Direct observation of chemical dynamics in Pt catalyst during CO oxidation by operando electron microscopy
Dr. Milivoj Plodinec
Department of Inorganic Chemistry, Fritz Haber Institute of the Max Planck Society, Berlin, Germany
Date: Wednesday, December 16, 2020
Time: 9 AM Central European Summer Time (CEST) | 3 PM China Standard Time (CST)
Date: Wednesday, December 16, 2020
Time: 8 PM Central European Summer Time (CEST) | 11 AM Pacific Daylight Time (PDT)
This webinar will be given 2 times. Choose the time slot that best suits you.
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Catalysts have been studied for over a century, however many questions remain unanswered about the fundamental factors influencing the activity, selectivity as well as the deactivation of catalysts at work. Therefore, it is crucial to gain this knowledge to develop better, more efficient catalysts for industrially relevant reactions. The key point still missing is the knowledge of the structure-activity properties of the working catalyst. In spite of the long-term study, and regardless of our advances in synthesis and characterization methods, the empirical approach towards discovery of new catalysts still prevails. This is a very inefficient and time-consuming endeavour and a consequence of the complexity of the catalytic process. Indeed, some fundamental questions regarding the structure-activity correlation of active catalysts can only be addressed based on direct observation. To date, most electron microscopy (EM) studies of catalysts have been performed under ex-situ conditions, i.e., before and after catalytic testing. Observation of samples in vacuum and at room-temperature can, by principle, not reveal the working state of a catalyst, and has, in the past, rather contributed to a misleading picture of static catalysts.[1,2] Therefore, operando electron microscopy is a powerful tool which provides direct insights into time-resolved structural and morphological transformations of the material during operating condition on the atomic scale, providing the correlation between catalyst structure and activity.
In first part of the talk, I will show that the application of complementary operando EM techniques (in-situ TEM and SEM) allow us to directly visualize reaction induced structural and morphological changes of a Pt catalyst in CO oxidation reaction [3,4] across length scales. Our multi-scale approach combining in-situ TEM and SEM allows us to study collective dynamics at the µm scale in the SEM, and to relate them to atomic processes that are observed by operando TEM. Simultaneously, we are capable of bridging the pressure gap between surface-science model studies and real-world industrially relevant conditions.
In the second part of the talk the focus will lie on the possible influence of the electron beam on catalyst dynamics during in-situ observations. I will show the possible significant impact of the electron beam on the Pt NPs coarsening and the dependence of the applied gaseous environment, the temperature and electron beam dose.
 Su, D.S., B. Zhang, and R. Schlögl, Electron microscopy of solid catalysts–transforming from a challenge to a toolbox. Chem. Rev. 2015. 115(8), p. 2818-82.
 Schlögl, R., Heterogenous catalysis. Angew. Chem. Int. 2015. 54(11), p. 3465-3520.
 Plodinec, M., et al., Chemical dynamics and their impact on the reactivity of Pt nanoparticles during CO oxidation by Operando TEM. ACS Catal. 2020. 10(5), p.3183-3193.
 Plodinec, M., et al., Versatile homebuilt gas feed and analysis system for operando TEM of catalysts at work, Microsc. Microanal. 2020. 26(2), p. 220-228.