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

Arizona State University, Scottsdale AZ

Investigators

Abstract

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.