La／TiO_2-SiO_2薄膜的光催化性能研究

Photocatalysis of La/TiO_2-SiO_2 Thin Films

采用溶胶-凝胶法制备了不同掺杂量的La／TiO2-SiO2复合薄膜．通过XRD、 FE-SEM和AFM研究了复合薄膜的微观结构,采用紫外光照射下亚甲基蓝的分解实验比较薄膜的光催化性能．结果表明:La掺杂可显著提高TiO2-SiO2复合薄膜的光催化活性,以5％掺杂量为最佳,其光降解率比掺杂前提高了约23％．薄膜活性提高的主要原因是La掺杂后细化了TiO2的晶粒,提高了薄膜的比表面积,使其具有更高的氧化还原电势,La2+取代Ti4+ 进入到TiO2晶格,引起晶格膨胀,这种不同价离子的取代导致TiO2粒子表面电荷分布不平衡,从而提高了光生电子-空穴的分离效率．

La/TiO2-SiO2 thin films were prepared by sol-gel processing. The photocatalysis of the films was characterized by means of photocatalytic degradation of methylene blue under UV irradiation. The microstructures of prepared films were characterized by using XRD, FE-SEM and AFM analysis. The results show that La^3＋ doping can significantly improve the photocatalysis of the composite film. The best proper La doping content is 5%, and the degradation rate of La/TiO2-SiO2 is increased by 23%, higher than that before La doping. The main reason is that La^3＋ makes TiO2 grain size smaller, which leads to the increase of the specific area of TiO2, resulting in the higher oxidation-reduction potential of the film. Meanwhile cation vancacies with negative charge are generated when some La^3＋ replace Ti^4＋, which makes TiO2 surface charge out of the balance, and raises separation efficiency of photoelectron-hole pairs, thus improving the photocatalysis of the composite film.