H 2 interaction with S atoms of a MoS 2 modelled catalytic site: electronic density analysis for SH formation

Abstract

Semi-core effective core potential (ECP2) calculations were carried out for Mo 3S 6 and Mo 2S 6 clusters that modelled MoS 2 catalyst surface sites (sulfur sites). The interaction of H 2 with monocoordinated (S m) and bicoordinated (S b) sulfur sites was studied. The topological properties of MoS bonds and the critical points (CP) of the charge density Laplacian (−▿ 2 ϱ( r cp)), in the S valence shell, were analyzed. The results indicate that H 2 is dissociated over sites formed by two neighbor S atoms. The local interaction of H 2 with the S atoms occurs in the region in which there is the highest spin density concentration; i.e., the zone located at the CP maxima of −▿ 2 ϱ spin( r cp). This work shows the importance of calculating the CP of −▿ 2 ϱ( r cp) on the surface atoms to determinate active sites on a surface.