Preparation Of Pt-Cr Co-doped Nano-TiO₂ Films And Study On Its Photocatalytic Properties

The utilization of solar energy and the control of environmental pollution are two key objects that must be solved urgently. TiO₂ photocatalysis is widely used in the degradation of the organic pollutants, self-cleaning, sterilization, photoelectric coversion, and so on. Since the bandgap of TiO₂ in the anatase crystalline is comparatively wider(E≈3.2eV), the photocatalytic activities of TiO₂ only effectively work under ultraviolet light irradiation, which accounts for only a small part (3%～5%) of solar energy. In the field of TiO₂ photocatalysis, Therefore, it has become a crucial issue to effectively make use of solar energy by adorning or modification of TiO₂,which resulting in responding of TiO₂ to the range of visible light.Pt,Cr separately doped and Pt-Cr co-doped nano-TiO₂ films were deposited on the slides by sol-gel technique, using tetrabutyl titanate as a precursor in the experiment. Experiment results showed that hydrolysis and condensation velocity could be controlled and sol with good filming property was prepared by changing the matching of water, catalyzer, precursor and solvent etc in solution. The optimal molration is water:diethanolamine:ethanol:nitric acid:tetrabutyl titanate =1:1:35:0.3:1.Optimal hydrolysis temperature is 30℃and optimal annealing temperature and time is separately 450℃and 1 hour. Cr-doped and Pt-doped thin films, Pt-Cr co-doped Nano-TiO₂ films are prepared by adjusting the content of Pt,Cr in the sol. The photocatalytic properties of these fims were characterized by the decomposition rate of methylene blue.The components, microstructure, absorption spectra, thickness and surface topography of the films were analysised via XRD, UV-Vis, XPS, ellipsometric examination and AFM. Experiment results show that When the optimal co-doping ratio is n(Cr:TiO₂) =0.4%, n(Pt:TiO₂) =0.03% , the photodegradation of methylene blue for TiO₂ film can be enhanced. Pt-Cr co-doped Nano-TiO₂ film is anatase; the average diameter of particles is 32nm and the thickness threshold of the film is 290nm, at which, the rate of photodegradation is up to 95% in 2.5 hours. When the thickness is over threshold of the film, the rate of photodegradation becomes stable. The photocatalytic properties of Pt-Cr co-doped Nano-TiO₂ film is better than that of pure TiO₂ and Pt, Cr separately doped TiO₂ film.