Deactivation of the TiO2 photocatalyst by coupling with WO3 and the electrochemically assisted high photocatalytic activity of WO3

Patterned TiO2 stripes were formed on a sol-gel crystalline WO3 film by using a chemically modified sol-gel method (pat-TiO2/WO3), and the coupling effect on the photocatalytic activity was studied. Although the photoinduced electron transfer from TiO2 to WO3 was confirmed by labeling and visualization of the reduction sites with Ag particles, the photocatalytic activities of TiO2 for both the gas-phase oxidation of CH3CHO and the liquid-phase oxidation of 2-naphthol decreased significantly with the coupling. This finding was rationalized in terms of the decrease in the rate of the electron transfer from the semiconductor(s) to O-2 with the coupling, which was estimated from the kinetic analysis of the photopotential relaxation. When the excited electrons were removed by a SnO2 underlayer, the WO3 film exhibited a high photocatalytic activity exceeding that of TiO2 for the oxidation of 2-naphthol.