Abstract: TiO2 photocatalysts doped with different metal ions were prepared by adsorption phase synthesis. Then, photodegradation experiments of methyl-orange were employed to evaluate the influence of different metal ions and different ion quantities on the activity of these photocatalysts. The results from TEM and UV-visible spectra showed that metal ions doping affected little the morphology and light absorbance of TiO2. XRD indicated that the replacement of Ti4+ in TiO2 lattice structure by other metal ions restricted the crystallization of TiO2. The restriction on the crystallization became stronger, when ions radius was close to Ti4+ or quantities of doping ions increased. The results in photodegradation experiments suggested that there was an optimum dopant quantities appeared during preparation of TiO2 doped with Cd2+ and Fe3+. Due to various ion radiuses, the optimum dopant quantities of Cd2+ and Fe3+ were also different. Co2+ doping under low quantities influenced little on the activity of photocatalysts. The activity of photocatalysts was obviously depressed after doping by metal ions under high quantities, since the photo-induced carriers would annihilate easily.

Key words: metal ions diping, adsorption phase synthesis, TiO2, crystallization, methyl-orange