Photocatalytic activities of Ion doped TiO(2) thin films when prepared on different substrates

Pure and ion doped TiO(2) thin films were prepared by sol-gel dip coating process on metallic and nonmetallic substrates. Test metal ion concentration ranged from 0.000002 to 0.4 at.%. The resulting films were annealed in air and characterized by optical spectroscopy and X-ray diffraction. The photodegradation of methyl orange under UV irradiation by pristine and ion-doped TiO(2) films was quantified in a photocatalytic reactor developed in this study. In general, both doped and undoped TiO(2) crystals appeared in anatase phase and the photocatalytic activities of the TiO(2) thin films varied with substrates, calcination temperature, doping ions and their concentrations. The best calcination temperature for different substrates ranged from 450 to 580 degrees C. Films prepared on the metallic substrates resulted in higher photocatalytic activities, while ion doping lowered their efficiencies. On the contrary, for non-metallic substrates except ceramic the photocatalytic efficiencies of undoped films were much lower (<30%), while ion doping was shown to increase the photocatalytic efficiencies remarkably in some cases, e.g., Cr(3+) with the the substrate. Overall, ion doping affected the photocatalytic efficiency of TiO(2) films, and an optimal doping concentration of between 0.0002 and 0.002 at.%, close to an estimate by the Debye length equation, resulted in the highest efficiency for most substrates. (C) 2009 Elsevier B.V. All rights reserved.