Comparing the oxygen reduction reaction on selectively edge halogen doped graphene from quantum mechanics

Recently, edge halogenated graphene-nanosheets (EH-GNS) have been discovered to provide low cost oxygen reduction reaction (ORR) catalysis for alkaline fuel cells. Particularly important is that EH-GNS lead to water as the preferred product whereas undoped graphene leads to peroxide. In order to understand the ORR mechanism, we use density functional theory (DFT) to determine the most probable conformations of the doped graphene after synthesis by ball-milling, to calculate the binding energies of each species, and then to obtain the barriers of each step of the ORR. Our results predict that ORR occurs on the edge of the zigzag with onset potentials of 0.62 (chlorine), 0.66 (bromine), and 0.75 V (iodine) vs. the reversible hydrogen electrode (RHE). Based on our validated theoretical framework, we surveyed other molecules (TeH, BiH₂, SbH₂, OCH₃, SCH₃, SeCH₃) as graphene edge molecules to test for promising ORR catalysts, predicting that SCH₃ would be best.