Effective active sites of triangular Mo-S Nano-catalysts from first-principle calculations

Abstract

High density of effective active sites (EASs) is critical for efficient catalysis of hydrogen evolution. Basis on the first-principle calculations, the potential energy surface model was used to explore the mechanism determining the proportion of EASs on the edge of Mo-S nanoparticles. It is found that the large proton affinity of Mo-S nanoparticles leads to the high onset overpotential, while the small electron affinity that attenuates rapidly with increasing hydrogen coverage accounts for the scarce EASs. Substituting S with Se reduces the proton affinity and retards the attenuation of electron affinity. Substituting Mo with Nb increazes the electron affinity and decreaze the proton affinity significantly since the d1 configuration of Nb ions. By substituting all Mo ions with Nb and the edge S ions with Se, the proportion of EASs increazes significantly from 25% to more than 62.5% and the catalytic rate increazes by more than 2 orders of magnitude.