Direct Atomic-Scale Investigation of the Coarsening Mechanisms of Exsolved Catalytic Nanoparticles

15 July 2024, Version 2

Abstract

Exsolution-active catalysts allow for the formation of highly active metallic nanoparticles, yet their long-term thermal stability remains a challenge. In this work, the dynamics of exsolved Ni nanoparticles are probed in situ with atomically resolved secondary electron imaging in an environmental STEM. STEM pre-characterization shows embedded NiOx nanostructures within the parent oxide. Subsequent in situ exsolution demonstrates that two populations of exsolved particles form with distinct metal-support interactions and coarsening behaviors. Nanoparticle migration which fits random-walk kinetics is observed, and particle behavior is shown to be analogous to a classical wetting model. Additionally, DFT calculations indicate that particle motion is facilitated by the support oxide. Ostwald ripening processes are visualized simultaneously to migration, including particle redissolution and particle ripening.

Keywords

Exsolution
Secondary Electron Imaging
Environmental Scanning Transmission Electron Microscopy
Nanoparticles

Supplementary materials

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Supplemental Information
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Supplemental material. Includes detailed experimental and simulation methods, additional in-situ and ex-situ characterization to support the conclusions of the main paper, and supplemental DFT calculations.
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Supplemental videos
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In-situ videos, detailed description of each video is included in supplementary information file.
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