Photocatalytic investigations of TiO₂–P25 nanocomposite thin films prepared by peroxotitanic acid modified sol–gel method

Highlights: • A modified sol–gel method was applied in order to prepare photocatalytically active TiO₂–P25 nanocomposite thin films. • Peroxotitanic acid sol (PTA) was employed to produce TiO₂ and TiO₂–P25 nanocomposite thin films on borosilicate glasses after three dip coatings. • Band-gap investigations were performed on both TiO₂ and TiO₂–P25 nanocomposite thin films revealed negligible difference on their optical property. • The photocatalytic activities of TiO₂–P25 nanocomposite thin films were quite superior in compared with those in TiO₂ thin films. - Abstract: TiO₂ thin films and TiO₂–P25 nanocomposite thin films were synthesized by sol–gel method utilizing peroxotitanic acid sol (PTA). Films were obtained by three dip coatings of sol on borosilicate glasses. The crystalline size and the variation in phase of thin films were determined through X-ray diffraction. The average crystalline size of the films that was in the range of 42 nm showed a reduction in the value by increasing the rutile content. The surface morphology of the films has been characterized utilizing Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Contact-mode atomic force microscopy (AFM). The results of the morphological investigations were completely coincided with the formation of TiO₂–P25 nanocomposite. The optical property of the films has been evaluated by Diffuse Reflection Spectrophotometer (DRS) at the room temperature. The obtained UV–vis spectra for both TiO₂ and TiO₂–P25 thin films had similar maximum wavelengths. The band gap values for the direct and indirect transitions have been measured for the TiO₂ and TiO₂–P25 thin films and the results showed negligible variations. The photocatalytical activity of the films was studied by photodegradation of Reactive Red 222 (RR222) under UV irradiation. The results showed that the photocatalytic efficiency of TiO₂–P25 nanocomposite thin films had enhanced by the addition of rutile phase which was obviously due to the cooperation of TiO₂ and P25 nanoparticles in effective charge transfer process. Additionally, photodegradation rate constant result calculations for the TiO₂–P25 nanocomposite thin films can well exhibit the increase in its photocatalytic performance in comparison with TiO₂ thin films