The Study Of The Photocatalytic Activity Of The Doped And Modified TiO₂ Thin Film

Nano-TiO₂ thin film is an important green material with broad band gap, which has the strong adsorption of pollutants, high photocatalytic efficiency, can catalyze a variety of pollutants, nontoxic, and could reduce secondary pollution. Nano-titanium thin fim is attracting the people's growing concern in wastewater treatment, air purification, and it will have potential applications in many other fields.In this study, TiO₂ thin film was prepared by sol-gel method with tetrabutyl titanate as titanium source, anhydrous alcohol as solvent and the glacial acetic acid as inhibitor. Factors affecting the stability of TiO₂ sol such as the amount of water and acetic acid were studied and factors influencing of the photocatalytic activities of TiO₂ thin film such as heat treatment temperature, the thickness of films and pH value were discussed.The properties like crystallographic forms, particles size, and morphology were characterized by the testing techniques such as XRD, TEM, FESEM and UV-Vis absorption spectra. Meanwhile, the variation of particle diameter and crystal phase and the photocatalytic activity of TiO₂ thin film in the process of calcination were researched, and the photocatalytic activity under ultra-violet light was evaluated by photocatalytic degradation of methyl blue.To further enhance photocatalytic activity of TiO₂ thin film, in this paper, the first use of two kinds of Er-Ce and La-Fe co-doping were made to modify TiO₂ thin film by Sol-gel method.The photocatalytic activity under ultra-violet light was evaluated by photocatalytic degradation of methyl blue to determine the best ratio of co-doping and to study the effect of ion co-doping on the photocatalytic activity of TiO₂ thin film. Preliminary study of metal ion doping on the photocatalytic activity of TiO₂ thin film mechanism was studied. The impact of the various mental ions on crystal structure and grain size of the doped TiO₂ thin film was inspected.The results showed that the optimum heat treatment temperature of co-doped TiO₂ was at 550℃and the co-doped TiO₂ kept anatase. The anatase crystal had the average size of 20 nm.The co-doping caused red-shift of the UV-Vis absorption spectra and enhanced the absorption of light. Optimal co-doping amount for Er³⁺-Ce³⁺ was n(Er³⁺): n(TiO₂)=0.1%, n(Ce³⁺): (TiO₂)=0.05% and La³⁺-Fe³⁺ was n(La³⁺): n(TiO₂)=0.05%, n(Fe³⁺): (TiO₂)=0.5%.Under the condition the photocatalysis properties of TiO₂ thin film can be enhanced. It was found that the catalytic activity correlated well with the ratio. The degradation rate of methyl blue examined at two hours of the reaction was 83.75%. The photocatalysis properties of Er-Ce co-doped TiO₂ thin film is quite better than La-Fe co-doped the pure TiO₂ thin film because co-doping elements Er-Ce play a good synergistic effect to promote the improvement of its photocatalytic activity. The co-doped TiO₂ thin film on methyl blue degradation follows the apparent first-order kinetics. The photocatalytic activity results showed that the rare-earth ions were co-doped into TiO₂ thin films, which made the grains smaller, led to aberrance of the crystals and absorbed more -OH. All these changes can increase the specific area of the films, active sites and·H, so the photocatalytic activities of the TiO₂ films can be improved.