Research On The Photocatalytic Performance And Hydrophilicity Of Titania Based Self-cleaning Thin Films

In this paper, the TiO₂ photocatalytic self-cleaning thin films were prepared viainorganic sol-gel method. The microstructures such as crystal structure, surfacemorphology and band structures of TiO₂ thin films were controlled by the metalmodifying method so that the the visible light photocatalytic performance wasenhanced. In order to enhance the hydrophilicity of TiO₂ thin films,polyethyleneglycol and SiO₂ sol were added into TiO₂ sol to change the surfacechemical structures of the final TiO₂ thin films samples.The V-doped TiO₂ thin films were prepared by TiOSO₄·nH2O and NH4VO3 asraw materials via sol-gel methods. It was found that the grain shape of the TiO₂ filmschanged from spindle shape to sphere-like shape with the increase of V doping. Theanatase-to-rutile transformation was accelerated by the presence of vanadium doping.The 10 mol% V-doped TiO₂ films with a mixed phase of anatase and rutile exhibitedbetter visible light photocatalytic performance. In order to promote the separation rateof photoinduced electrons and holes, the noble metals such as Ag, Pd and Pt weredeposited on the surface of TiO₂ films. Compared with pure TiO₂ thin films, Ag/TiO₂and Pd/TiO₂ exhibited better visible photocatalytic activity. In order to furtherenhance the photocatalytic activity of TiO₂ films, the noble metal and V TiO₂ thinfilms were employed, the Ag/10V-TiO₂ thin films exhibited the best photocatalyticactivity and the degradation rate of methyl orange reach to 76.7% after 6 h visiblelight irradiation. the effect mechanism to visible light response was proposed in termsof impurity energy level and mixed phase structure.In order to enhance the hydrophilicity of TiO₂ thin films, polyethyleneglycol（PEG） and SiO₂ sol were added into TiO₂ sol. It was found that the contact angles ofPEG-TiO₂ and SiO₂/TiO₂ composite films were obviously decreased compared withthe pure TiO₂ thin films. There were abundance hydroxide radicals in PEG and SiO₂sol system which is beneficial for TiO₂ to absorb chemical absorption water andenhance the hydrophilicity of TiO₂ thin films. SiO₂ could inhibit the grain growth andincrease the specific surface area of TiO₂ thin films, thus the photocatalytic activitywas enhanced by adding a small amount of SiO₂. But the crystallinity might becomeworse when the content of SiO₂ was excessive, as a result the photocatalytic activity decreased. In order to further enhance the visible light photocatalytic activity andhydrophilicity of SiO₂/TiO₂ composite films, the vanadium was doped into SiO₂/TiO₂.Compared with the SiO₂/TiO₂ and V-TiO₂ samples, the visible light photocatalyticactivity and hydrophilicity of V-SiO₂/TiO₂ composite films were both enhancedlargely.