A DFT study of the oxygen reduction reaction mechanism on be doped graphene

Abstract

Graphene despite its high surface area has very limited activity towards the oxygen reduction reaction (ORR), demonstrating selectivity towards the unfavorable two-electron mechanism. We have employed the spin polarized density functional theory method to investigate the oxygen reduction reaction activity of the heteroatom p-type beryllium (Be) doped graphene in gas and aqueous media. The preferred doping sites, active sites and reaction mechanisms available on the doped graphene surfaces were investigated with increasing Be concentrations of 0.03 ML, 0.06 ML and 0.09 ML. Our results reveal that oxygen is physisorbed on bare graphene, however, Be at the lattice sites provides site for oxygen adsorption and ORR. Generally, Be concentration increase in a single honey-comb of graphene from 1 to 2, increasing oxygen activation and dissociation on graphene, compared to their isolated defective counterparts. Considering the conjugated Be defective surfaces, oxygen binds dissociatively on the doped surfaces preferentially in the order 0.06 ML > 0.09 ML > 0.03 ML. Whereby strong binding at the 0.06 ML doped surface corresponds to least charge loss to oxygen. Surfaces with the least affinity for O*, OH* and H2O*, and can transfer the most charges to O2 leading to dissociation (as seen on the 0.03 ML surface), shows the highest reaction activity towards the ORR. From these results surfaces that bind O2 weakly and dissociatively could hold promise for the ORR reaction. Single atom catalyst of Be, based on graphene is promising for the ORR. Graphical abstract