Preparation of porous metal-ion-doped titanium dioxide and the photocatalytic degradation of 4-chlorophenol under visible light irradiation

Aim: ing at developing a highly active photocatalyst to decompose organic compounds under visible light irradiation, we have prepared metal ion doped TiO₂ (M-TiO₂) by conducting dialysis in sol-gel method. Dialysis leads to the formation of mesoporous materials with surface area larger than 200m²g^-1 but the metal ions should be added into the TiO₂ sol at pH 3 in order to avoid their losses during dialysis. Among seven metal ions tested as dopants, Pt-TiO₂ and Cr-TiO₂ showed higher photocatalytic activity for the degradation of 4-chlorophenol under visible light irradiation. The photocatalytic activity of Cr-TiO₂ was strongly affected by the doping amount of Cr ion and the optimal value was evaluated to be 0.68-1.30atom%. X-ray photoelectron spectroscopy analyses showed the Cr ion was present mainly in Cr(III). The Cr-TiO₂ can be used safely for a practical application to remediate environmental contamination instead of expensive Pt-TiO₂.