碱/酸两步催化法制备的“核-壳”SiO2-TiO2纳米材料及其光催化特性

Preparation and photocatalytic property of “core-shell” SiO_2-TiO_2 nano material by base/acid two-step sol-gel process

以正硅酸乙酯(TEOS)为前驱体,以氨水为催化剂,制得含有SiO_2粒子的碱催化SiO_2溶胶;向碱催化SiO_2溶胶中加入前驱体钛酸丁酯(TBOT)和酸催化剂盐酸,得到以SiO_2粒子为核和以TiO_2为壳的"核—壳"SiO_2-TiO_2纳米材料.结果表明:SiO_2核的粒径约为13.5 nm;随着钛酸丁酯添加量的增加,SiO_2核表面不断有TiO_2壳形成,其粒径从13.5 nm增大至24.4 nm.XRD测定结果表明煅烧温度为500℃时,锐钛矿TiO_2的特征衍射峰明显增强.该温度下"核—壳"SiO_2-TiO_2复合粉末对罗丹明B的降解率从21.99%提高到94.86%.

In order to improve the photocatalysis of SiO_2-TiO_2 with increased specific surface area,a base / acid two-step process was adopted to manufacture a'core-shell'structure. The base-catalyzed SiO_2 sol containing SiO_2 particles was prepared by using tetraethyl orthosilicate( TEOS) as precursor and ammonia as catalyst. Then butyl titanate( TBOT) and hydrochloric acid were added to the resultant SiO_2 sol to obtain SiO_2-TiO_2 composite with the 'core-shell'structure,with SiO_2 particles being the core and TiO_2 as the shell. Subsequent diffraction after calcination and rhodamine B degradation were measured to verify the photocatalic activity of the composites. Results showed that particle size of SiO_2-TiO_2 composites increased gradually from 13. 5 nm( SiO_2 particle size only) to 24. 4 nm with the addition of butyl titanate,indicating forming the'shell'TiO_2 on the surface of silica particles. X-ray diffraction( XRD) results implied that the characteristic diffraction peak of anatase TiO_2 enhanced significantly when being calcined at500 ℃. Degradation rate of rhodamine B increased from 21. 99% to 94. 86% when TiO_2 content decreased,indicating increased photocatalysis SiO_2-TiO_2. To summarize,photocatalytic activity of the SiO_2-TiO_2 composite increased compared with pure TiO_2.