采用溶胶-凝胶浸渍提拉法在不同玻璃基板上制备TiO_2薄膜,并通过降解浸渍在薄膜表面的甲基蓝来评价其光催化活性.利用X射线衍射(XRD)、X射线光电子能谱(XPS)和紫外-可见(UV-Vis)吸收光谱等研究了晶型、表面元素分析和光吸收性能.并采用平行电极法测定TiO_2薄膜的光电流,研究了薄膜表面载流子的复合情况.结果表明,薄膜的催化性能主要与基板热扩散到薄膜中的Na~+和晶相相关.Na~+抑制锐钛矿相TiO_2的形成,并且在一定条件下促进由锐钛矿向金红石相的转变.Na~+的扩散对TiO_2晶粒尺寸影响不大.重要的是,扩散至薄膜的Na~+不仅影响TiO_2薄膜的晶相转变,而且成为光生电子与空穴的复合中心,同时影响其光催化活性.
TiO_2 thin films were prepared by sol-gel dip-coated method on various kinds of glass substrates.Photocatalytic activities were evaluated by photocatalytic degradation of methylene blue adsorbed on different TiO_2 thin films.Crystalline phase,surface elemental analysis and optical absorption property were studied by XRD,XPS and UV-Vis technologies,respectively.The recombination situation of surface carriers was also studied by determinating the parallel electrode photocurrent of TiO_2 films.The results showed photocatalytic activities of the thin films were mainly related to the crystalline phase and sodium ions diffused from substrates into the films.Sodium ions restrained the formation of anatase TiO_2,and were able to promote the conversion from anatase to rutile phase under certain conditions.Diffusion of sodium ions had little effect on the particle size of TiO_2.Substantially,sodium ions diffused in the film not only had an important effects on the structural conversion of TiO_2 thin films,but also became the recombination centers of photo-electrons and holes,moreover they will influence the photocatalytic activity.
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