Sensitization of photocatalytic activity of S- or N-doped TiO2 particles by adsorbing Fe3+ cations

A new method to dope Fe3+ ions only onto the surface of S- or N-doped TiO2 is proposed. The photocatalytic activities of Fe3+ ions adsorbed on S- or N-doped TiO2 photocatalysts for oxidation of 2-propanol are markedly improved compared to those of S- or N-doped TiO2 without treatment of Fe3+ ions under a wide range of incident light wavelengths, including UV light and visible light. When the amount of Fe3+ ions adsorbed on S-doped TiO2 particles was 0.90 wt.%, photocatalytic activity reached maximum. In the case of N-doped TiO2 with Fe3+ ions, the optimum amount of Fe3+ ions was 0.36 wt.%. The photocatalytic activities of Fe3+ ions adsorbed on S- or N-doped TiO2 photocatalysts decreased gradually when the amount of Fe3+ ions was greater than 1.0 wt.%. In addition, when S- or N-doped TiO2 photocatalysts adsorbed with Fe 31 ions was observed after reduction by NaBH4 followed by air oxidation, further improvement in their photocatalytic activities were observed. In this case, the optimum amounts of Fe3+ adsorbed on the surfaces of S- and N-doped TiO2 photocatalysts were 2.81 and 0.88 wt.%, respectively. During the treatment, Fe3+ ions adsorbed on S- or N-doped TiO2 were reduced to generate metal Fe, and Fe was reoxidized again to form Fe3+ ions under an aerated condition. After the treatment, the crystal structure of Fe3+ ions adsorbed on S-doped TiO2 and adsorbtivity of 2-propanol on the photocatalyst were changed. (c) 2005 Elsevier B.V. All rights reserved.