Preparation And Photocatalytic Study On Amorphous TiO₂-Cr(V) Thin Films

Titanium dioxide is one of the most popular and promising material as photocatalyst for air treatment and detoxification of waste water. However, nearly all photocatalysic studies on TiO₂ have focused on its crystalline forms, as it is commonly accepted that amorphous TiO₂ has a rapid electron-hole recombination. Nevertheless, crystalloid TiO₂ puts high demand upon preparation temperature and the nature of the substrate. Meanwhile, Titanium dioxide is a semi-conductor with wide band gap, and its photocatalysis operates only when it is irradiated under the ultraviolet radiation of sunlight. Impurity doping of TiO₂ with metal ions can extend light absorption of TiO₂ fairly to the visible region. So, in this paper, we will study the amorphous meatal doped TiO₂ film to improve its photocatalytic activity.In this dissertation, the basic principle about semiconductor photocatalysis was reviewed briefly at first. The methods, research progress and main problems about improving the total quantum-effciency and utilization efficiency of solar energy for semiconductor photocatalysis have been summarized, thedisadvantages and the developing trends about the preparation route of nanosized crystalline TiO₂. Then, a series of TiO₂-M(M is Cr or V)films were prepared at room temperature by reactive magnetron sputtering.The films were investigated by atom microscope, X-ray diffractometer, X-ray photoelectron spectroscopy, UV-Vis spectrophotometer, the photoluminescence (PL) and ellipse polarization apparatus. The photocatalytic properties of these fims were characterized by the decomposition rate of methylene blue or rhodamine B. The effect of doping sputtering power, film thickness, sputtering temperature and the content of adscititious oxidant such as H2O2 and pH value in aqueous Rhodamine B were discussed. And the influence of amorphous metal doped TiO₂ film's photocatalytic activity was principally investigated.The results indicated that TiO₂-M film exists in the form of amorphous. It possessed a band gap of less than 3.20eV, and an appropriate doping imported a new absorption peak. The facts suggest that M-doped (M is Cr or V)results in a great increase in the photocatalytic activity of amorphous TiO₂ films.The probable reason may be that an appropriate chrome doping quantity can led to a rapid increase of photoconduction. The experiments of decomposing methylene blue and Rhodamine B with the films show that the films exhibited excellent photocatalytic activities. As a result, the thickness threshold on TiO₂-Cr film is 114 nm, While, TiO₂-V film is 129 nm, when the thickness is over this numerical number, the rate of photodegradation becomes stable.