Preparation of WO3-modified TiO2 thin film by peroxo sol-gel method and its photocatalytic activity in degradation of methylene blue

A series of WO3-modified TiO2 sols with various WO3 contents were synthesized by peroxo sol-gel method using H2O2 as the agent. The as-synthesized WO3-TiO2 sols were light yellow in color. The maximum amount of WO3 which could be incorporated into the TiO2 sol was 4 wt.%. The pH values of the as-prepared sols were near neutral. These sols were very stable even after 2 years in stock. The sols were used to coat on glass substrate. The XRD patterns and the SAED patterns indicated that the phase of TiO2 was anatase. There were no characteristic XRD peaks of WO3 in the WO3-modified TiO2 sol, possibly due to low WO3 loading. The particles were rhombus shaped with the major axis and minor axis of 30-77 nm and 15-31 nm, respectively. WO3 was incorporated into the surface structure of TiO2 and modified the electronic state of Ti. The film coated onto glass substrate was very uniform, and the film thickness was similar to 160 nm. The XPS results exhibited that W existed as 5 + and 6 + oxidation states and Ti existed in Ti3+ and Ti4+. These four chemical states play a role of gathering the photogenerated holes and capturing the photogenerated electrons in the lower conduction band of WO3, respectively. This can effectively enhance the separation rate of photogenerated electron-hole pairs and increase the photoactivity. WO3/TiO2 samples had high photocatalytic activity under UV light illumination to degrade methylene blue, because it had high OH and O2- group contents.