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SUMMARY:About interfaces and supports in catalysis
DTSTART;VALUE=DATE:20180608
DTSTAMP:20260407T041959Z
UID:567bee7a0794f70a077e21fd29ae67652e90d9fa53d78ec693a96aaa
CATEGORIES:Conferences - Seminars
DESCRIPTION:Jeroen A. van Bokhoven  ETH Zurich and Paul Scherrer Institu
 te\nCatalysts are the workhorses of the chemical industry\, and play an e
 ssential role in energy-conversion processes and pollution abatement. Nov
 el catalysts and processes must be developed to make our society sustain
 able. Such development is greatly helped by the understanding of how the 
 catalyst functions. The achievement of such relationship is the main aim 
 of our research.\nCatalysts often consist of nano-sized catalyst particle
 s on a support. It has been recognized since long that the role of the su
 pport is not only to stabilize the catalytically active particles of part
 icular size\, shape and composition\, but that they may actively participa
 te in the catalytic reaction. Specific reaction steps may occur completel
 y on the support or at the metal-support interface. In other cases\, the
  support may be responsible for the communication between different catal
 ytic entities by stabilizing and facilitating transport of species over i
 ts surface\, a process called spillover. \nIn my talk\, I will describe
  some of our contributions in this field. Ceria is an often-used catalyst
  support and catalytic material because of its ability to reversibly stor
 e oxygen. Thus\, in oxidation reactions\, oxygen activation may occur on
  ceria and the reaction at the interface of metal and support. The role o
 f Ce3+ is often invoked to explain catalytic activity\, however\, a quan
 titative understanding of its role is lacking. Using transient X-ray emi
 ssion and absorption spectroscopy\, we were able to distinguish between C
 e3+ that participates in a catalytic cycle\, oxidation of carbon monoxi
 de over Pt/CeO2\, and Ce3+ that does not contribute to catalytic convers
 ion and is thus a spectator.The reaction takes place at the metal-suppor
 t interface and the rate of reaction correlates to the rate of ceria redu
 ction\, not the oxygen storage capacity.\nSpillover of hydrogen over reduc
 ible and non-reducible supports is often suggested to be responsible for 
 a catalytic action at a distance. To quantify the phenomenon of hydrogen 
 spillover\, we designed a supported metal catalyst\, which contains plati
 num and iron oxide particles with a distance that is controlled to a nano
 meter. The further development of single-particle spectroscopy enabled v
 isualization of the phenomenon of hydrogen spillover. As expected\, hydr
 ogen atoms can freely move over a titania surface as electron-proton pair
 . On alumina\, the situation is more complex and a gradient of hydrogen 
 coverage away from the platinum particle is observed. The strong competiti
 on of water with the same adsorption sites\, make the occurrence of hydro
 gen spillover over an alumina surface much less likely.\n\nReferences:\n
 Catalytically Active and Spectator Ce3+ in Ceria-Supported Metal Catalyst
 s\,  Kopelent R.\, van Bokhoven\, J. A.\, Szlachetko J.\, Edebeli J.\, 
 Paun C.\, Nachtegaal M.\, Safonova O. V. Angew. Chem. Int. Ed. 54\, 872
 8 (2015)\n\nCatalyst support effects on hydrogen spillover\,  Karim\, W.
 \, Spreafico\, C.\, Kleibert\, A.\, Gobrecht\, J.\, VandeVondele\, J.\, E
 kinci\, Y.\, van Bokhoven\, J.A. Nature 541\, 68 (2017)\n\n \n\nLink to
  the webpage of the speaker
LOCATION:CE 1 5 https://plan.epfl.ch/?room==CE%201%205
STATUS:CONFIRMED
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