Transition Metal - Doped Tio ₂ Study On Hydrophilic And Photocatalytic Properties Of Thin Films

In this paper, TiO₂ was doped to enhance photocatalytic activity and hydrophilicity. TiO₂ films and Ni²⁺, Fe³⁺ and Cu²⁺ doped TiO₂ multilayers were grown by sol-gel on glass substrates were characterized with X-ray diffraction (XRD), atomic force microscopy (AFM) and water contact angle measurement. By means of many advanced experiments, the microcosmic mechanism of photocatalytic process was studied in order to find basic factors that affect photocatalytic efficiency and provide theoretical basis of designing and preparing high efficient photocatalys.We investigated systematically the effect of transition metal ions doping TiO₂ on its activity of hydrophilicity production. The high active hydrophilic of transition metal ions doping TiO₂ had been prepared by sol-gel method.Among all the doped samples, TiO₂ doped with Ni²⁺photocatalyst has the best hydrophilicity activity. When the doped molar content of Ni²⁺ was 2m01%, the calcinated temperature was 500℃and the calcinated time was 2h, the contact angles of Ni²⁺ doping TiO₂ can keep hydropilicity after storage in dark for 7 days. The sample of Ni²⁺ doping TiO₂ also had excellent photo-induced superhydrophilicity. After under UV irradiation for 2h, the contact angles were reduced to 0°, the hydropilicity activity of Ni²⁺ doped TiO₂ was well repaired, the TiO₂ photocatalyst poisoning problem has been well solved. The analysis of structure indicated that transition metal ions doping in TiO₂ didn't influence the crystal paterns of TiO₂ particle, the crystal transformation of TiO₂ from anatase to rutile was prevented, the particle diameter decreased and the hydroplicity of TiO₂ was increased. The hydrophilicity of TiO₂ films was little affected by Cu²⁺ doping and Fe³⁺ doping.We investigated systematically the effect of transition metal ions doping TiO₂ on its activity of photocatalytic production. The high active photocatalyst of transition metal ions doping TiO₂ had been prepared by sol-gel method. Among all the doped samples, TiO₂ doped with Cu²⁺ photocatalyst has the highest activity, Fe³⁺ doping caused little affect on photocatalytic activity and Ni²⁺ doping even caused a decrease in the photocatalytic activity. When the doped molar content of Cu²⁺ was 3mol%, the calcinated temperature was 500℃and the calcinated time was 2h, the photocatalytic activity of Cu²⁺ doping TiO₂ after UV light irradiating for lh had increased from pure TiO₂ 40% to 54%. The analysis of structure indicated that transition metal ions doping in TiO₂ didn't influence the crystal paterns of TiO₂ particle, but Ni²⁺, Cu²⁺or Fe³⁺ doping produced latice deformation which caused the change of the electron density in TiO₂, and then influcenced the hydroplicity and photocatalytic of TiO₂. We researched the doping mechanism of TiO₂. It was found that the photocatalytic activities depend on the size and location of the doping ions in TiO₂. When the radii of doping ions were smaller than that of Ti⁴⁺ or closer to the Ti⁴⁺, the doping effect was obvious; while the radii of doping ions were much larger than that of Ti⁴⁺, the doping effect was lower. The doped TiO₂ photocatalytica ctivities were in the order: Cu²⁺＞Fe³⁺＞Ni²⁺. This result is very important to realize the essence of photocatalysis.