Density functional theory study of SO2-adsorbed Ni(1 1 1) and hydroxylated NiO(1 1 1) surface

Abstract

Spin polarized, DFT+U periodic calculation is used as an effective way to model the adsorption process of SO2 on hydroxylated NiO(111) surface. The adsorption of atomic O and O2 on the clean Ni(111) surface is calculated to investigate the forming process of passive film. The molecular and dissociated adsorptions of H2O on NiO(111) surface are evaluated to construct defect-free hydroxylated NiO(111) surface. The adsorption of SO2 and atomic O on clean Ni(111) surface is also investigated to compare with the adsorption capacity between passive film and substrate. With respect to the single adsorption process of SO2 on defect-free hydroxylated NiO(111) surface, the effects of O vacancy of surface and atomic O closed to the surface are investigated. The calculation results show that there is no chemical adsorption of SO2 on the defect-free hydroxylated NiO(111) surface with or without atomic O. Either single SO2 or SO2 with atomic O prefer adsorbing on the hydroxylated NiO(111) surface with O vacancies. The adsorption behavior is strengthened with the increase of percentage of surface O vacancy. The existence of atomic O leads to the production of SO3 on the hydroxylated NiO(111) surface and strengthens the adsorption capacity of SO2. Furthermore, the results also reveal the relationship between the charge transfer and the adsorption energy of SO2 and atomic O on the hydroxylated NiO(111) surface and clean Ni(111) surface. We inferred that broken passive film susceptibility to corrosion compare with substrate when surface O vacancies aggregate and its concentration large enough.