中文摘要：

作为光催化技术的核心,提高TiO2的光催化活性和对可见光的利用率是当前光催化研究中最重要的研究课题.为了提高TiO2纳米管的可见光催化活性,采用化学气相沉积法对TiO2纳米管进行了氟掺杂.扫描电子显微镜（SEM）结果表明退火温度对于TiO2纳米管的形貌完整性有较大影响,当样品在550和700°C下退火,氟掺杂TiO2纳米管结构受损;X射线衍射（XRD）分析表明氟掺杂对TiO2由锐钛矿相转化为金红石相有阻碍作用;X射线光电子能谱（XPS）测试表明化学气相沉积能有效地对TiO2纳米管进行非金属掺杂,且该方法安全、操作简单.氟掺杂TiO2纳米管对甲基橙有较高的可见光催化降解活性.第一性原理计算结果表明氟掺杂对TiO2带隙无显著影响,费米能级附近的F2p轨道电子位于价带底部,与O2p交联作用较小,因此对TiO2光吸收带边影响不大.氟掺杂能促进表面氧空穴的产生,增加表面酸度与Ti3＋,有利于减少电子-空穴复合率,从而提高其光催化活性.

英文摘要：

Improving the photocatalytic activity and the utilization of visible light of TiO2 is the most important research topics in the photocatalytic field. To improve the photocatalytic activity of TiO2, we used chemical vapor deposition （CVD） to dope TiO2 nanotubes with fluorine. Scanning electron microscopy （SEM） images showed that the annealing temperature significantly affected the morphological integrity of TiO2 nanotubes. Upon annealing at 550 and 700 °C, the structure of F-doped TiO2 nanotubes suffered from an observable disintegration of morphological integrity. X-ray diffraction （XRD） results indicated that the F impurity retarded the anatase-rutile phase transition. Fluorine was successfully doped into TiO2 by CVD, as indicated by the X-ray photoelectron spectroscopy （XPS） results. F-doped TiO2 nanotubes showed higher photocatalytic activity. First-principles calculations suggested that the F 2p states were located in the lower-energy range of valence band （VB） and less mixed with O 2p states. It thus contributed little to the reduction of the optical band gap. This is consistent with the finding that the band gap of F-doped TiO2 is very close to that of undoped TiO2. Therefore, the higher catalytic activity of F-doped TiO2 should be attributed to the creation of surface oxygen vacancies upon F-doping, which enhances surface acidity and increases the amount of Ti3＋ ions.