N-TiO2/ZnO复合纳米管阵列的掺杂机理及其光催化活性

以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高.

Doping Mechanism of N-TiO2/ZnO Composite Nanotube Arrays and Their Photocatalytic Activity

TiO2/ZnO and N-doped TiO2/ZnO composite nanotube arrays were synthesized by the sol-gel method using ZnOnanorod arrays as a template. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance UV-Vis spectroscopy (UV-Vis) were used to characterize the samples. The nanotubes had a uniform hexagonal shape. The diameter and wall thickness of the nanotubes were about 100 nm and 20 nm, respectively. Some N dopants were substitutionally doped into the TiO2 lattice, while the N-Ox, N-C, and N-N were chemically absorbed onto the surface of the TiO2/ZnO composite nanotubes. Dopant-induced narrowing of the bandgap resulted from the doping of N ions into the TiO2 lattices. The surface N species enhanced the visible-light response and promoted the separation of photogenerated carriers. Compared with the TiO2/ZnO composite nanotube arrays, the N-TiO2/ZnO composite nanotube arrays exhibited higher photocatalytic activity.