Yao Yuan, Li Gonghu, Ciston Shannon, Lueptow Richard M, Gray Kimberly A
Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208, USA.
Environ Sci Technol. 2008 Jul 1;42(13):4952-7. doi: 10.1021/es800191n.
Electron-hole recombination limits the efficiency of TiO2 photocatalysis. We have investigated the efficacy with which anatase/carbon nanotube (CNT) composite materials reduce charge recombination and enhance reactivity. We synthesized nanostructured assemblies composed of different proportions of anatase (5 or 100 nm) and either single-or multi-walled CNTs. The composites were prepared using a simple low temperature process in which CNTs and anatase nanoparticles were dispersed in water, dehydrated at 80 degrees C, and dried at 104 degrees C. The structures of the various TiO2/CNT composites were characterized by scanning electron microscopy (SEM) and their function was tested by phenol oxidation. Charge recombination was compared by measuring the photoluminescence spectra of select composites. We found that a nanostructured composite assembled from the 100 nm anatase and single-walled CNTs (SWCNTs) exhibited enhanced and selective photocatalytic oxidation of phenol in comparison to both pure anatase and Degussa P25. A mechanism for the enhanced reactivity is proposed in which electrons are shuttled from TiO2 particles to the SWCNTs as a result of an optimal TiO2/ CNT arrangement that stabilizes charge separation and reduces charge recombination. In addition, the SWCNT assembly provides better catalyst-support (dispersal and connection) than multi-walled CNTs.
电子-空穴复合限制了二氧化钛光催化的效率。我们研究了锐钛矿/碳纳米管（CNT）复合材料降低电荷复合并提高反应活性的效果。我们合成了由不同比例的锐钛矿（5或100纳米）与单壁或多壁碳纳米管组成的纳米结构组件。这些复合材料采用简单的低温工艺制备，即将碳纳米管和锐钛矿纳米颗粒分散在水中，在80摄氏度下脱水，并在104摄氏度下干燥。通过扫描电子显微镜（SEM）对各种二氧化钛/碳纳米管复合材料的结构进行了表征，并通过苯酚氧化测试了它们的功能。通过测量选定复合材料的光致发光光谱来比较电荷复合情况。我们发现，与纯锐钛矿和德固赛P25相比，由100纳米锐钛矿和单壁碳纳米管（SWCNTs）组装而成的纳米结构复合材料对苯酚表现出增强的选择性光催化氧化作用。提出了一种反应活性增强的机制，即由于优化的二氧化钛/碳纳米管排列使电荷分离稳定并减少电荷复合，电子从二氧化钛颗粒转移到单壁碳纳米管。此外，单壁碳纳米管组件比多壁碳纳米管提供了更好的催化剂载体（分散和连接）。
