DFT calculations of double vacancies MoS2 catalyzing water gas shift reaction: S vacancies as electron bridge promote electron transfer to H2O and CO molecules

Abstract

The poor activity of molybdenum disulfide (MoS2) basal plane is the key scientific problem to limit efficient hydrogen production. In this paper, MoS2 with single (VS-MoS2) and double sulfur vacancy (VS, S-MoS2) have been constructed and used for water gas shift reaction (WGSR). Results show that the adsorption energy of VS, S-MoS2 for CO molecule is −1.43 eV, which is 28.6 times and 1.1 times than original MoS2 and VS, S-MoS2, respectively. The energy barrier of the rate-determining step in the association mechanism of VS, S-MoS2 is 1.78 eV, which is 21% lower than pristine MoS2. S vacancies are active sites for CO and H2O adsorption. The delocalized electrons enrichment in S vacancies break the electron transfer barrier between the surface and molecules. Sulfur vacancies as medium make electrons continuously transferred to CO and H2O molecules.