纳米二氧化钛/碳纳米管复合催化剂光催化性能及碳纳米管组分的作用

Photocatalytic Properties and the Role of Carbon Nanotubes in TiO_2/Carbon Nanotube Composites

运用溶胶-凝胶及低温水热法合成纳米TiO2/碳纳米管复合催化剂,以甲基橙为目标降解物考察复合物的光催化活性.运用X光衍射、透射电镜、Brunauer-Emmett-Teller低温氮气吸附、差热-热重分析及紫外-可见漫反射吸收光谱等表征催化剂.结果表明,与单纯纳米TiO2相比,溶胶-凝胶法制备的复合催化剂的光催化活性显著提高,实验条件下复合的碳纳米管最适含量为3%(碳纳米管/TiO2,重量百分比),复合催化剂经在缓和氧化气氛中焙烧处理可在保持碳纳米管热稳定前提下获得纳米TiO2的充分晶化.观察到了低温水热合成的复合催化剂的甲基橙降解活性的进一步提升,复合催化剂中纳米TiO2在碳纳米管表面分散均匀,TiO2和碳纳米管组分间的紧密和充分键合及低温水热条件下催化剂的大比表面积、超细粒径以及碳纳米管的热稳定等有利于复合催化剂的光催化活性.进一步地,探讨了复合催化剂中适量碳纳米管组分的光活性促活机制.

TiO2/carbon nanotube composites were prepared by modified sol-gel and low temperature hydrothermal synthesis.The photocatalytic activity of as-prepared composites was evaluated by the degradation of methyl orange.The samples were characterized using X-ray diffraction,transmission electron microscopy,Brunauer-Emmett-Teller adsorption analysis,thermogravimetric-differential thermal analysis and UV-Vis diffuse reflectance spectroscopy.Enhanced photocatalytic activity was obtained on the composites prepared by sol-gel method and the optimum weight ratio of carbon nanotubes over titanium dioxide in the composites was founded to be 3%.It is found that calcining composites in a moderate oxidative atmosphere allowed the compatibility of sufficient crystallization and well thermal stability of the composites.Further enhancement of photoactivity was observed on TiO2/carbon nanotube composites prepared by hydrothermal synthesis.The carbon nanotubes in the composites were virtually well covered by TiO2.The further enhanced photoactivity can be attributed to the intimate heterojunctions between TiO2 and carbon nanotubes,higher surface area,fine particles and the thermal stability of the composites obtained at the low hydrother-mal temperature employed.The role of appropriate amount of carbon nanotubes in composites for enhanced activities was discussed.