A simple sol–gel hydrothermal method for the synthesis of defective TiO2 nanocrystals with excellent visible-light photocatalytic activity

Defective TiO2 nanocrystals (D-TiO2) were synthesized by a simple, mild and green sol–gel hydrothermal method. The as-prepared sample possesses a high specific surface area of 173.6 m2/g and high crystallinity of anatase phase without any calcination. Raman, EPR and XPS spectrum confirmed the existence of oxygen vacancies in D-TiO2. These oxygen vacancies provide D-TiO2 with visible-light photocatalytic activity, as demonstrated by the degradation of Rhodamine B (RhB). The degradation pathway of RhB over D-TiO2 was investigated, and the possible photocatalytic mechanism was also proposed. The excellent photocatalytic property of D-TiO2 was mainly attributed to the synergistic effect between the high surface area and abundant oxygen vacancies. This work presents a new route to synthesize high-performance visible-light-responsive TiO2 photocatalyst.