Following the Dynamics of Nanoparticle Surfaces in Search of New Catalytic Pathways

Key challenges that motivate our ongoing work are: 1) heterogeneity of active species and sites, 2) their coexistence with spectator species and 3) dynamicity that can be directly responsible for their mechanisms.

Our work on the last topic ranges from studies of collective dynamics of supported metal nanoparticles in reaction conditions to site – specific dynamics primarily responsible for their reactivity. I will show how we leveraged that knowledge to propose a new catalyst for CO oxidation and reverse water gas shift reactions that maximized the use of those dynamic sites.

In the second part of the talk the focus will be on exploiting the dynamic restructuring of a bimetallic catalyst in reaction conditions for resolving the minority, reaction-active species in the presence of spectators. We applied a modulation excitation (ME) - XAS approach to the studies of the Pd-Au bimetallic nanocatalysts via the gas (H₂, O₂ or He) concentration modulation.

Our work solved three pieces of the puzzle: 1) Isolating the spectra of minority (3-7 at.%) active species from those corresponding to the inert spectators, 2) deciphering the actual atomistic structure of the reaction-relevant surface species (Pd oxides, hydrides and atomically dispersed Pd, depending on Pd concentration) and 3) obtained new information on the mechanism of formation and decomposition of Pd species formed on the surface. The extension of this method to other functional materials will be discussed.

Anatoly Frenkel is a Professor in the Department of Materials Science and Chemical Engineering at Stony Brook University and a Senior Chemist (Joint Appointment) at the Division of Chemistry, Brookhaven National Laboratory.

He received M.Sc. degree from St. Petersburg University and PhD degree from Tel Aviv University, all in physics, followed by a postdoctoral appointment at the University of Washington. His research interests focus on development and applications of in situ and operando synchrotron methods to solve a wide range of materials problems, with most recent emphases on catalysis, ranging from nanoparticles to “single-atom” catalysts, electromechanical and filtration materials, quantum dots, as well as machine learning methods for structural analysis and design of nanomaterials. He is a founding Principal Investigator and the Spokesperson for the Synchrotron Catalysis Consortium at Brookhaven National Laboratory. He is a Fellow of the American Physical Society.