Graphene supported single metal atom catalysts for 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. The single-atom catalyst (SAC) can maximize 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 the single noble metal and 3d transition metal atoms anchored on the di-vacancy graphene (M/G, M = Cr, Mn, Fe, Co, Ni, and Pt) by the first-principle density functional theory calculations. The calculations suggested that the alkaline HOR on M/Gs passes 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 with the order Cr/G < Fe/G < Co/G < Ni/G < Mn/G < Pt/G. However, only Pt/G and Ni/G can keep high electrochemical stability under 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 for the anodic HOR electrocatalyst in AFC.