The Fabrication Of TiO₂-CdS Films System And Photocatalysis Under Single/Double Beam Lights Induced By Photoelectric Synergistic Effect

TiO₂ has become a research hotspot worldwidely due to its potential applications in future. However, only the ultraviolet light in solar spectrum can be used owing to its wide bandgap energy. Furthermore, the quantum yield is very difficult to be further increased because of the rapid recombination of the photogenerated electrons and holes before interface transferring. Those intrinsic drawbacks have limited the progress of the photocatalytic researches. Aiming at those problems, we have mainly studied the following contents.(1) Anatase TiO₂ nanocrystalline thin films were prepared by reactive magnetron sputtering and characterized by UV-Vis, XRD, SEM, FE-SEM and Raman techniques. It was found that a well-crystallized, uniform and smooth TiO₂ thin film can be prepared at the substrate temperature of 290℃with the～30 nm grain size and 3.21 eV bandgap energy.(2) CdS nanocrystalline thin films were prepared using chemical bath deposition (CBD) and characterized by UV-Vis, XRD, SEM, FE-SEM and Raman techniques. These results shows that, the CdS thin film prepared at the conditions of the bath temperature of 80℃, pH value of 10, deposition time of 120 min and Cd-S ration of 2:25 are well-crystallized, uniform, and smooth, and the average grain size is～30 nm.(3) Using the self-designed photoelectrocatalysis reaction cell, we compared the efficiency of photocatalysis and photoelectrocatalysis with TiO₂ or CdS films and TiO₂-CdS film system under irradiation of UV or visible light and UV+visible two beam lights. The photocatalysis and photoelectrocatalysis were studied in detailed in the cases of single and double beam lights illumination under and without galvanostatic and potentiostatic conditions, with the TiO₂ film and CdS film using as the working and counter electrodes. The results show that, the efficiencly of photoelectrocatalysis is higher than that of photocatalysis, and the efficiency of the double-beam lights induced photocatalysis (photoelectrocatalysis) of TiO₂ and CdS system is higher than the sum of the single beam light induced photocatalysis (photoelectrocatalysis) of TiO₂ and CdS films. In addition, under the electric field of negative galvanostatic method and positive potentiostatic method, the electrons on TiO₂ can be extracted to the conduction band of CdS film, and the photocatalytic activity increase with increase of the value of current and potential.(4) The TiO₂ and CdS films before and after photoelectrocatalysis course were characterized using XRD, Raman, FE-SEM techniques, respectively. Furthermore, the V-I characteristic and photocatalytic efficiency were also conducted on the TiO₂ film before and after photoelectrocatalysis course. It is obtained that photoelectrocatalysis course can promote the film crystallinity, and the TiO₂ film form a interconnected mesoporous networks after photoelectrocatalysis course. Accordingly, the photocurrent and the photocatalytic ability of the TiO₂ increase nearly two times higher than that of the as-prepared TiO₂ film.