双/多核染料敏化半导体的构筑及其光催化制氢性能研究

Combustion of fossil fuels causes a series of global environmental problems, such as global warming by releasing greenhouse gas CO2, and a series of environmental pollution problems. Development of clean, environmental friendly, and sustainable energy sources has drawn much attention and becomes an important priority stratagem in many countries. Nowadays, it is generally accepted that solar energy will play an important role in the development of new energy sources since it is abundant, clean and especially renewable. Hydrogen is an ideal candidate for the replacement of the fossil fuels, because it features high combustion energy which can be stored, distributed, and used on demand and generates clean water as exhaust. Production of hydrogen (H2) by water splitting offers an obviously excellent way to capture solar energy and provide “greener” energy for the future. Although sunlight-driven water splitting is a promising strategy route to sustainable hydrogen fuel production, widespread implementation is hampered by the expense of the necessary photovoltaic and photoelectrochemical apparatus. Associated with their well-known intense absorption and diversified stability, macrocyclic derivatives have been among the excellent catalyst candidates for water splitting. The present project will be started from the preparation of a series of dual/multinuclear photosensitizers to studying the relationship between the efficiency of photocatalytic hydrogen production utilizing solar energy and the material structure which is finally towards constructing stable and efficient dye-sensitized photocatalytic hydrogen evolution systems. By means of such kind of typical green energy technologies, effective method to solve the paradox of energy desire is expected. This is believed to be of significant theoretical importance and able to lead to a great deal of economic and social benefits.

氢能具有热值高、重量轻、无污染等优点，而太阳能作为新能源的代表之一，具有极强的时效性和地域性。如何将两者优势互补，将太阳能进行转换并存储于氢能中已成为各国能源领域可持续发展的战略决策之一。本项目在借鉴国内外染料敏化太阳能电池研究成果的基础上，基于光吸收性能良好的卟啉酞菁类大环配合物，结合申请者前期在单核酞菁类大环染料中的最新进展，从3个方面开展研究（通过分子设计和结构创新，合成宽谱带响应的双/多核敏化剂；从调节能带宽度和红移匹配入手，优化半导体基底的物化性能，采用共敏化和分层敏化等方式加强负载；结合量子化学计算，探索制氢体系的内在机理），将光催化体系中的敏化剂从单核拓展到双/多核结构，加强敏化半导体的可见/近红外光响应，提高制氢体系的协同作用，从而构筑高效、稳定的宽谱带响应的双/多核染料敏化半导体光催化制氢体系，为解决能源短缺、环境污染等难题提供行之有效的途径，具有重要的理论和实用价值。

自1972年发现半导体表面可发生光解水制氢以来，利用太阳光在半导体表面光催化制氢一直被公认是一项高回报的战略性课题。将太阳能进行转换并存储于氢能中已成为各国能源领域可持续发展的战略决策之一。我国已成为世界第二大石油消费国，高效低成本制氢技术的研发更是刻不容缓。其中光催化制氢是当今新能源技术的热点课题，其作为一种廉价清洁的能源转换策略，在推动绿色低碳循环，如期实现“碳达峰、碳中和”方面显示出巨大的潜力。其制氢效率的改善可从提高体系的电子激发/注入效率和抑制电荷复合两个方面来实现。目前的研究大多集中在拓展光谱响应范围和提高电子注入效率等方面，而对如何降低电荷复合的关注较少。针对这一现状，本项目围绕光催化制氢体系关键材料的设计、合成及组装开展研究。在借鉴国内外染料敏化太阳能电池研究成果的基础上，基于光吸收性能良好的卟啉、酞菁类大环配合物，结合申请者前期在单核酞菁类大环染料中的最新进展，通过分子设计和结构创新，合成了宽谱带响应的双/多核配合物染料5-6组，光谱谱响应范围可涵盖300-1000 nm；从调节能带宽度和红移匹配入手，优化半导体基底的物化性能，采用共敏化和分层敏化等方式加强负载，合成的卟啉酞菁基共轭聚合物和窄带隙纳米晶具有更宽的光谱响应范围，其与宽带隙半导体形成的部分复合材料实现了有效的载流子分离和红光/近红外光驱动的产氢反应。此外，还构筑了Z-型机制的光催化复合体系，其能带结构和电荷转移通道更能得到有效的调控，光谱响应范围和光催化性能获得了极大的改善，其在420 nm单色光处的表观量子效率可达35%，有望实现高效的光能-化学能转换；同时，项目进一步结合量子化学计算，研究了制氢体系的内在机理，探索了构建具有宽谱带（可见/近红外光）响应、定向电荷传递和高量子效率的敏化半导体光催化制氢体系的新思路和新方法，有望为解决能源短缺、环境污染等难题提供行之有效的途径。