Graphene supported single metal atom catalysts for the efficient hydrogen oxidation reaction in alkaline media

The sluggish kinetics of the hydrogen oxidation reaction (HOR) results in an ultra-high Pt loading on the anode of alkaline fuel cell (AFC) systems. Single-atom catalysts (SACs) can maximize the atom utilization efficiency, thus offering a promising strategy for reducing the cost of electrode materials. In this work, we systematically explored the alkaline HOR performance of single noble metal and 3d transition metal atoms anchored on the divacancy graphene (M/G, M = Cr, Mn, Fe, Co, Ni, and Pt) by first-principles density functional theory calculations. The calculations suggested that the alkaline HOR on M/Gs proceeds through the Heyrovsky-Volmer mechanism with the Heyrovsky reaction as the rate-determining step. Both the full free energy profile and H adsorption free energy indicate that all considered M/Gs show superb HOR activity in the order Cr/G < Fe/G < Co/G < Ni/G < Mn/G < Pt/G. However, only Pt/G and Ni/G can maintain high electrochemical stability at the HOR operating potentials, while Mn/G, Cr/G, Fe/G, and Co/G easily suffer from oxidation. Therefore, both Pt/G and Ni/G SACs are promising candidates as anodic HOR electrocatalysts for AFCs.