Surface oxygen vacancies promoted photodegradation of benzene on TiO2 film

Engineering the bulk and surface oxygen vacancy defects in titania (TiO2) photocatalysts has been proved to bean efficient strategy to improve quantum efficiency. In this work, we report a facile and innovative method to manipulate surficial oxygen defects on TiO2 films using calcium hydride (CaH2) as a reducing agent. Surficial oxygen defect formation was verified by the combinations of electron paramagnetic resonance (EPR), Raman and UV–Vis absorption spectroscopy. The concentration of surficial oxygen vacancy defects could easily be tuned by varying the temperature and duration of the CaH2 treatment. After optimization CaH2 treatment conditions, the activity of TiO2 films in photodegrading benzene under UV light was enhanced by as much as 340%. The mechanism of surficial oxygen vacancy defect enhancing photocatalytic performances of TiO2 film was systematically investigated by density functional theory (DFT) calculations, which predict the existence of band bending modelled as a p-n junction between the bulk and the surface layer with oxygen vacancies, thus inhibiting electron-hole recombination, and enabling oxygen transport at different depths for the enhancement of photocatalytic properties.