晶态庚嗪基氮化碳的合成及其光催化性能研究

Graphitic Carbon nitride (g-C3N4) has been widely used to settle intractable energy and environmental issues because of its visible light active, cheap, abundant, simple in structure and can be fabrications in large scale. However, the g-C3N4 exhibits unsatisfactory in photocatalytic properties. A possible reason for the poor photcatalytic activities is the inefficiency in separating and transporting of photo-generated electrons and holes due to the unavoidable disordered structure or defects in the noncrystalline carbon nitride. In privous investigate, we found that the shortcomings may mainly origin from the coexist of triazine and heptazine structure. In this proposed project, crystalline heptazine-based carbon nitride, which may inhibit the recombine of photogenerated electron-hole, will be synthesized by using the form of supramolecular aggregates before polycondensation and incorporating ions into melem when it is polymerized. The influence of melem’s purity, condensation time and temperature, and doping ions on the microstructure of crystalline heptazine-based carbon nitride will be analyzed. The mechanism of the excitation, separation, and transmission of photogenerated electron-hole pairs with the microstructure will be clarified. The results of this project are expected to provide experimental foundation and theoretical supports for developing the carbon nitride photocatalyst which has high efficient and stabilizing photocatalytic properties.

氮化碳光催化材料具有可见光响应、成本低廉、结构简单、容易规模化制备等特点，在能源与环境领域极具应用前景。然而，目前报道的氮化碳大都是存在结构缺陷的非晶态材料，其较低的光生电子-空穴分离效率和载流子输运能力，致使其光催化性能不高。在前期工作中我们发现三嗪单元的不规则排列可能是其难以结晶及结构缺陷较多的主要原因。本项目针对氮化碳材料上述缺点，采用多步处理方式，通过熔盐热处理及溶剂热合成工艺制备晶态七嗪基氮化碳，实现光生电子-空穴的有效分离和输运。研究合成条件、前驱物及介质离子对氮化碳微结构的影响规律，分析并阐明材料微结构影响光生电子-空穴的激发、分离、传输的作用机制，获得具有良好光催化性能的晶态七嗪基氮化碳材料，为开发高效、稳定的氮化碳光催化材料提供实验基础和理论依据。

实现太阳能光催化分解水制氢技术的规模化应用是推动氢能源经济的最有竞争力和发展潜力的途径之一。要实现这个目标，制备出高效廉价环保的光催化剂是首要基础。本项目以合成晶态氮化碳为目标，通过设计合成及修饰策略实现氮化碳庚嗪单元的有序组合，进而促进光生载流子的传输实现光生电子-空穴分离效率。首先，我们通过构建的全庚嗪基超分子合成晶态氮化碳，合成的材料光解水制氢效率较PCN提升了58倍。其次，通过多种途径研究了影响碱金属配位晶态氮化碳的因素，发现了不同因素之间影响氮化碳光催化性能的协同作用。此外，我们对氮化碳微结构包括分子结构、材料表面特性也进行了研究，它们从不同的 方向提高材料光催化性能，这些调控策略与氮化碳晶体结构协同作用将是进一步提高其光催化性能的有效途径。本项目为提升氮碳基光催化剂的光催化性能提供了研究基础，拓展了研究思路。