金属纳米颗粒修饰光催化剂表/界面的作用机理及反应动力学研究

Photocatalysis have been extensively investigated world-widely in the past decades for sustainable energy production, organic synthesis, and environmental applications. However the quantum efficiencies of photocatalytic reactions under visible light radiation conditions still need to be geared up to meet the demand of industrial operations. Surface modification of photocatalysts by metal nanoparticles (NPs) as co-catalyst has been considered to be one the most successful approaches to improve photocatalytic performances via spatial separation of photo-excited charges. Various synthesis methods have been applied for the deposition of metal NPs on photocatalysts for H2 production, CO2 reduction, and water purification applications, and it has been recognised that the physical properties of metal NPs (i.e., metal identity, particle size, and microstructure) influence the performance drastically. Fundamental researches in surface science revealed that the properties of metal NPs and the interaction between semiconductor and metal NPs governed the electronic properties of metal-semiconductor systems, thus are essential in enhancing photocatalytic performances. However, due to the complexity of photocatalytic reactions, very few researches have been attempted to address the question of how and why the metal NPs influence the performance in photocatalytic reaction conditions, thus limiting rational design and synthesis of highly active photocatalysts. This project is aiming to gain better fundamental understanding of the semiconductor-metal NPs interaction in real photocatalytic reaction conditions. The kinetics of photoexcited e- that are trapped on metal NPs, the identity and possibility of re-excitation of e- at different energy levels and environments, and the impact of photo-induced radical species on selective photocatalytic reactions will be investigated. To realise this, well-defined photocatalyst-metal NPs systems with tuneable physical parameters synthesised by controllable techniques will be investigated using self-developed in-situ molecular probing techniques and electron paramagnetic resonance coupled with theoretical calculations.

由于人类对可持续能源，化工产品，及环境治理的需求不断增加，光催化技术在过去几十年里成为全世界的研究热点之一。但绝大部分光催化剂在可见光辐照下量子效率极低，限制了光催化技术的工业应用。金属纳米粒子助催化剂修饰光催化剂表面可以分离空穴-电子对并延长其寿命，提高光催化产氢，二氧化碳还原，及污水处理等过程的量子效率。表面科学研究表明金属纳米颗粒的物性及金属-半导体间的相互作用会影响光催化剂系统的电子结构，进而影响催化活性。但是，光催化反应条件下金属纳米颗粒的作用机制尚不明确，限制了高性能光催化剂的设计。 本项目拟在真实反应条件下，通过原位分子探针技术及电子顺磁共振技术研究物性参数可控的金属纳米颗粒-光催化剂系统中（1）金属纳米颗粒表面储存的自由电子的动力学过程；（2）光催化剂不同能级激发态电子二次激发及界面电荷转移现象；（3）金属纳米粒子对反应自由基及光催化选择性的影响。

由于人类对可持续能源，化工产品，及环境治理的需求不断增加，光催化技术在过去几十年里成为全世界的研究热点之一。但绝大部分光催化剂在可见光辐照下量子效率极低，限制了光催化技术的工业应用。此外，利用光催化手段实现高效，高选择性合成高附加值化学品还非常具有挑战。金属纳米粒子助催化剂修饰光催化剂表面可以分离空穴-电子对并延长其寿命，提高光催化产氢及污水处理等过程的量子效率。表面科学研究表明金属纳米颗粒的物性及金属-半导体间的相互作用会影响光催化剂系统的电子结构，进而影响催化活性及选择性。但是，光催化反应条件下金属纳米颗粒的作用机制尚不明确，限制了高性能光催化剂的设计。.本项目在真实反应条件下，通过原位分子探针技术，电子顺磁共振技术及原位红外-质谱联用技术系统的研究了物性参数可控的金属纳米颗粒-光催化剂系统中（1）金属纳米颗粒表面储存的自由电子的动力学过程；（2）金属纳米粒子对反应机理，中间产物，自由基及光催化选择性的影响。本项目还通过优化催化剂表面氢吸附能的设计思想制备出高性能可见光催化剂，用于实现太阳光照条件下氢转移反应，选择性合成高附加值产物。..本项目通过结合原位谱学技术及成像技术，首次提出了光催化多元醇转化机理及反应速控步，并揭示了不同金属催化助剂的作用机制，对催化剂的设计具有重要的指导意义。本项目还系统性的研究了Pd催化助剂与TiO2载体相互作用的机制，并发现光催化剂表面的自由基寿命及种类可以通过调控TiO2载体的尺寸及结晶度实现。此外，本项目首次提出了光控选择性有机合成的方案，并初步实现了该过程工业级放大，对光催化合成高附加值有机物具有重要的示范及理论指导意义。本项目还提出了耦合碱催化加速光催化氢转移反应的方案，对光催化合成高附加值有机物具有重要的示范及理论指导意义。本项目共发表SCI期刊收录文章8篇，其中包括第一作者，通讯作者及共同通讯作者发表6篇（Nat. Commun.; JACS; ACS Catal.; J. Catal.）。学术专著2部。