二维材料限域单原子催化剂的设计及其CO2还原机制的同步辐射原位XAFS研究

The efficient conversion of CO2 is an important way to solve the energy crisis and global warming issue. The key is to develop catalysts with high activity, high selectivity and high stability. However, the lack of research on the structural characteristics and mechanism of the catalytic sites under working conditions has always been the bottleneck restricting catalyst design. Using the exclusive, well-defined single-atom catalyst confined in two-dimensional material as a model, this project intends to monitor the dynamic change of the local structure on active centers under the CO2 reduction conditions, by means of operando X-ray absorption fine structure (XAFS) at the Beijing Synchrotron Radiation Facility. Combined with the reaction intermediates captured by in-situ infrared spectroscopy, we will establish the correlation between local structure changes of active centers and dynamic processes such as CO2 adsorption, activation and transformation, and eventually a clear physiochemical image of CO2 reduction process on the single-atom site will be described. On this basis, the local atomic structure and electronic structure of single-atom sites will be regulated to optimize the catalytic performance. Through theoretical analysis and experiments, we will clarify the regulation principle of the local structure under static conditions. This project will provide experimental and theoretical basis for the design of highly active and highly selective catalysts for CO2 reduction.

CO2的高效转化是解决能源危机和全球变暖问题的重要途径，其核心是发展高活性、高选择性和高稳定性的催化剂，但对工作条件下催化位点的结构特征及作用机制的研究缺乏一直是制约催化剂设计的瓶颈。本项目拟以局域结构单一、明确的二维材料限域单原子催化剂为模型，依托北京同步辐射装置，借助原位X射线吸收精细结构（XAFS）谱学技术监测CO2还原条件下活性中心局域结构的动态变化。结合原位红外光谱捕获反应中间产物，建立活性中心局域结构变化与CO2吸附活化、转化等动态过程的关联，描绘出单原子位点上CO2还原过程的清晰物理化学图像。在此基础上，调控单原子位点的局域原子结构和电子结构，优化CO2催化性能；通过实验表征结合理论分析，阐明静态条件下单原子位点局域结构变化对催化性能的调控机制。本项目的开展将为高活性、高选择性CO2还原催化剂的设计提供实验和理论基础。

在国家自然科学基金委大科学装置联合基金项目（批准号：U1832168）的资助下，负责人着眼于CO2高效、定向转化中的关键科学问题，围绕模型催化体系的可控制备、原位表征、催化作用本质和增强机制开展研究，取得如下进展：（1）利用MOFs孔道的可裁剪性和限域效应，提出了一种构筑结构单一、明确的单原子催化剂的通用策略；（2）开展催化剂活性基元的分子尺度设计与调控，实现了CO2高效、选择性转化制CO、甲酸盐；（3）开发出用于原位XAFS测试的CO2还原反应池，借助XAFS等原位技术揭示了工况下催化剂活性基元的原子/电子结构特征和作用机制；（4）提出了固-液相变策略来诱导金属合金几何结构和电子态突变，实现了对催化反应路径和反应产物的调控。项目的开展为分子水平上理解CO2还原活性基元的本质提供了实验和理论支持。