Photocatalytic activity of Al/Ni doped TiO2 films synthesized by sol-gel method: Dependence on thickness and crystal growth of photocatalysts

Abstract

Al and Ni doped TiO2 thin films were prepared via sol-gel dip-coating method. The effect of the photocatalysis process on the properties of TiO2 based thin films was investigated. The TiO2 based films were annealed at 450 °C. XRD results show that un-doped TiO2 films were grown with anatase phase, whereas, the Ni and Ni/Al doped TiO2 films show anorthic structure of Ti4O7 single phase. The presence of Al preferred the rutile phase. No phases related to NiO or Al2O3 were detected. Ni/TiO2 photocatalyst shows high photocatalytic activity (∼93%) of Methylene blue (MB) breakdown thanks to the high content of O and Ti, wide band gap (3.35 eV), low crystalline size (6.87 nm), high film thickness (288 nm), and high surface roughness (44.5 nm). After photocatalysis, all the films show a decrease in O content and thickness, whereas the indirect band gap values were increased which suggests the reuse with low photocatalytic activity.