The complete reaction mechanism of H2S desulfurization on an anatase TiO2 (001) surface: a density functional theory investigation

Abstract

The complete reaction mechanism of H₂S desulfurization on anatase TiO₂ (001) surface was elucidated using the plane-wave based density functional theory (DFT) method. The reaction starts from the dissociative adsorption of H₂S on the TiO₂ surface. Subsequently, two competitive routes, H₂O and H₂ formation, were investigated. The activation barriers for H₂O formation range from 11 to 13 kcal mol⁻¹, whereas those for H₂ formation are extremely high in the range of 67–87 kcal mol⁻¹. On the basis of the activation energy barriers, the results indicate that the anatase TiO₂ (001) is very active for H₂S desulfurization to produce H₂O, resulting in S-substitution at the O_2c sites on the TiO₂ (001) surface. Electronic charge analyses indicate that S-doping onto the TiO₂ surface can enhance the photocatalytic activity of TiO₂ by reducing its band gap. In addition, by comparison with other metal oxide catalysts, such as TiO₂ (101), CeO₂ (111), CeO₂ (101), ZnO (1010) and α-Fe₂O₃ (0001), we found that TiO₂ (001) is the most promising catalyst for H₂S desulfurization.