Abstract

Transition metal (vanadium, chromium, iron) doped TiO₂ was synthesised by co-precipitation or by surface-deposition. The specimens were characterised by XRD and reflectance spectroscopy. In terms of the structure, the surface doped samples are same as those made by co-precipitation nor did the presence of metal ions change the structure. The presence of transition metal induced a shift of light absorption of the doped TiO₂ to visible wavelengths. The introduction of transition metal ions into TiO₂ significantly affected the photoactivity, which was determined by the oxidation of IPA and photogreying. As a general trend, an optimum dopant appeared which gave the maximum photoactivity. It was found that the photoactivity of co-precipitated samples was lower than that of surface-doped. The photoactivity of doped TiO₂ is a function of many parameters, such as the dopant content, energy level of dopant, the d electronic configuration of dopant ions and the distribution of dopant. These factors influence IPA photo-oxidation and photogreying to different extents.

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