Song Boao, Yang Timothy T, Yuan Yifei, Sharifi-Asl Soroosh, Cheng Meng, Saidi Wissam A, Liu Yuzi, Shahbazian-Yassar Reza
Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, United States.
Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States.
ACS Nano. 2020 Apr 28;14(4):4074-4086. doi: 10.1021/acsnano.9b08757. Epub 2020 Apr 20.
The decoration of two-dimensional (2D) substrates with nanoparticles (NPs) serve as heterostructures for various catalysis applications. Deep understanding of catalyst degradation mechanisms during service conditions is crucial to improve the catalyst durability. Herein, we studied the sintering behavior of Pt and bimetallic Au-core Pt-shell (Au@Pt core-shell) NPs on MoS supports at high temperatures under vacuum, nitrogen (N), hydrogen (H), and air environments by gas-cell transmission electron microscopy (TEM). The key observations are summarized as while particle migration and coalescence (PMC) was the main mechanism that led to Pt and Au@Pt NPs degradation under vacuum, N, and H environments, the degradation of MoS substrate was prominent under exposure to air at high temperatures. Pt NPs were less stable in H environment when compared with the Pt NPs under vacuum or N, due to Pt-H interactions that weakened the adhesion of Pt on MoS. under H, the stability of Au@Pt NPs was higher in comparison to Pt NPs. This is because H promotes the alloying of Pt-Au, thus reducing the number of Pt at the surface (reducing H interactions) and increasing Pt atoms in contact with MoS. The alloying effect promoted by H was more pronounced in small size Au@Pt NPs resulting in their higher sintering resistance in comparison to large size Au@Pt NPs and similar size Pt NPs. The present work provides key insights into the parameters affecting the catalyst degradation mechanisms on 2D supports.
用纳米颗粒（NPs）修饰二维（2D）基底可作为用于各种催化应用的异质结构。深入了解催化剂在使用条件下的降解机制对于提高催化剂的耐久性至关重要。在此，我们通过气室透射电子显微镜（TEM）研究了在真空、氮气（N）、氢气（H）和空气环境中，高温下Pt和双金属金核铂壳（Au@Pt核壳）NPs在MoS载体上的烧结行为。主要观察结果总结如下：虽然颗粒迁移和聚并（PMC）是导致真空、N和H环境下Pt和Au@Pt NPs降解的主要机制，但在高温下暴露于空气时，MoS基底的降解较为突出。与真空或N环境下的Pt NPs相比，Pt NPs在H环境中稳定性较差，这是由于Pt-H相互作用削弱了Pt在MoS上的附着力。在H环境下，Au@Pt NPs的稳定性高于Pt NPs。这是因为H促进了Pt-Au合金化，从而减少了表面Pt的数量（减少了H相互作用）并增加了与MoS接触的Pt原子。H促进的合金化效应在小尺寸Au@Pt NPs中更为明显，导致其与大尺寸Au@Pt NPs和类似尺寸Pt NPs相比具有更高的抗烧结性。本工作为影响二维载体上催化剂降解机制的参数提供了关键见解。
