The role of F-dopants in adsorption of gases on anatase TiO2 (001) surface: a first-principles study

Abstract

We performed a systematic investigation of adsorption of small gas molecules (O₂, CO, NO, NO₂ and SO₂) on pristine and fluorine doped (F-doped) anatase TiO₂ (001) surface using density functional theory (DFT). Three kinds of F-dopants, which were achieved by substituting a surface O_2C atom (F_I), or a surface O_3C (F_II), or an O_3C atom below a surface Ti_5C with an F atom (F_III), were studied to investigate the effects on the surface properties as well as the adsorption of molecules. The influence of F-dopants on the adsorption energy, charge transfer and magnetic moment of the most stable adsorption configurations of these molecules on the surfaces are thoroughly discussed. Three types of F-dopants were found to significantly promote the adsorption of O₂, NO and NO₂. However, the promotive effect of F_I and F_II dopants was not found upon the adsorption of CO and SO₂. Only the F_III dopant was found to have a promotive effect on the two molecules. The mechanisms of interactions between molecules and surfaces are examined by analyzing their electronic structure and charge transfer. The results show that Ti³⁺ induced by F-dopants plays an important role in enhancing the interaction between gas molecules and TiO₂ surfaces.