碳纤维气凝胶基异质结光催化材料的构筑及其性能研究

Utilizing photocatalysis technology to convert solar energy into chemical energy or direct degradation and mineralization of organic pollutants is a long-term solution to solve the problem of environmental pollution. Polymer semiconductor graphitic carbon nitride (g-C3N4)，possesses distinct electronic structure and chemical property，and has attracted a wide spread attention in clean energy conversation using solar power．However，the g-C3N4 photocatalyst synthesized by traditional thermal polyconsendation method has small surface area，and the photo-generated electron-hole pairs is easily to recombine，which suppressed the photocatalytic activity severely．Moreover, almost all studies reported thus far have been focused on g-C3N4 in the powder form that suffers from a complicated recovery step during the photocatalytic process, setting a hurdle for the real applications. Herein, our idea is to make full use of local resources--cotton as a fibrous template to fabricate shaped carbon fiber aerogels and simultaneously graft g-C3N4/TiO2 heterojunction photocatalyst inside the porous structure to impart functionality through the combination of in-situ hydrolysis, freeze-drying and carbonization. The macroscopic carbon fiber aerogels based photocatalyst with hierarchical porosity in the micrometer and nanometer range can promote adsorption and reaction sites during the photocatalytic process. The heterogeneous g-C3N4/TiO2 can enhance light carrier transfer and thus improve the light quantum efficiency of catalyst. Futhermore, the macroscopic 3D g-C3N4/TiO2 photocatalyst with better recovery properties for theoretical significance and practical application.

利用光催化技术将太阳能转化为化学能或降解有机污染物，是解决环境污染的有效途径。聚合物半导体石墨相氮化碳(g-C3N4)具有独特的电子结构和化学性质，然而，传统热缩聚法合成的g-C3N4粉体光催化剂比表面积小、光生电子-空穴易于复合、抑制了其光催化活性。此外，在实际水体处理中纳米粉体催化剂不仅分离困难、难以回收利用。本项目利用新疆优势资源棉花作为合成碳纤维气凝胶的前驱体，首先通过原位水解制备出多层级结构TiO2-棉花纤维复合物，将上述产物浸渍在盐酸胍溶液中，经冷冻干燥及高温碳化，拟得到具有可见光响应，易于回用的g-C3N4/TiO2-碳纤维复合气凝胶。气凝胶中丰富的微孔和中孔结构可增加吸附和反应位点，负载的g-C3N4/TiO2异质结能改善其光生载流子的分离效率。凭借气凝胶的结构特性，制备宏观块体结构的碳纤维气凝胶基复合光催化剂代替传统的纳米颗粒处理有机污染物，具有重要的理论意义和实用价值。

能源短缺和环境污染已成为制约人类社会可持续发展的重要问题，也是当前科研研究的热点。g-C3N4作为一种新型的非金属半导体光催化剂，备受关注。但光生载流子易复合，光吸收性能和反应活性位点有限等缺点限制了其光催化的效率。针对上述缺陷，本项目开展了g-C3N4基复合光催化材料制备及调控研究，研究了超分子自组装氮缺陷修饰的Ag/g-C3N4纳米纤维膜及其光催化产氢活性的研究和具有等离子共振效应的三维碳氮基异质结光催化材料的构筑及其CO2还原性能研究等工作，一方面，通过调控g-C3N4的形貌提高样品比表面积、元素掺杂拓展光响应范围和载流子迁移、利用异质结促进光生载流子分离抑制复合、引入贵金属纳米颗粒的局域表面等离子共振拓展光吸收范围等方式可以有效的提高g-C3N4的光催化活性，为高效光催化剂的设计与开发做出有益的探索。另一方面，通过发展超分子前驱体自组装的策略在g-C3N4的形貌工程和元素掺杂等方面具有良好的应用前景和应用空间。