CAS-Climate: Spectromicroscopy of Elementary Steps in Catalytic Reactions

加州大学欧文分校化学系化学测量与成像项目（CMI Program）的支持下，由化学系、物理系和天文系的Wilson Ho教授和Ruqian Wu教授领导的研究小组正在开发一种先进的测量方法，用于研究二氧化碳（一种重要的温室气体）的催化化学。这项研究有可能提供必要的基本理解，以帮助发展碳封存化学，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先进的测量工具来探测使用单原子催化剂将二氧化碳转化为更高价值的碳氢化合物的机理。通过沉积在基底上的单个金属原子的催化作用能够保护有价值的金属。该项目将研究金属原子如何结合反应物，并作为由电子和光而不是热刺激的定向化学反应的催化中心。该团队正在努力将原子尺度的联合收割机化学测量和成像与理论计算相结合，以表征和可视化中间物种，这些中间物种仍然难以识别，但其观察将促进机理理解，从而能够开发用于目标反应过程的催化剂。该项目旨在提供对控制二氧化碳化学至关重要的缺失知识，同时推进精密测量和理论方法的最新技术，以研究单原子催化剂的化学。除了解决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的化学反应的基本原则而得到加强。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演示液氮和真空。该项目的教育影响力将通过与加州大学欧文-埃德曼量子研究所和NSF材料研究科学与工程中心合作的教育和外展活动得到增强，包括有机会与周边大学的高中生和本科生及研究生进行交流，了解原子、分子之间复杂相互作用的本质和底物多年来混淆了对催化反应的理解。有效催化剂的设计是能源收集和环境保护方面最紧迫的基础和技术挑战之一。化学反应在复杂的环境和高温下快速且经常不加选择地发生，并且反应的细节难以通过密度泛函理论计算和大型系综统计实验获得。希望能够逐步测量和控制化学反应和相关的中间物质。本研究利用扫描隧道显微镜（STM）探索了化学中最小的催化中心：惰性二维货车德瓦尔斯单层或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进行诱导：尖端的机械运动，隧穿电子和光照。此外，光谱显微镜的能力，预计将提供直接的真实空间可视化的个别化学键和骨架结构的化学物种。对局部化学和反应动力学的更深入理解将依赖于第一原理计算来解释数据并做出预测来指导实验工作。该项目将侧重于将二氧化碳还原为作为燃料的增值碳氢化合物，并将研究具有不同电子，振动，自旋，结构和能量特性的中间物种。实验与理论相结合的努力旨在识别和鉴定这些物种，并提供有关其特性的分子水平信息。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

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.