Formation of Polysulfides from Consolidation of Cu Vacancies on CuS (001) Surfaces

Abstract

Cu vacancies on CuS surfaces are very important for their properties, and the detailed structures are not very clear yet. In this study, we have systematically studied the structure and stability of CuS (001) surfaces with vacancies using the DFT + U method. The cleavage of CuS along the <001> direction affords a pair of asymmetric surfaces slab1 (featured by S 2− on the surface) and slab2 (featured by S 2 2− on the surface). Our calculation predicts that the surface defects would induce polysulfide formation on slab1 and the driving force increases with the concentration of the vacancies. As a comparison, the polysulfide formation on slab2 is much more challenging. Further mechanistic studies suggest that the polysulfide formation on slab1 is kinetically feasible. The electronic and geometric features of the polysulfide, as well as the difference between slab1 and slab2, have also been discussed in detail.

Mechanisms of Gas-Phase Mercury Immobilized by Metal Sulfides from Combustion Flue Gas: A Mini Review

“…Surface S sites can be classified into lattice S sites, defective S sites, and surface polysulfur (S n 2– , where n ≥ 2) sites according to their coordination environment (Figure ). The exposed S sites over an ideal stable surface usually belongs to lattice S sites, such as the quadruple-coordinated S sites on the CuS(001) surface or the triple-coordinated S sites on the ZnS(110) surface .…”

“…Through amorphizing cobalt sulfide and MoS 3 , abundant S 2 2– sites were detected, which were the major active sites for Hg 0 oxidation. , On the basis of the DFT calculations, the elevation of the Cu vacancy concentration could facilitate the transformation of lattice/defective S sites to S n 2– sites over the CuS(001) surface (Figure ). Thus, the formation of S n 2– sites has a certain degree of connection with surface vacancies, but the formation mechanism of S n 2– sites over metal sulfides needs to be further investigated to guide adsorbent design.…”