First principles study of adsorption and oxidation mechanism of elemental mercury by HCl over MoS2 (1Â 0Â 0) surface

The Hg oxidation mechanism by HCl over MoS2 (1 0 0) surface was firstly investigated by the density functional theory and the periodic slab model. Hg0 is strongly adsorbed on the Mo top site of MoS2 (1 0 0) surface due to the overlaps between the s, p state of Hg atom and the s, p state of Mo atom. The H-Cl bond of the isolated HCl molecule is destroyed after adsorption on the MoS2 (1 0 0) surface, revealing a chemical dissociated adsorption process. HgCl and HgCl2 is dissociatively adsorbed on the Mo top site, while non-dissociatively adsorbed on the S edge site of MoS2 (1 0 0) surface. Energy pathway analysis indicates that Hg0 oxidation on the MoS2 (1 0 0) surface obeys the Langmuir-Hinshelwood mechanism via the pathway of Hg → HgCl → HgCl2. In the whole Hg oxidation reaction, the formation of HgCl and the dissociation of HgCl2 are the rate-determining steps due to their high energy barriers. The lower energy barrier of the mercury oxidation reaction on MoS2 surface makes it an attractive alternative catalyst for Hg catalytic oxidation.