Liccardo Gennaro, Cendejas Melissa C, Mandal Shyama C, Stone Michael L, Porter Stephen, Nhan Bang T, Kumar Abinash, Smith Jacob, Plessow Philipp N, Cegelski Lynette, Osio-Norgaard Jorge, Abild-Pedersen Frank, Chi Miaofang, Datye Abhaya K, Bent Stacey F, Cargnello Matteo
Department of Chemical Engineering and SUNCAT Center for Interface Science and Catalysis, Stanford University, Stanford, California 94305, United States.
SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
J Am Chem Soc. 2024 Aug 28;146(34):23909-23922. doi: 10.1021/jacs.4c06423. Epub 2024 Aug 13.
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.
铂具有理想的催化性能，但它稀缺且昂贵。优化其在排放控制催化等关键应用中的使用对于减少我们对这种稀有元素的依赖至关重要。用于排放控制系统的负载型铂纳米颗粒（NPs）会随着时间的推移而失活，这是由于烧结过程中的颗粒生长所致。在这项工作中，我们结合纳米晶体催化剂和原子层沉积（ALD）技术，揭示了负载在AlO上并被其包裹的铂纳米颗粒对烧结的稳定性。我们发现，通过ALD在预先形成的铂纳米颗粒上形成的少量氧化铝覆盖层可以稳定负载型铂催化剂，显著减少烧结引起的失活，正如其他人之前所观察到的那样。结合理论和实验见解，我们将这种行为与氧化铂物种由于氧化铝覆盖层施加的物理屏障而发生奥斯特瓦尔德熟化现象的倾向降低联系起来。此外，我们发现，在CH氧化条件下于高温（800°C）对铂颗粒和氧化铝覆盖层进行重构后，高度稳定的催化剂会出现大量配位不足的铂位点。这种增强的稳定性在加速老化处理后显著提高了铂的利用效率，包裹型铂催化剂的反应速率比对照负载型铂催化剂高出两倍以上。
