缺陷态对TiO2基纳米异质结光催化性能影响机理研究

As a typical representative of excellent photocatalysts, TiO2 has long been of concern. Unfortunately, the large band gap and low quantum efficiency limit the efficient absorption of TiO2 for sunlight and its catalytic performance. In view of these two aspects, the development of heterostructures in recent years can effectively improve the solar light photocatalytic performance of TiO2. For the TiO2-based semiconductor oxide heterostructures, the defect states would affect the photocatalytic performance. However, there is no systematic study being performed on the intrinsic mechanism of it. Therefore, the influence mechanism of the defect states on the photocatalytic performance of TiO2-based nanoheterostructures will be studied here: the influence of the defect state on the energy band structure will be revealed; the intrinsic relationship between the defect state and the light absorption will be studied; the effects of defect states on the separation, transfer and transport of the electron-hole pairs in heterojunctions will also be investigated. As the most important aspect, the separation, transfer and transportation of photogenerated charge in the heterojunctions is the hot and difficult problem in the word. The problem will be studied using time-resolved terahertz spectroscopy with time resolution of sub-picosecond to obtain the clear scientific understanding, and this can provide basis for designing TiO2-based nanoheterostructures with high photocatalytic performance.

TiO2作为优异光催化剂的典型代表，长期以来备受关注。遗憾的是，大的禁带宽度和低的量子效率限制了TiO2对太阳光的高效利用及其催化性能的提升。针对上述两大难题，近年来发展的构筑异质结的方法可有效提高TiO2太阳光催化性能。对于TiO2基异质结氧化物半导体而言，缺陷态对材料的光催化性能会产生重要影响，然而目前关于缺陷态影响异质结光催化性能的内在机理仍缺乏系统研究。基于此，本项目拟围绕TiO2基纳米异质结开展缺陷态对光催化性能影响机理研究：研究缺陷态对材料能带结构的影响；揭示缺陷态与光吸收间的内在联系；获得缺陷态对异质结中电子-空穴对的分离、转移和输运过程的影响规律。其中，光生电荷的分离、转移和输运是研究的关键，也是国内外的研究热点和难点。本项目拟利用具有亚皮秒时间分辨的太赫兹光谱开展相关研究，获得较为清晰的科学认识，为合理设计高性能TiO2基异质结光催化材料提供依据。

TiO2作为优异光催化剂的典型代表，长期以来备受关注。遗憾的是，大的禁带宽度和低的量子效率限制了TiO2对太阳光的高效利用及其催化性能的提升。针对上述两大难题，近年来发展的构筑异质结的方法可有效提高TiO2太阳光催化性能。对于TiO2基异质结氧化物半导体而言，缺陷态对材料的光催化性能会产生重要影响，然而目前关于缺陷态影响异质结光催化性能的内在机理仍缺乏系统研究。基于此，本项目拟围绕TiO2基纳米异质结开展缺陷态对光催化性能影响机理研究。研究发现缺陷态的引入可使半导体带隙变窄，从而使得吸光范围红移至可见光区。项目还利用超快吸收、发光光谱和具有亚皮秒时间分辨的太赫兹光谱研究了缺陷态对光生电荷的分离、转移和输运的影响，结果发现复合材料界面处的界面缺陷会形成深浅不一的捕获陷阱，其对载流子的捕获方式决定了载流子的分离和迁移，捕获中心对单种载流子的捕获有利于电子空穴对的分离和迁移，载流子寿命因此得到提升，因此光催化性能可得到进一步提升；缺陷态对光生电子和空穴的共同捕获会加快载流子的带隙复合进程和缺陷相关的间接复合进程，不利于电子空穴对的分离，载流子寿命因此降低，这对光催化产生消极作用。本项目开展的缺陷态对复合材料载流子动力学及光催化影响机理研究可为合理设计高性能TiO2基异质结光催化材料提供理论支持。