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

Abstract

H 2 O-covered effect strongly enhanced ΔG(H*) Gibbs free energy of hydrogen adsorption, and two different types of H 2 formation and desorption are observed. • H 2 O-covered effect strongly enhanced ΔG(H*) Gibbs free energy. • Two different types of H 2 formation and desorption are observed. • A careful comparison between the explicit and implicit solvent models is made. The widely-held MN 4 @GR (metal doped nitrogen-contained graphene) model with low ΔG(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 ΔG(H*), we present another additional descriptor of H 2 formation and desorption energy barriers on eight MN x @GR (M = Fe, Co, Rh, Ir, Ni, Pd, Pt, and Cu; x = 0–4) catalysts with and without H 2 O-covered effect. Using density functional theory calculations, ΔG(H*) is strongly enhanced with almost one order of magnitude in the presence of the H 2 O-covered effect. Two different types of H 2 formation and desorption are observed on these eight MN x @GRs with labelling as the one-step and two-step desorption mechanisms. The H 2 O-covered FeN 4 @GR and H 2 O-covered CuN 4 @GR represent two different desorption types with the lowest diffusion and desorption barriers, which indicates the best HER performance.