| Degradation of organic pollutants by semiconductor photocatalyst is an importantmethod to treat the environmental issues. Among various metal oxide semiconductorphotocatalysts, titanium dioxide （TiO2） is the most preferable material because of itsstrong oxidizing power, nontoxic, and long-term photostability. On the other hand, sinceTiO2for photocatalysis is most commonly processed as powders, the catalyst wouldinevitably encounter an obstacle when applied in practice, that is, the powderphotocatalyst itself could repollute the decontaminated water and air because of thedifficulties in recovery. Furthermore, the powder TiO2photocatalysts also show lowphotocatalytic efficiency due to its easy aggregation behavior. Therefore, thedevelopment of two-dimensional TiO2film photocatalyst with efficient electron–holeutilization and favorable recycling characteristics is important for practical applications.The TiO2film photocatalysts have been prepared by different methods, among thesemethods, radio frequency （RF） magnetron sputtering method provides more advantagesin controlling the structure and composition of the TiO2films, and its easiness to adjust todeposition conditions. Specially, the sputtering method has much flexibility of depositingfilms on differently shaped and sized substrates and can be extended to a large scale.However, the performance of the magnetron sputtered TiO2films needs to be furtherenhanced due in part to its narrow light-response spectrum range as well as its lowquantum efficiency. During the past years, many efforts have been focused on the studyof photocatalytic activity of TiO2sputtered films by doping or coating with metals. Inthis treatise, we mainly studied the photocatalysis of metal-TiO2multilayer films. Threesections are mainly included as following:（1） Fabrication of TiO2films and study of the TiO2films photocatalytic activityWe chose Ti and ceramicTiO2target and prepared by RF magnetron sputtering method. The as-prepared films were characterized by X-ray diffraction, atmoc forcemicrisope. The photocatalytic activity of the samples was evaluated by the photocatalyticdecolorization of methyl blue （MB） aqueous solution under ultraviolet light irradiation.Our results showed that the structure and the photocatalytic activity of TiO2films can beinfluenced by the O2/（Ar+O2）atmosphere, sputtering air pressure, sputtering power andannealing temperature. According to the crystallinity and the photocatalytic activity ofTiO2films, we obtained the best deposition conditions of TiO2films. In subsequentresearch, these experiment parameters were used to fabricate the TiO2films.（2） Fabrication of Pt/TiO2multilayer films and study of their photocatalytic activity.Pt/TiO2multilayered films were prepared by RF magnetron sputtering method. Theas-prepared films were characterized by X-ray diffraction, scanning electron microscopy,atomic force microscope, UV-visible diffuse reflectance spectroscopy, andphotoluminescence spectroscopy. The photocatalytic activity of the samples wasevaluated by the photocatalytic decolorization of methyl blue （MB） aqueous solutionunder ultraviolet light irradiation. The photocatalytic activities of all multilayer filmswere higher than that of the pure TiO2films. The positions of Pt in TiO2film haddifferent effect on the photocatalytic activities of multilayer films. Our results showedthat when Pt layers were situated in middle bottom of TiO2films, the multilayer filmshad better photocatalytic activities. Here, in consideration of adhesive properties of Ptlayers, we prepared five thicknesses of Pt layers situated in middle of TiO2films（TiO2/Pt/TiO2, TPT films）. When Pt thickness was increased to3nm, the measuredphotocatalytic activity of the TPT films was highest, and exceeded that of the pure TiO2films by a factor of more than three times. Such enhancement was ascribed to thepresence of Pt layer, which inhibits the photogenerated charge carriers’ recombination,and modifies the surface roughness and crystallinity of the TiO2up layer.（3） Fabrication of Au/TiO2multilayer films and study of their photocurrent activity.Au/TiO2multilayer films were prepared by RF magnetron sputtering method. Westudied the effect of annealing process on morphology and absorption properties of Au layers. At the same time, the photocurrent of samples was also discussed in this section.Our results showed that the Au particles on the surface of Au films agglomerated duringannealing process, and then the surface plasmon（SP） resonance of Au particles could befound. In addition, the photocurrent of Au/TiO2multilayers was higher than pure TiO2films under UV and visible light. Under UV light, Au layers in the multilayer films canproduce a Schottky barrier, which facilitate the electron capture. Under visible light, Aulayers act as electron donor because of the SP resonance. These electrons can effectivelyinject to TiO2films, so as to the increase of photocurrent of multilayer films. |
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