Abstract: I will show that dynamic catalytic interfaces exhibit great structural fluxionality in conditions of catalysis, and populate many distinct structural and stoichiometric states, which form a statistical ensemble. Multitude of metastable states in this ensemble dictate the catalytic activity, selectivity, and durability, as well as size-specific behaviours. Every intermediate of the catalyzed reaction is bound to a different ensemble-state of the catalyst. For every reaction step, the most active catalyst state is not the most stable. Thus, catalyst dynamics is an essential part of the catalytic process. Many rules of catalysis need a revision within this new paradigm. Scaling relations routinely break down. Phase diagrams contain many structures per phase. Operando spectroscopy interpretation needs to be done differently, and it may miss the true active sites because it reports on the majority sites that may not be most catalytic. The theory of sintering and the idea of magic numbers need a revision. Etc. Several catalytic systems will be shown to illustrate these points: semiconductor-supported Pt clusters and cluster alloys used for hydrocarbon dehydrogenation for endothermic cooling, Cu oxide clusters used for oxidative dehydrogenation, and clusters on graphite used for ORR. Most of this work is done in close collaboration with experiments that we either explain, or that tests our predictions. Some of our results will hopefully prompt experimental developments. For example, detecting dynamic minority species of the catalytic interface remains a challenge.
Bio-sketch: Anastassia Alexandrova is a Professor in the Department of Chemistry and Biochemistry, UCLA. She obtained a B.S./M.S. Diploma with highest honors, from Saratov University, Russia, her Ph.D. in theoretical physical chemistry from Utah State University, and was then a Postdoctoral Associate and an American Cancer Society Postdoctoral Fellow at Yale University. Anastassia joined the faculty of UCLA and CNSI in 2010. The focus of her laboratory is theory and computation for design and multi-scale modeling of functional materials: dynamic catalytic interfaces, artificial metalloenzymes, molecular qubits and their assemblies, and quantum materials. She is a recipient of numerous awards, such as NSF CAREER Award, Sloan Fellowship 2013, DARPA Young Faculty Award 2011, Fulbright Fellowship 2016, and ACS WCC Rising Star Award 2016, 2020 ACS Phys Early Career Award in Theoretical Chemistry, 2021 Max Planck-Humboldt medal, as well as UCLA’s Hanson-Dow award for excellence in teaching 2016, Herbert Newby McCoy award for excellence in faculty research 2016, undergraduate research mentorship award 2018, and 2019 distinguished teaching award (the highest honor for teaching given in UCLA).
Koffler - Room 218
Anastassia Alexandrova Faculty Professor, Department of Chemistry and Biochemistry, UCLA
Hosted by Dr. Steven Schwartz