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

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.