Wetting and photocatalytic properties of Ni-doped TiO2 coating on glazed ceramic tiles under visible light

Highlights: • Ni-doped TiO2 thin film has more uniform morphology than undoped TiO2 thin film. • Ni-doped TiO2 thin film can be active under visible light. • Ni-doped TiO2 coating has band gap about 2.48 eV. • Ni-doped TiO2 thin film illustrated good hydrophilicity after visible light irradiation. - Abstract: In this paper, the influence of Ni doping on the self-cleaning properties of TiO₂ thin film under visible light is reported. The TiO₂ thin films were prepared by using spray coating method. The coated tiles were heat-treated at 550 °C and 650 °C with 15 min soaking. The microstructure, morphology, thickness and ultraviolet-visible (UV–Vis.) light absorbance of the TiO₂ thin films were characterized by grazing-incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FE-SEM) equipped with Energy-dispersive X-ray spectroscopy and UV–Vis. absorption spectroscopy, respectively. Photocatalytic activity and wetting of the TiO₂ thin films contaminated with olive oil were evaluated by measuring the weight loss of the olive oil and water contact angle, respectively. The GIXRD pattern indicated that the transformation of anatase to rutile can be inhibited by 4 wt% of Ni doping. FE-SEM images showed that the Ni-doped TiO₂ thin film has more uniform morphology than the undoped TiO₂ thin film. The UV–Vis. absorbance spectra showed that the Ni-doped TiO₂ thin film has a wavelength of maximum absorbance higher and a band gap lower than the undoped TiO₂ thin film. Thus photocatalytic activity and hydrophilicity were provided under visible light.