Preparation of TiO_2 photocatalysts doped with transition metal ions by adsorption phase synthesis

TiO2 photocatalysts doped with different transition metal ions were prepared via adsorption phase synthesis.Then,photodegradation experiments of methyl-orange were employed to evaluate the influence of different metal ions and ion quantities on the morphology and 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 results 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 of 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 in low quantities influenced little on the activity of photocatalysts.The activity of photocatalysts was obviously depressed after doping by Co2+ in large quantities,since the photo-induced carriers would annihilate easily.