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Article Abstract
Platinum exhibits desirable catalytic properties, but it is scarce and expensive. Optimizing its use in key applications such as emission control catalysis is important to reduce our reliance on such a rare element. Supported Pt nanoparticles (NPs) used in emission control systems deactivate over time because of particle growth in sintering processes. In this work, we shed light on the stability against sintering of Pt NPs supported on and encapsulated in AlO using a combination of nanocrystal catalysts and atomic layer deposition (ALD) techniques. We find that small amounts of alumina overlayers created by ALD on preformed Pt NPs can stabilize supported Pt catalysts, significantly reducing deactivation caused by sintering, as previously observed by others. Combining theoretical and experimental insights, we correlate this behavior to the decreased propensity of oxidized Pt species to undergo Ostwald ripening phenomena because of the physical barrier imposed by the alumina overlayers. Furthermore, we find that highly stable catalysts can present an abundance of under-coordinated Pt sites after restructuring of both Pt particles and alumina overlayers at a high temperature (800 °C) in CH oxidation conditions. The enhanced stability significantly improves the Pt utilization efficiency after accelerated aging treatments, with encapsulated Pt catalysts reaching reaction rates more than two times greater than those of a control supported Pt catalyst.
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Article Synopsis
- Strong metal-support interactions (SMSIs) can cause platinum (Pt) to be encapsulated by oxide supports, typically observed in reducible oxides like TiO and NbO.
- This study demonstrates that amorphous native surface oxide of aluminum nanocrystals (AlNCs) can also exhibit SMSI-induced Pt encapsulation when subjected to hydrogen reduction at 300 °C, leading to isolated Pt single-atom sites being exposed for catalysis.
- The findings suggest that the native oxide on AlNCs allows for a well-defined environment for Pt atoms and promote further research into SMSIs with various materials, potentially leading to enhanced photocatalytic applications due to their unique plasmonic properties.