Hydrogenation temperature related inner structures and visible-light-driven photocatalysis of N-F co-doped TiO ₂ nanosheets

A systematic study has been devoted to prepare N-F co-doped anatase TiO ₂ nanosheets with further hydrogenation treatment at different temperatures. The hydrogenation temperature plays a significant role in changing the inner structure of TiO ₂ from N-F co-doping to the truly hydrogenated characteristic, resulting in various bandgap structures with different light absorption ability and photogenerated electron-hole pair separation efficiency. Moreover, the visible-light-driven photocatalytic activity not only depend on the light absorption ability, but also affected by the amount of defect states significantly. Results indicate that isolated defect state will serve as photogenerated electron-hole pair recombination center, while a large amount of combined defect states will truly reduce the bandgap, enhance the light absorption and the photogenerated electron-hole pair separation efficiency. The photocatalyst hydrogenated at 500 C, which has a specific bandgap structure, gives the highest ability in the degradation of phenol under the visible light irradiation. This simple investigation is of great significance for the design and preparation of anion modified TiO ₂ -based photocatalysts with specific crystal structures to make sufficient use of the visible light for environment protection.