可见-近红外光响应的石墨相氮化碳/石墨烯量子点复合材料的可控制备及其光催化性能研究

Since it is of great significance to design and obtain novel efficient photocatalytic materials to alleviate the global energy crisis and environmental pollution, plentiful of studies have been focusing on acquiring the environmentally friendly and efficient photocatalysts that can take full advantage of solar energy. Recently, owing to several advantageous properties including the high stability, environmental benign and low-cost, the metal-free semiconductor of graphite phase carbon nitrite has attracted great attention in the fields of photocatalysis. However, two disadvantages involved with the inefficient utilization of solar energy and the fast recombination of photo-generated electrons and holes greatly reduce their photocatalytic activity. Based on previous studies and our early works, this project aims to develop the novel metal-free graphite phase carbon nitrite (g-C3N4) /graphene quantum dots (GQDs) photocatalytic composites that can combine the outstanding features of GQDs, such as up-converted emission, high rate of carrier mobility, good stability and broad spectral response, and the photocatalytic advantages of g-C3N4. More important, we will investigate the photocatalytic mechanism and their applications in splitting water and degrading organic pollutions with the assistance of simulated solar light. This project will not only provide new ideas for constructing the metal-free, environmentally benign and efficient photocatalysts with wide spectral response, but also offers effective technical support for their industrial applications in the future.

设计和开发高效光催化材料对缓解能源危机及环境污染具有重大意义，该领域的工作一直以获得宽光谱响应、环境友好型光催化材料作为研究焦点。不含金属的石墨相氮化碳半导体因其环境友好性在光催化领域备受青睐，但其缺点在于太阳能利用效率不高、光生电子和空穴复合速率快。根据文献调研和相关工作基础，本项目拟利用石墨烯量子点对石墨相氮化碳进行改性，从而使石墨烯量子点的上转换发光、高载流子迁移率、宽光谱响应、稳定性好等优点与g-C3N4材料的光催化优势相结合，获得不含金属、具有可见-近红外宽光谱响应、催化活性高、稳定性好的石墨相氮化碳/石墨烯量子点新型光催化材料。考察该复合材料在光解水制取氢气和降解有机污染物方面的光催化活性，通过探索反应机理，期待为开发不含金属且具有可见-近红外宽光谱响应的环境友好型高效光催化剂提供设计思路，也力争为该系列催化剂产品的实用化提供技术支持。

基于半导体的光催化剂技术由于可以将低密度的太阳能转化为高密度的化学能，例如分解水产氢和二氧化碳还原等，还可以降解水和空气中的有机污染物，是一种最为理想利用太阳能缓解能源危机和环境问题的技术。光催化材料是光催化技术的核心。然而，传统基于过渡金属的半导体存在价格昂贵、二次污染和光催化效率低等劣势。有机聚合物半导体石墨相氮化碳材料由于具有不含金属、热及化学稳定性好、可见光响应、二维层状结构等优点，在光催化领域表现出巨大的应用前景。由于传统制备方法获得的石墨相氮化碳材料存在比表面积小以及光生电子-空穴复合率高，导致其光催化效率低，限制了石墨相氮化碳在未来实际工业化应用。本项目旨在通过调控石墨相氮化碳微纳米结构、多孔结构及能带结构，从而提升其光催化性能，并深入探索石墨相氮化碳材料的制备工艺、微观结构与光催化性能的关系，并取得了一些具有代表性的成果。其中包括以廉价商用三聚氰胺纳米海绵为模板，原位热聚合尿素构筑了具有提升光催化性能的宏观三维多孔石墨相氮化碳；采用氨气气氛热刻蚀法，高效制备了具有碳缺陷和贯穿片层结构的多孔石墨相氮化碳纳米片；采用杆式超声工具，以质子化的多层氮化碳纳米片为前驱体，制备了纳米级尺寸单层石墨相氮化碳纳米片。该单层纳米片不仅具有显著增强的光催化性能，还具有优异的荧光性能；此外，本文还以三聚氰胺和卤化锂为反应原料，采用一步热聚合法制备了基于三嗪环结构单元的结晶型氮化碳片层材料，表现出比普通石墨相氮化碳更优异的可见光催化性能；在此基础上，本文提出并制备由石墨相氮化碳与结晶型氮化碳形成具有界面相异质结的复合型氮化碳，相界面异质结显著提高了光生电子-空穴分离效率，使得复合型氮化碳光催化活性明显提升。通过为期三年的针对性研究最终获得了具有宽光谱光响应的高光催化活性的光催化材料，为开发基于石墨相氮化碳材料的高效光催化剂提供新方法和新思路。