ChBE Seminar Series: Catalysis on Precious Metals in the Subnanometer Regime (Ayman M. Karim)
Speaker: Ayman M. Karim, Associate Professor, Department of Chemical Engineering, Virginia Polytechnic Institute and State University
Full title: Catalysis on Precious Metals in the Subnanometer Regime: New Properties and Reaction Pathways
Supported noble metal catalysts are extensively used in industry and their catalytic performance is strongly affected by particle size and shape. In the last decade, supported single atoms and clusters in the subnanometer size regime have attracted a lot of interest since they maximize the metal utilization and have also shown extraordinary catalytic properties for many reactions. However, to tailor the catalyst properties for specific reactions and determine possible limitations, there is a need to understand, on the atomic scale, the origin of activity and selectivity in the subnanometer regime.
In this seminar, I will present my group’s efforts in understanding the role of metal nuclearity and electronic properties in catalyzing model oxidation, hydrogenolysis and selective hydrogenation reactions. Using a suite of advanced characterization techniques (aberration-corrected electron microscopy, microcalorimetry, in-situ and in-operando DRIFTS, XPS, EXAFS and HERFD-XANES) complemented by DFT calculations and detailed kinetics measurements, the catalyst structural and electronic properties are identified and correlated with the reaction kinetics. The talk will cover how the metal nuclearity and strong interaction with the support in the subnanometer regime have a strong effect on the reaction mechanism, for CO oxidation, butane hydrogenolysis and selective hydrogenation of acetylene. The results will be discussed in relation to scaling and Brønsted-Evans-Polanyi relationships.
Dr. Karim joined the Department of Chemical Engineering at Virginia Tech as an Associate Professor in the Fall of 2014. His research is focused on the synthesis and characterization of nanomaterials, and the design of heterogeneous catalysts for energy and environmental applications. He is a co-principal investigator for the Synchrotron Catalysis Consortium (SCC) and his group uses a combination of advanced in-situ and in-operando characterization techniques (SAXS, XAFS, FTIR) to study the synthesis mechanisms of colloidal nanoparticles and catalysts and to study the reaction mechanisms on heterogeneous catalysts. He recently received the 3M Non-Tenured Faculty Award, Virginia Tech Institute for Critical Technology and Applied Science (ICTAS) Junior Faculty Award and is a member of the Young Editorial board for Journal of Energy Chemistry. He has co-authored 55 peer reviewed publications, one patent and delivered over 25 invited lectures and presentations. Prior to Virginia Tech, he worked as a senior research scientist (2008-2014) at the Pacific Northwest National Laboratory (PNNL), one among 10 U.S. Department of Energy (DOE) national laboratories managed by DOE's Office of Science. Dr. Karim earned his BSc in Biomedical Engineering from Cairo University in Egypt (2000) then moved to the U.S. and received his PhD in Chemical Engineering from the University of New Mexico working with Prof. Abhaya Datye (2001-2006) followed by a postdoctoral fellowship at the University of Delaware in the Chemical Engineering Department with Prof. Dionisios Vlachos (2007-2008).