Exploring the Evolution Mechanism of Sulfur Vacancies by Investigating the Role of Vacancy Defects in the Interaction between H(2)S and the FeS(001) Surface

[Image: see text] Vacancy defects are inherent point defects in materials. In this study, we investigate the role of Fe vacancy (V(Fe)) and S vacancy (V(S)) in the interaction (adsorption, dissociation, and diffusion) between H(2)S and the FeS(001) surface using the dispersion-corrected density functional theory (DFT-D2) method. V(Fe) promotes the dissociation of H(2)S but slightly hinders the dissociation of HS. Compared with the perfect surface (2.08 and 1.15 eV), the dissociation energy barrier of H(2)S is reduced to 1.56 eV, and HS is increased to 1.25 eV. Meanwhile, S vacancy (V(S)) significantly facilitates the adsorption and dissociation of H(2)S, which not only reduces the dissociation energy barriers of H(2)S and HS to 0.07 and 0.11 eV, respectively, but also changes the dissociation process of H(2)S from an endothermic process to a spontaneous exothermic one. Furthermore, V(Fe) can promote the hydrogen (H) diffusion process from the surface into the matrix and reduce the energy barrier of the rate-limiting step from 1.12 to 0.26 eV. But it is very hard for H atoms gathered around V(S) to diffuse into the matrix, especially the energy barrier of the rate-limiting step increases to 1.89 eV. Finally, we propose that V(S) on the FeS(001) surface is intensely difficult to form and exist in the actual environment through the calculation results.