Molten salt construction of stable oxygen vacancies on TiO2 for enhancement of visible light photocatalytic activity

Abstract

The construction of defects on TiO2 surface has attracted great interest due to their prominent effect on photocatalytic activity. However, most synthesis methods often lead to unstable oxygen vacancies which limits their effect for improvement of visible light photoactivity. In this work, stable oxygen vacancies were successfully introduced in commercial TiO2 (P25) via one-step molten salt (MS) method. Due to the incomplete combination of trifluoroacetic acid (TFA) adsorbed on TiO2 in MS, the lattice oxygen atoms of TiO2 were consumed resulting in the formation of oxygen vacancies both on the surface and in the bulk of TiO2. The optical adsorption edge of oxygen defective TiO2 showed a substantial shift toward to visible light region combining with a color variation from white to dark blue. Meanwhile, the morphology and crystalline phase were also changed because of the presence of oxygen vacancies. As a result, the blue TiO2 with rich oxygen vacancies exhibited a considerably enhanced photocatalytic activity for decomposition of rhodamine B (RhB) and selective oxidation of benzyl alcohol under visible light irradiation.