Study Of The Controllable Preparation And Performance Of The Columnar Structured Tio₂:F/Fto Composite Films

With the aggravation of environmental pollution, the problem of cleaning the architectural energy-saving glass has aroused people’s wide attentions. Lots of studies have focused on the architectural energy-saving glass with self-cleaning function in the field of building energy-saving. It will reach the self-cleaning purpose if the surface is coated with the materials that can degrade the organic pollutants. Among the self-cleaning materials, TiO2has been extensively studied due to its chemical stability, non-toxicity, low cost, high photocatalytic activity and super hydrophilicity. However, the high recombination of the photo-generated carriers leads to the poor photocatalytic activity for TiO2films. Therefore, in the premise of ensuring low-emissivity (low-e) and transmittance properties of architectural glass, it is a key point to improve the photocatalytic activity of TiO2films.Doping elements and film morphology play a decisive role to improve the photocatalytic activity of TiO2films. Doping F element can effectively enhance the crystallization of TiO2films and reduce the recombination of photo-generated electron-hole pairs. Meanwhile, compared to granular morphology with the poor crystallization and loose structure, the columnar morphology can contribute to improving the photocatalytic activity of TiO2films due to its low density of grain boundaries and high migration rate of the photo-generated carriers.In view of the above considerations, this paper have used the Sol-gel multiple spin-coating method to successfully prepare the columnar structured TiO2films on the quartz substrates. The single layer thickness (SLT) of the columnar structured TiO2films is25～30nm, which increases2～3times than the reported needed thickness (～10nm). On this basis, the columnar structured TiO2:F films were successfully prepared on the SnO2:F films (FTO) substrate. The effects of F doping ratio and TiO2:F film thickness on the photocatalytic, low-e and transmittance properties have been investigated in detail.The columnar structured TiO2:F/FTO composite films are mainly composed of anatase TiO2and rutile SnO2without rutile TiO2or the other phases. It is much easier to prepare the columnar structured TiO2films on the FTO substrate than the quartz substrate, the SLT can reach about28～30nm. The photocatalytic activity of the columnar structured TiO2:F/FTO composite films is enhanced with the increase of the F doping ratio and TiO2:F film thickness, and then decrease when F doping ratio and TiO2:F film thickness are too large, the optimum F doping ratio and TiO2:F film thickness are respectively4%and320nm. The low-e properties of the columnar structured TiO2:F/FTO composite films are not affected by F doping ratio, but decrease with the increase of the TiO2:F film thickness. However, the hemispherical emissivity is still less than0.25, which satisfies the requirements of building energy-saving glass. The F doping ratio and TiO2:F film thickness have no great effect on transmittance of columnar structured TiO2:F/FTO composite films, the average transmittance is about70%, meeting the lighting requirements of the architectural glass.