane of a graphene sheet in either a pyridinic, pyrolic or graphitic configuration, and we compared the three. A better understanding of ORR on this catalyst is needed to det.: i) why this doped catalyst forms water in the preferred 4e ORR mechanism over the peroxide formation found in undoped graphene. ii) how to improve this catalyst, so that ORR can occur in the preferred acidic environment. We used the PBE flavor d. functional theory (DFT) with the SeqQUEST code to calc. the binding energies and onset potential of pyridinic, graphitic, and pyrollic nitrogen to find the optimal configuration that would need to the best onset potential for 4e ORR. We used nudged elastic band (NEB) calcns. in conjunction to predict the potential dependent barriers of the ORR comparing the relative difficulties of making water or peroxide of the different configurations.