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Evolution of Metastable Structures in Bimetallic Catalysts from Microscopy and Machine-Learning Molecular Dynamics

preprint
revised on 13.02.2020 and posted on 14.02.2020 by Jin Soo Lim, Jonathan Vandermause, Matthijs A. van Spronsen, Albert Musaelian, Christopher R. O’Connor, Tobias Egle, Yu Xie, Lixin Sun, Nicola Molinari, Jacob Florian, Kaining Duanmu, Robert J. Madix, Philippe Sautet, Cynthia M. Friend, Boris Kozinsky
Restructuring of interface plays a crucial role in materials science and heterogeneous catalysis. Bimetallic systems, in particular, often adopt very different composition and morphology at surfaces compared to the bulk. For the first time, we reveal a detailed atomistic picture of the long-timescale restructuring of Pd deposited on Ag, using microscopy, spectroscopy, and novel simulation methods. Encapsulation of Pd by Ag always precedes layer-by-layer dissolution of Pd, resulting in significant Ag migration out of the surface and extensive vacancy pits. These metastable structures are of vital catalytic importance, as Ag-encapsulated Pd remains much more accessible to reactants than bulk-dissolved Pd. The underlying mechanisms are uncovered by performing fast and large-scale machine-learning molecular dynamics, followed by our newly developed method for complete characterization of atomic surface restructuring events. Our approach is broadly applicable to other multimetallic systems of interest and enables the previously impractical mechanistic investigation of restructuring dynamics.

Funding

EFRC - Integrated Mesoscale Architectures for Sustainable Catalysis (IMASC, DE-SC0012573)

Robert Bosch LLC

History

Email Address of Submitting Author

nmolinari@seas.harvard.edu

Institution

Harvard University

Country

United States of America

ORCID For Submitting Author

0000-0002-2913-7030

Declaration of Conflict of Interest

We declare no conflict of interest.

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