Photocatalytic activity of Al/Ni-doped TiO2 films synthesized by sol-gel method: Effect of sunlight photocatalysis on the catalysts properties

Abstract Photocatalytic activity of semiconductors is affected by the nature of metal dopant. To study the effect of non-transition and transition metal on the physical and optical properties of TiO2 based photocatalysts; Al and Ni-doped TiO2 thin films respectively were prepared via a sol-gel dip-coating method. The effect of the photocatalysis process on the properties of TiO2 based thin films was investigated. The photocatalytic activity was calculated from methylene blue dye degradation under sunlight irradiation. XRD results show that un-doped TiO2 films were grown with anatase phase, whereas, the Ni and Ni/Al-doped TiO2 films show 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%) thanks to the high content of O and Ti, wide bandgap (3.35 eV), low crystal 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 bandgap values were increased which suggesting the reuse with low photocatalytic activity.