Preparation Of TiO₂ Columnar Structure Film, And Research Of The Properties And Mechanism Of FTO/TiO₂ Composite Films

In this paper, columnar crystalline structured TiO2 films were obtained on the FTO substrate via an improved sol-gel method. The experimental processing parameters, such as annealing temperature, the number of spin-coating times and their influences on the structures, morphology and properties of the FTO/TiO2 composite films were investigated respectively. Spherical crystalline structured TiO2 films were prepared in order to investigate the impact of different crystalline structures on the structures, morphology and properties of FTO/TiO2 composite films. Results showed that the crystalline structures of TiO2 composite films remain the same. The composite films annealing under 550℃consist of rutile SnO2 and anatase TiO2 both with perfect crystalline structure. The surface of the spherical structured composite films was spherical and the surface of the columnar structured composite films was sharp needle. The later is smoother than the former. The columnar structured composite films showed a better photocatalytic performance than the spherical structured composite films. The photocatalytic activity of the two different crystal morphology of the composite films increased and then decreased with the increase in thickness of TiO2 layer. Columnar crystal structured composite films have lower low-emissivity and better visible light transmitting property than the spherical crystal composite films. In this paper, we propose a possible mechanism to explain the impact of different crystal structure on the various properties of the composite films. We also give a photocatalytic enhancement mechanism for the FTO/TiO2 heterojunction from the perspective of band theory.