卟啉/多酸可控共组装及其可见光催化产氢研究

High performance photosensitizer has been revealed critical for the efficient conversion of solar energy to hydrogen energy via visible light catalytic water splitting. This program focuses on the molecular level co-assembly of porphyrin and polyoxometalate cluster with controlled morphology and inner structure by mimicking the photosynthesis system of plant. The purpose is to solve the problems of short excited state electron-hole lifetime and low visible light utilization via synergistic effect of the strong visible light absorption, as well as the excellent electron conduction property of polyoxometalate. The molecular structures of porphyrin and polyoxometalate were modified to adjust the energy level of the two molecules as well as the inner structure of co-assembly, with the aim of enhancing the excited state electron transfer efficiency and solving the problem of short electron-hole lifetime. Also, the ultrathin nanostructure was fabricated via micelle confined template method, to shorten the distance to active site and enhance the photocatalytic hydrogen evolution efficiency. Finally, the relationship between the material composition and morphology and hydrogen evolution efficiency of co-assembly will be thoroughly investigated in order to get a series of photosensitizer with high performance, towards establishing a solid theoretical basis for developing new type hydrogen evolution photosensitizer with high performance.

高性能光敏剂是将低密度的太阳能高效、稳定的转化为可存储氢能的关键。针对当前所使用的光解水制氢光敏剂可见光利用率低、激发态电子-空穴对寿命短的问题，本项目拟通过模拟植物光合作用系统光敏剂的内部结构，将卟啉与多酸分子簇进行分子级可控共组装，利用卟啉分子较大的可见光吸收截面，结合多酸分子优异的电子传导性能，制备结构有序、形貌可控的复合光敏剂用于可见光催化水分解制氢。一方面，通过对卟啉和多酸分子簇的分子修饰，使二者的能级更好的匹配，提高卟啉的激发态电子到多酸的转移效率；另一方面，通过胶束限域模板法构筑超细、超薄的微纳复合结构，进一步缩短光生电子迁移到产氢活性位点的距离，两方面协同作用抑制载流子的复合，解决激发态电子-空穴对寿命短和产氢效率低的难题。深入研究共组装体的组成、结构、形貌与光解水制氢性能之间的构效关系，为新型高性能光敏剂的研发提供理论指导和技术支撑。

通过光解水制氢将低密度的太阳能转化为可存储的氢能对解决当前能源和环境问题具有重要的意义。本项目通过模拟植物光合作用系统光敏剂的内部结构，将卟啉与多酸分子簇进行可控共组装，实现了高效的可见光的利用及高效的太阳能到氢能的转化。在项目实施过程中，为了解决疏水性卟啉与具有较大极性的多酸的界面相容性问题，促进组装体的形成及两者之间高效的电子转移，我们首先引入辅助配体g-C3N4作为前驱体，通过高温水热的过程使其氢键发生解离从而形成含丰富胺基官能团的g-C3N4的寡聚体片段，进一步与卟啉进行共组装，形成了带丰富活性官能团的亲水性卟啉组装体ZnTPP/g-C3N4，实现了疏水性卟啉的表面修饰，为下一步引入多酸分子提供条件，系统研究了其形貌、组成、结构和复合机理，发现经过表面修饰的卟啉不但具有亲水性，还有利于卟啉的有序组装，显著增强卟啉组装体的光催化产氢活性。在此基础上，引入多酸，用一步溶剂热法和分步包裹法合成了共组装结构（ZnTPP/g-C3N4/POMs）和核壳结构（ZnTPP/g-C3N4@POMs）两种不同的光催化剂，实现了卟啉和多酸的有效复合，构筑了新型的非贵金属光催化水分解制氢系统，研究了光催化效率与催化剂的组成和结构的构效关系，并进一步揭示了多酸催化的光催化产氢的机理，为后续新型的光催化产氢催化剂的研究提供了理论依据和技术支撑。