The Photocatalytic Activity Research Of Re-Doped TiO₂ Films Under Visible Light

The photocatalytic oxidation technique of TiO2 has been paid more and more attention for the advantage of less cost, mild reaction condition, easy operation and less secondary pollution. However TiO2 may show photocatalytic activity only by irradiation of ultraviolet(UV) light for its wide band gap(Eg=3.2eV). But the proportion of UV light to the sun light is very small. In addition, easy recombination of photo-induced electrons and holes makes the efficiency of photoquantum lower. These unfavorable factors have the photocatalytic oxidation technique of TiO2 limited in practice. Considering the problems above, the idea that TiO2 photocatalyst is doped with rare-earth ions(La3+,Eu3+,Nd3+) is presented to improve the photocatalytic performance of TiO2 and enhance the absorbing wavelength to the visible light wavelength.In this paper, the TiO2 film was prepared by sol-gel method. The effect of the dosage of different ingredients, pH and sintering process on the preparation of sol and film, structure of TiO2 film and photocatalytic performance were studied. The result showed that the optimal parameter of mixture ratio of Ti(OC4H9)4, CH3CH2OH, H2O and nitric acid was 1:3:0.1:0.05. The best number of coating cycles was 5. The photocatalytic activity of different sintering under visible light was studied too. When the sintering temperature was 500℃, the content of anatase TiO2 was high and TiO2 films had considerable photocatalytic activities. In order to get higher photocatalytic performance under visible light, the rare-earth ions were added into the TiO2 sol, and the photocatalytic activity of TiO2 films was studied too. The result showed that photocatalytic property can be improved by adding suitable dosage of rare-earth ions. Nd-doped TiO2 film had the highest photocatalytic property, La-doped TiO2 was inferior, Eu-doped TiO2 was the lowest of all. When the dopant concentration of Nd was 0.9mol%, the photocatalytic remove ratio is 23.9% higher than the pure film without doped. SEM, AFM, XRD and XPS were used to observe and analyze the structure of undoped TiO2 and doped TiO2 films. The results showed that the rare-earth ions were doped into the TiO2 films, which made the grains smaller, led to aberrance of the crystals and absorbed more -OH. All these changes can increase the...