Preparation of nitrogen co-doped SiO₂/TiO₂thin films on ceramic with enhanced photocatalytic activity under visible-light irradiation

In this study, we have successfully deposited N-doped SiO2/TiO2 thin films on ceramic tile substrates by sol–gel method for auto cleaning purpose. After dip coating and annealing process the film was transparent, smooth and had a strong adhesion on the ceramic tile surface. The synthesised catalysts were then characterised by using several analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscope (AFM) and UV-vis absorption spectroscopy (UV-vis). The analytical results revealed that the optical response of the synthesised N-doped SiO2/TiO2 thin films was shifted from the ultraviolet to the visible light region. The nitrogen substituted some of the lattice oxygen atoms. The surface area of co-doped catalyst increased, and its photocatalytic efficiency was enhanced. The photocatalytic tests indicated that nitrogen co-doped SiO2/TiO2 thin films demonstrated higher than of the SiO2/TiO2 activity in decolouring of methylene blue under visible light. The enhanced photocatalytic activity was attributed to an increasing of the surface area and a forming of more hydroxyl groups in the doped catalyst.