CAS-Climate: Spectromicroscopy of Elementary Steps in Catalytic Reactions

在化学系化学测量与成像(CMI)计划的支持下，加州大学欧文分校化学系、物理系和天文学系的何伟信教授和吴如谦教授领导的研究小组正在开发一种复杂的测量方法，用于研究重要的温室气体二氧化碳的催化化学。这项研究有可能提供帮助发展碳固存化学所需的基本理解，这是一个非常重要的环境/气候科学目标。一个重要的目标是应用复杂的测量工具来探索使用单原子催化剂将二氧化碳转化为更高价值碳氢化合物的机制。通过沉积在衬底上的单个金属原子的催化作用，可以保护有价值的金属。这个项目将研究金属原子如何与反应物结合，并作为直接化学反应的催化中心，这些反应是由电子和光而不是热刺激的。该小组正在努力将原子尺度上的化学测量和成像与理论计算结合起来，以表征和可视化中间物种，这些中间物种仍然难以识别，但其观察将有助于从机理上理解，从而能够开发用于定向反应过程的催化剂。该项目寻求提供对控制二氧化碳化学至关重要的缺失知识，同时也促进研究单原子催化剂化学的精密测量和理论方法的最新水平。除了应对化学中最重要的挑战之一和减缓气候变化的全球影响外，这项工作的更广泛影响还通过强调可转移到课堂上的化学反应的基本原理而得到加强。该项目的更广泛影响将包括为附近服务不足社区的中学生举行涉及液氮和真空的示威活动。该项目的教育影响将通过与加州大学欧文分校埃德尔曼量子研究所和NSF材料研究科学与工程中心合作的教育和推广活动来增强，包括与周围大学的高中生、本科生和研究生联系的机会。原子、分子和底物之间复杂相互作用的性质多年来一直混淆了对催化反应的见解。设计有效的催化剂是能源收集和环境保护面临的最紧迫的基本和技术挑战之一。在复杂的环境和高温下，化学反应经常不分青红皂白地快速发生，通过密度泛函理论计算和大型系综统计实验很难获得反应的细节。希望能够一步一步地测量和控制化学反应和相关的中间物种。这项研究利用扫描隧道显微镜(STM)探索化学中最小的催化中心：惰性二维范德华单层或超薄绝缘膜上的单个活性原子。研究中的反应将通过不同的刺激来进行：尖端的机械运动、隧穿电子和光线照射。此外，光谱显微镜能力预计将提供对化学物种的单个化学键和骨架结构的直接真实空间可视化。要更深入地理解局部化学和反应动力学，将依赖第一性原理计算来解释数据并做出预测，以指导实验工作。该项目将侧重于将二氧化碳还原为附加值碳氢化合物作为燃料，并将研究具有不同电子、振动、自旋、结构和能量性质的中间物种。实验和理论相结合的工作旨在识别和识别这些物种，并提供关于它们属性的分子水平信息。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Measurement and Imaging (CMI) Program in the Division of Chemistry, a research team led by Professors Wilson Ho and Ruqian Wu from the Departments of Chemistry and Physics and Astronomy, respectively, at the University of California-Irvine is developing a sophisticated measurement approach for studying the catalytic chemistry of carbon dioxide, an important greenhouse gas. This research has the potential to provide fundamental understanding that is needed to help develop the chemistry of carbon sequestration a very important environmental/climate science goal. An important objective is the application of sophisticated measurement tools to probe the mechanism for conversion of carbon dioxide to higher-value hydrocarbons using single-atom catalysts. Catalysis by single metal atoms deposited on a substrate enables conservation of valuable metals. This project will examine how metal atoms bind reactants and serve as catalytic centers for directed chemical reactions that are stimulated by electrons and light, rather than by heat. The team is working to combine chemical measurement and imaging at the atomic scale with theoretical calculations in order to characterize and visualize intermediate species that remain challenging to identify but whose observation would facilitate mechanistic understanding and thereby enable the development of catalysts for targeted reaction courses. This project seeks to provide missing knowledge that is crucial for controlling the chemistry of carbon dioxide while also advancing the state-of-the-art in precision measurement and theoretical methodology for studying the chemistry of single-atom catalysts. In addition to addressing one of the most consequential challenges in chemistry and the global implications for moderating climate change, the broader impacts of the work are enhanced by the emphasis on basic principles of chemical reactions that are transferrable to the classroom. Broader impacts of the project will include demonstrations involving liquid nitrogen and vacuum for middle school students from nearby underserved communities. The educational impact of the project will be enhanced through education and outreach activities in collaboration with the University of California-Irvine Eddleman Quantum Institute and the NSF Materials Research Science and Engineering Center, including opportunities to connect with high school students and undergraduate and graduate students from surrounding universities.The nature of complex interactions between atoms, molecules, and substrates has for many years confounded insights into catalytic reactions. The design of effective catalysts is among the most urgent fundamental and technological challenges for energy harvesting and environmental protection. Chemical reactions occur rapidly and often indiscriminately in complex environment and at elevated temperature, and details of the reactions are difficult to obtain by density functional theory calculations and large ensemble statistical experiments. It is desirable to be able to measure and control chemical reactions step-by-step and associated intermediate species. This research explores with the scanning tunneling microscope (STM) the smallest catalytic centers in chemistry: a single active atom on an inert two-dimensional van der Waals monolayer or ultrathin insulating film. The reactions under study will proceed by inducing with different stimuli: mechanical motion of the tip, tunneling electrons, and light illumination. Furthermore, the spectro-microscopy capability is expected to provide direct real-space visualization of individual chemical bonds and skeletal structure of the chemical species. A deeper understanding of the local chemistry and reaction kinetics will rely on first-principles calculations to explain the data and make predictions to guide the experimental effort. This project will focus on the reduction of carbon dioxide to value-added hydrocarbons as fuels and will examine intermediate species with different electronic, vibrational, spin, structural, and energetic properties. The combined experiment-theory effort is designed to identify and identify these species and provide molecular-level information about their properties.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.