In-situ and Ex-situ Microscopy and Spectroscopy Study of Catalytic Materials

in situ microscopy;catalysts;structure transformation;Materials Science and Engineering;Engineering;Materials Science and Engineering

Zhang, ShuyiGraham, George W ;

University of Michigan

关键词: in situ microscopy;    catalysts;    structure transformation;    Materials Science and Engineering;    Engineering;    Materials Science and Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/136930/shuyiz_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Heterogeneous catalysts play a crucial role in chemical reactions through changing the reaction rate or selectivity. Most catalysts work under gaseous or liquid environments at elevated pressure and temperature, and their structure and composition are likely to change under reactive environments. Such changes have profound influence on the catalyst’s performance and stability. Thus, understanding the structures of catalysts under realistic conditions with atomic precision is crucial to the design of better materials for challenging chemical transformations. In the past decade, the majority of in-situ electron microscopy studies involving gas reaction were conducted in an Environmental Transmission Electron Microscope (ETEM), where the pressure is typically 1/100 of the pressure used in a realistic environment. To overcome this obstacle, we used a MEMS-based closed cell technique to study a variety of gas solid reactions, including (1) atomic-scale reconstructions that characterize classical and adsorbate mediated Strong Metal Support Interaction (SMSI), (2) dynamic structural evolution of a Pd@CeO2 core shell catalyst for methane combustion, and (3) sintering mechanisms of Pt particles supported on high surface area alumina. Besides these in-situ studies, a novel ex-situ microscopy technique which can dramatically enhance the resolution and contrast of embedded nanoclusters will also be discussed.