Tuning oxygen vacancy content in TiO2 nanoparticles to enhance the photocatalytic performance

White TiO2 (W-TiO2), gray TiO2 (G-TiO2) and black TiO2 (B-TiO2) have been prepared through simple annealing process in different atmospheres. The oxygen vacancy content in the TiO2 samples and the relationship between oxygen vacancy and photocatalytic performance have been studied by comprehensive analyses. The XRD peaks slightly move to a low angle and the Raman strongest peak shifts positively owing to oxygen vacancy and Ti3+. The energy bandgap of G-TiO2 and B-TiO2 is tuned from 3.10 to 3.02 and 1.99 eV. The content of oxygen vacancy is 1%, 4.8% and 7.8% for W-TiO2, G-TiO2 and B-TiO2, respectively. The efficiency of NO removal is stable at 34%, 38% and 45%, and the decomposition rate of Rhodamine B under visible light is 75%, 83% and 89% for W-TiO2, G-TiO2 and B-TiO2, respectively. The results are significant for the design of high-performance photocatalytic materials in the field of solar energy conversion.