CAS: Functional Nanoglues for Robust and Efficient Single-Atom Catalysis

新的催化转化过程可能会对全球能源安全产生重大影响，并导致更清洁的环境。许多化学生产和排放控制过程使用贵金属作为催化剂来加速化学反应。贵金属在工业催化剂中的使用是不可持续的，因为这些金属的丰度低且成本高。使用负载的单金属原子进行催化转化可以解决这些问题。单原子催化剂广泛应用的关键挑战是其在使用过程中的稳定性。在这个项目中，亚利桑那州立大学的Jingyue (Jimmy) Liu博士正在开发“纳米胶”来稳定所支持的单金属原子并提高它们的催化性能。该项目旨在解决对支撑金属原子催化的基本理解，并为开发对环境和经济具有重要实际应用的单原子催化剂提供设计工具。刘教授通过高分辨率电子显微镜冬季学校影响教育，主要由研究生参加。此外，科学与工程体验（SCENE）项目为10-12年级的高中生提供尖端的科学研究体验。在化学系化学催化项目的资助下，亚利桑那州立大学的Jingyue (Jimmy) Liu博士正在研究如何通过将单个金属原子（如Pt， Pd, Rh, Ru， Ir或Au）限制在分离的，超小型功能氧化物纳米团簇（如CeOx， TiOx和CoOx）中来定位并同时增强其催化性能。这些纳米胶被均匀地接枝到高表面积的坚固支架上（例如，二氧化硅或氧化铝）。有了这样的催化剂设计，预计在催化剂活化过程中（例如，在250℃- 500℃的H2下）和/或在还原环境下的高温催化反应中，单个金属原子或小金属团簇不会烧结。使用支撑的、孤立的金属原子作为催化活性中心，不仅可以最大限度地提高金属的使用效率，而且可以使活性位点均匀分布。这些因素对于调整目标催化反应的选择性是重要的。催化剂的设计允许金属原子在其相应的隔离纳米胶岛内移动，但不能穿过纳米胶形成更大的颗粒。纳米胶不仅充当“双面胶带”，牢固地固定金属原子和高表面积载体，而且还为目标催化活性和/或选择性提供所需的功能。纳米胶岛的尺寸范围为0.5-2.0纳米，以适应高水平的金属负载。对纳米胶基单原子催化剂进行了CO氧化、CO优先氧化、水气转换、重整和加氢/脱氢反应的测试。更广泛的影响包括将研究成果纳入年度高分辨率电子显微镜冬季研讨会（主要由来自美国各地的研究生参加），培训研究生和本科生研究学生，并通过科学与工程经验（SCENE）计划指导高中生，该计划致力于为10-12年级的高中生提供尖端的科学研究经验。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

New catalytic conversion processes may significantly impact global energy security and lead to a cleaner environment. Many chemical manufacturing and emission control processes use precious metals as catalysts to speed up the chemical reactions. The use of precious metals in industrial catalysts is not sustainable because of the low abundance and high cost of these metals. The use of supported single metal atoms for catalytic transformation may address these problems. The critical challenge for broad applications of single-atom catalysts is their stability during use. In this project, Dr. Jingyue (Jimmy) Liu of Arizona State University is developing "nanoglues" to both stabilize the supported single metal atoms and enhance their catalytic performance. This project is addressing fundamental understanding of catalysis by supported metal atoms and is providing design tools for developing single atom catalysts with practical applications important to the environment and the economy. Professor Liu impacts education through the ASU Winter School on High Resolution Electron Microscopy, attended primarily by graduate students. In addition, the SCience and ENgineering Experience (SCENE) program is providing cutting-edge science research experiences to high school students in grades 10-12. With funding from the Chemical Catalysis Program of the Division of Chemistry, Dr. Jingyue (Jimmy) Liu of Arizona State University is developing a fundamental understanding of how to localize, and simultaneously enhance the catalytic properties of, single metal atoms (e.g., Pt, Pd, Rh, Ru, Ir or Au) by confining them to isolated, ultra-small functional oxide nanoclusters (e.g., CeOx, TiOx, and CoOx). These nanoglues are uniformly grafted onto a high-surface-area robust support (e.g., silica or alumina). With such a catalyst design, it is expected that single metal atoms or small metal clusters do not sinter during the catalyst activation process (e.g., by H2 at 250 C - 500 C) and/or during catalytic reactions at elevated temperatures under reducing environment. The use of supported, isolated metal atoms as catalytically-active centers not only maximizes the metal usage efficiency but also makes it possible to have uniform distribution of active sites. These factors are important for tuning the selectivity of a targeted catalytic reaction. The catalyst design allows metal atoms to move within their corresponding isolated nanoglue islands but not across the nanoglues to form larger particles. The nanoglue not only acts as a “double-sided tape” to strongly hold both the metal atoms and the high-surface-area support but also provides the desired function for the targeted catalytic activity and/or selectivity. The sizes of the nanoglue islands range 0.5-2.0 nm to accommodate high levels of metal loading. The nanoglue-based single-atom catalysts are being tested for CO oxidation, preferential oxidation of CO, water-gas shift, reforming, and hydrogenation/dehydrogenation reactions. Broader impacts include incorporating research results in an annual Winter Workshop of High Resolution Electron Microscopy (attended primarily by graduate students from across the US), training of graduate and undergraduate research students, and mentoring of high school students through the SCience and ENgineering Experience (SCENE) program dedicated to providing cutting-edge science research experiences to high school students in grades 10-12.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.