同步辐射光电子能谱在高效固氮光催化剂设计中的应用

Photocatalytic nitrogen fixation, a process through which atmospheric nitrogen could be converted into ammonia with the presence of photocatalyst and light, is of chemical and biological significance for achieving artificial fixation of nitrogen under ambient condition. The absorption and activation of nitrogen on the catalyst surface as well as the band structure of catalysts are the key factors that affecting the efficiency of nitrogen fixation. This project aims at designing advanced photocatalysts for nitrogen fixation based on two-dimensional bismuth-based semiconductors, and exploring the controllable synthetic methods for ultrathin bismuth-based materials. Based on first-principles theoretical calculations and modern physical characterization methods such as positron annihilation spectroscopy and electron spin resonance spectroscopy, we investigate structure-function relationships in nitrogen fixation process, interrogating the influences of defect structure and crystal facet orientation on the photocatalytic activity. Synchrotron radiation photoelectron spectroscopy is employed to study the evolution of chemical bonding at surface active sites and the reactive nitrogen intermediates during catalytic process, thus revealing the dynamic process during nitrogen activation. The results of this project will give a deep understanding on the catalytic mechanism of nitrogen photofixation, providing theoretical and experimental guidance for the design of efficient nitrogen fixation catalysts and achieving significant improvement in the yields of nitrogen photofixation.

光催化固氮是指在光照条件下，通过催化剂将游离的氮气转化为氨氮化合物的过程，该反应实现了温和条件下的人工固氮，具有重要的生物和化学意义。催化剂合适的能带结构和对氮气的吸附活化过程是影响光催化固氮效率的关键因素。本项目拟以基于二维铋基半导体高效固氮催化剂的设计为目标牵引，探索二维铋基半导体可控制备的方法；利用正电子湮没谱、电子自旋共振谱等现代物理表征手段和基于第一性原理的理论计算，研究二维超薄固体的缺陷结构、晶面取向等因素与其催化固氮性能的构效关系；基于同步辐射光电子能谱技术开展固氮过程中催化剂表面活性原子的键合变化规律以及氮活化中间产物的研究，揭示催化剂表面的氮活化动力学过程。预期成果将加深对固氮反应催化机制的认识，为设计高效固氮催化剂提供理论和方法指导，实现光催化固氮效率的显著提升。

本项目以铋基半导体为主要研究对象，负责人聚焦其在光催化小分子(N2, O2, CO2等)活化领域的应用，通过(原位)同步辐射表征研究催化过程中的关键科学问题，探究材料结构与性能之间的构效关系。发展了系列低维固体材料制备方法，实现了铋基半导体的可控宏量制备，提出了系列电子结构调控手段，如空位、掺杂、晶面工程、表面功能化等方法，并拓展上述方法至别的低维半导体体系，取得了系列研究成果。基于同步辐射技术研究了材料的电子结构特征，使用原位同步辐射红外技术、XPS技术等研究了系列半导体材料在光催化活化氮气、二氧化碳、氧气等能源小分子中的催化机制，为实现催化性能的优化提供了理论和实验基础。基于以上研究，负责人在J. Am. Chem. Soc. (5篇)，Nature Commun.，Adv. Mater.等化学、材料重要期刊发表论文20篇，应邀撰写综述及进展论文3篇。