externe Veranstaltungen
25. Juni 2024, 16:00 bis 17:00
Friedrich Esch, Technical University of Munich, TUM School of Natural Sciences, Department of Chemistry, Garching/Germany
Seminar
Catalysts on reducible oxide supports often change their activity significantly at elevated temperatures due to the strong metal-support interaction (SMSI), which induces the formation of an encapsulation layer around the noble metal particles. While the encapsulation is well established for nanoparticles, it remains to be explored for small, sub-nm clusters – how does the encapsulation layer form, and what is its impact on cluster stabilization and catalytic activity?
In the present work, we employ scanning tunneling microscopy (STM, upgraded by sophisticated fast tools for movie acquisition and cluster tracking [1]), pulsed valve molecular beam “sniffer” measurements in combination with X-ray photoelectron spectroscopy to study atomically precise Ptn clusters (5≤n≤20) deposited on Fe3O4(001) and to compare the results to other reducible oxide supports, TiO2(110) and CeO2(111). On magnetite, upon stepwise annealing, we observe the succession of lattice oxygen reverse spillover, encapsulation, cluster coalescence, and Ostwald ripening, with respective sintering onset temperatures that scale with size and thus cluster footprint [2,3]. Small clusters of up to 10 atoms still diffuse at the verge of encapsulation, and we can track this diffusion in real-time. On titania, we show that the support reduction is critical for the encapsulation of nanoparticles but much less for clusters.
Veranstaltung Details
- Veranstaltungsort
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SEM.R. DB gelb 05 B
1040 Wien
Wiedner Hauptstraße 8-10/E134 - Veranstalter
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IAP
Manuela Marik
marik@iap.tuwien.ac.at - Öffentlich
- Ja
- Kostenpflichtig
- Nein
- Anmeldung erforderlich
- Nein