Enhanced effect of H2O monolayer on metal doped nitrogen-containing graphene for hydrogen evolution reactions

The widely-held MN4@GR (metal doped nitrogen-contained graphene) model with low & UDelta;G(H*) Gibbs free energy of hydrogen adsorption has attracted much attention because of excellent performance in hydrogen evolution reaction (HER). Besides of the common descriptor of & UDelta;G(H*), we present another additional descriptor of H2 formation and desorption energy barriers on eight MNx@GR (M = Fe, Co, Rh, Ir, Ni, Pd, Pt, and Cu; x = 0-4) catalysts with and without H2O-covered effect. Using density functional theory calculations, & UDelta;G(H*) is strongly enhanced with almost one order of magnitude in the presence of the H2O-covered effect. Two different types of H-2 formation and desorption are observed on these eight MNx@GRs with labelling as the one-step and two-step desorption mechanisms. The H2O-covered FeN4@GR and H2O-covered CuN4@GR represent two different desorption types with the lowest diffusion and desorption barriers, which indicates the best HER performance.