多酸基量子点敏化可见光催化分解水制氢体系的构筑及性能研究

The construction of a clean, low-carbon, safe and efficient modern energy system is the key task of the “13th Five-Year” energy development plan. One of the important ways of obtaining hydrogen energy is the photocatalytic water splitting utilizing solar energy. Most of the catalysts in molecular photocatalytic water-reducing systems still suffer from the relatively high cost, the deactivation due to the ligand dissociation, decomposition or hydrogenation, which restrict the improvement of the hydrogen production. Polyoxometalates (POMs) have already proved to be the excellent molecular catalyst candidates of hydrogen production due to their low cost for preparations, high stability and rich redox activity, however, this system is still focused on the noble-metal photosensitizers, which undergo the expensive price and the instability with long time illuminations. Therefore, we will introduce the noble metal-free photosensitizers water-soluble semiconductor quantum dots into the POMs-based hydrogen evolution system in this project, the suitable POMs molecular catalysts are designed and synthesized to match with the light-harvesting materials based on their advantages including the superior photostability, tunable redox potentials, wide visible spectrum absorptions, and the propensity for photoinduced electron transfer, etc.. The noble metal-free efficient photocatalytic hydrogen evolution system could be constructed through optimizing POMs structures and the combination of the photophysical experiments and density functional theories for investigating the synergetic catalysis mechanism and structure-property relationship between POMs and photosensitizers. We hope to establish the new, efficient and stable photocatalytic water splitting hydrogen evolution systems with the co-promotion of POMs and quantum dots through the implementation of this project, which will also provide new ideas and ways for the development of fully water splitting systems.

构建清洁低碳、安全高效的现代能源体系是“十三五”能源发展规划的重点任务。太阳光催化分解水是获得氢能源的重要途径之一。光催化水还原体系的多数分子催化剂成本较高，由于配体解离、分解或氢化而极易失活，限制产氢性能提升。多酸制备成本较低，兼具高稳定性与氧化还原活性，已成为优秀产氢分子催化剂。然而，目前该体系仍以价格昂贵、长时间光照不稳定的贵金属光敏剂为主。因此，本项目拟将非贵金属水溶性半导体量子点光敏剂引入多酸产氢体系，利用该类捕光材料光稳定性优异、氧化还原电势可调、宽光谱吸收和有利于光诱导电子传递等优势，设计合成与之匹配的多酸分子催化剂。通过优化多酸结构，采用光物理实验与密度泛函理论相结合探究多酸与光敏剂之间的协同催化机制和构效关系，构筑高效非贵金属可见光催化制氢体系。通过本项目的实施，以期建立新型、高效、稳定的多酸与量子点共同促进的光催化分解水制氢体系，为发展全分解水体系提供新思路和新途径。

构建清洁低碳、安全高效的现代能源体系是“十三五”能源发展规划的重点任务。太阳能是地球上最丰富且可再生的清洁能源，如何高效利用太阳能对于解决当今世界严重的环境污染问题和资源枯竭问题具有重要意义。多酸制备成本较低，兼具可调的结构与组成，优异的氧化还原活性，在能源转换过程中扮演着重要角色。本项目主要的研究目标在于设计合成结构稳定的新型多酸化合物，筛选出适合的多酸团簇与捕光材料或者二维材料结合，探究其在光催化水分解产氢等能源转换领域的应用。在项目执行期内，以多酸合成为重要研究基础，通过优化多酸结构提高性能，我们构建了一系列太阳光驱动的多酸基能源转换体系，主要实现了（1）可见光驱动铜碲核取代型多酸光催化分解水制氢。铜多酸作为分子催化剂，系统探究了其在分子捕光材料驱动下光催化分解水制氢活性及相关的氧化还原猝灭机制，采用多种分析测试手段阐明了均相催化体系中多酸催化剂稳定性的科学问题；（2）PW11Co多酸与类石墨烯Co0.85Se复合对电极材料。该项工作率先将多酸扩展到双面照射染料敏化太阳能电池的研究中，通过不同过渡金属取代型多酸的结构优化有效实现了电池器件性能提升。多酸作为电子聚集体可以提高硒化物对I-/I3-氧化还原电对的电荷转移能力，并加速I3-的还原；（3）r-GO@多酸复合催化剂光化学合成氨。利用多酸掺杂可有效降低r-GO聚集程度，从而暴露出更多活性位点，提高氮气吸附量。在温和条件下，上述材料展示出高效光化学合成氨活性。机理研究表明该纳米催化剂表现出宽吸收光谱与强还原性，易于吸收光能并激发光生电子活化氮气分子。总体来说，本项目多酸基光化学体系的构建可为清洁能源的实用化提供新思路和新途径。