双分子结型水分解光催化剂的设计合成及其作用机制研究

Improving the quantum efficiency of photocatalytic water splitting for hydrogen production is the core mission of scientific research on the energy photocatalysis. On the basis of previous research accumulation and preliminary experimental exploration, overall considering from both thermodynamic and kinetic aspects of the reaction, the project proposes a new idea for designing photocatalytic composite materials by constructing dual molecular junctions, which promote electron and hole transfer, respectively, on the photoreductive and photooxidative active crystal facets of semiconductor materials using the principle and method of surface organometallic chemistry. The synergistic mechanism of action of dual interfacial heterojunctions of multiplex nanocomposite photocatalysts for the splitting of water to hydrogen and oxygen will be investigated. The composition, structure, and physical mechanism of migration and transfer pathways of photogenerated electrons and holes through the interface formed in nanocomposite photocatalysts for water splitting will be studied. The relationship between the structure and property of composite photocatalysts will be clarified through the systematic characterization of structure and composition as well as the performance evaluation. The physical mechanisms of the coupling between charge spatial separation of crystal facets and inner electric field in junctions will be clarified. The key factors to influence the efficiency of water splitting on photocatalyst surface will be revealed. The key factors to determine the reaction system of photocatalytic water splitting for hydrogen and oxygen production will be clarified. Combined with theoretical calculation, the photocatalytic molecular model will be proposed. This project is of great theoretical and extraordinary practical significances in guiding the design and preparation of efficient composite photocatalysts for water splitting, and enriching photocatalytic basic theory.

提高光催化分解水产氢反应过程的光量子效率是能源光催化科学研究的核心任务。本项目基于以往研究积累和前期探索，从反应的热力学和动力学两个方面综合考虑提出借用表面金属有机化学的原理和方法在半导体材料光还原和光氧化活性晶面上分别构筑促进电子和空穴迁移的双分子结的复合光催化材料设计新思路。探究多元复合纳米光催化剂双界面异质结协同分解水产氢产氧的作用机制；研究光催化分解水产氢产氧复合光催化剂界面光生电子和光生空穴迁移和传输通道的组成、结构和物理作用机制。通过系统的结构、组成表征和性能评价，阐明复合光催化剂的构效关系，弄清晶面电荷空间分离和结内生电场耦合的物理机制，揭示影响催化剂表面分解水效率的关键因素，搞清决定光催化水分解产氢产氧反应体系的关键因素，结合理论计算，建立分子作用模型。该研究在指导高效分解水复合光催化剂的设计制备和丰富光催化基础理论上都具有重要的理论价值和实际意义。

提高光催化分解水产氢反应过程的光量子效率是能源光催化科学研究的核心任务。项目设计制备了系列异质结型光催化剂，深入研究了光催化剂的构效关系、作用机理等基本科学问题。项目取得如下主要研究进展：（1）在暴露（101）晶面的TiO2上构建RuO2/TiO2异质结和Ru/TiO2肖特基结，制备了Ru/TiO2/RuO2双结型光催化剂；揭示了RuO2/TiO2和 Ru/TiO2双结提高TiO2光催化分解水性能的协同效应。（2）利用基质Cp2MoCl2与基底TiO2表面活性羟基的化学反应，在TiO2（001）晶面上构建“Ti-O-Mo”分子结，揭示其在界面电荷传输和产氢过程中的作用；在此基础上，继续接枝产氧助催化剂，构建促进光生空穴迁移的分子结，制备可实现纯水分解的双分子结光催化剂，此部分还在继续研究中。（3）研究了g-C3N4表面Ni助催化剂的晶体结构和微观结构对g-C3N4光催化产氢活性的影响，发现无定形NiO的负载拓宽了g-C3N4可见光吸收，提供了更多的产氢活性位点，使NiO/g-C3N4界面之间形成了“C-O-Ni”分子结，促进了光生电子的迁移，从而更加有效地提高了光催化产氢活性。（4）研究了溶剂热条件下氮化碳的生长过程，制备了三嗪基低聚物@氮化碳分子结型光催化剂，首次提出了“自敏化”氮化碳结构，发现“自敏化”增强了氮化碳的光吸收、促进了电荷分离和迁移，从而提高了光催化产氢活性；制备了B均匀掺杂的三嗪基低聚物@氮化碳分子结型光催化剂，发现B掺杂和三嗪低聚物染料的协同作用进一步提高了氮化碳的光催化产氢活性；在三嗪基低聚物@氮化碳上包覆了MoS2，制备了MoS2@三嗪基低聚物@氮化碳双结型产氢催化剂，提出了三嗪基低聚物→氮化碳→MoS2的矢量电子迁移模型。（5）在FTO、TiO2等基底上生长了高质量的氮化碳基共聚物膜实现光电分解水，发现氮化碳薄膜与基底之间的共价键连接保证了紧密的接触和界面电荷的高效传输，三嗪和三聚三嗪组成的聚合网络结构更有利于光吸收及光生电荷的生成与传输；此外，发现“三嗪-庚嗪”基氮化碳聚合物薄膜电极具有较好的电催化分解水性能。这些研究结果为设计高效分解水材料提供了一些新视野。