Photocatalytic behavior of TiO2 thin films prepared by sol–gel process

Titanium dioxide solution was prepared via sol–gel process with and without acetyl acetone (AcAc). The formation of the anatase phase in the thin films using AcAc was initiated at 300 °C while the anatase phase in the thin films without using AcAc began to appear at 100 °C. Surface roughness of the TiO2 films using and without using AcAc ranged from 0.414 to 3.08 nm and from 3.72 to 5.35 nm, respectively. Photocatalytic decomposition rate examined by methylene blue solution showed 80% at 400 °C and 88% at 600 °C for the TiO2 thin films using AcAc. On the other hand, the photocatalytic decomposition rate of the TiO2 thin films without using AcAc showed 80% at 100 °C and 97% at 400 °C, respectively. At the temperature above 400 °C, the photocatalytic activity decreased due to appearance of the rutile phase. Comparison between the TiO2 thin films showing the maximum photocatalytic activity revealed that the TiO2 thin film without using AcAc showed 10% higher photocatalytic decomposition rate from the initial 10 to 120 min as compared with the TiO2 thin film using AcAc, which was closely related to the formation of the anatase phase and the surface roughness.