Preparation And Photocatalytic Properties Of Tio₂-n Films On Different Substrates

Titanium dioxide, widely used in the degradation of organic pollutants in the gas and aqueous solution, is a representative photocatalyst of n-type semiconductor oxide. And it has been one of the hot worldwide researches.In the study, the N doped TiO2 thin films on different substrates were prepared by sol-gel dip-coating method, and some typical wastewater as the study object was leading research direction. The results showed that the catalyst were highly responsive to the visible light. The main contents and conclusions were presented as follows:(1) The urea was used as the source of nitrogen. Measured by SEM, the N doped TiO2 which used the urea as the source of nitrogen showed the good crystallinity, uniform and large surface area. And it showed good photocatalytic activity, too. The single factor experiments and orthogonal experiment showed that, the layers is the most important factor on the photocatalytic activity, followed by the acetyl acetone and the temperature. The optimum conditions of the N doped TiO2 thin films were: ethanol: water: nitric acid: acetyl acetone: butyl titanate= 40:0.8:0.25:0.2:1; six layers and the calcination temperature was 525℃.(2) The different substrates showed varying degrees in the combination with the N doped TiO2 thin films. The conductive glass and ordinary glass had the good combination, and they changed little in the re-use reaction. The substrate copper easily fell off from the N doped TiO2 thin films. The substrate iron occurred the corrosion during the degradation, and showed worse in the re-use reaction. The coating of aluminium was uneven. In the degradation of reactive brilliant red under the visible light, the substrate iron showed the highest rate, followed by copper, ordinary glass, aluminium and conductive glass. In the degradation of chlorophenol solution under the visible light, the substrate copper showed the highest rate, followed by ordinary glass, conductive glass, iron and aluminium. So the ordinary glass would be the best substrates.(3) With the N doped TiO2 thin films on different substrates as photocatalyst, we tested hydroxyl radical by Fluorescence spectroscopy, which can conclude the catalyst could produce the hydroxyl radical with the visible light, the longer the time, the more amount of .OH could be tested, and the .OH can degrade the organic matter. Among them, the iron catalyst for the substrate film output up to ? OH, conductive glass substrate thin film catalyst to produce the least amount of ? OH.(4) The photocatalytic activity of TiO2 can be improved by codoping with copper and nitrogen. In the repeat experiment, all the thin film catalyst(pure TiO2 thin film, N doped TiO2 thin film, Cu(0.01%,0.05%,0.1%)doped TiO2 thin film and N-Cu (0.01%,0.05%,0.1%) codoped TiO2 thin film) showed best in the first degradation. The best degradation rate was 76.6% by N-Cu (0.01%) codoped TiO2 thin film, and the lowest degradation rate was 23.3% by the pure TiO2 thin film. In the forth time, the degradation rate of N-Cu (0.01%) codoped TiO2 thin film was down to 56.6%, and the pure TiO2 thin film was to 10%.