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    Catalysis at Multiple Length Scales: Crotonaldehyde Hydrogenation at Nanoscale and Mesoscale Interfaces in Platinum-Cerium Oxide Catalysts

    Year: 2017

    Journal: J. Phys. Chem. C, Volume 121, JUN 29, page 13765–13776

    Authors: Mueanngern, Yutichai; Yang, Xin; Tang, Yu; Tao, Franklin Feng; Baker, L. Robert

    Organizations: Air Force Office of Scientific Research under AFOSR [FA9550-15-1-0204]; Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy [DE-SC0014561]; NSF Career Award [NSF-CHE-146212]

    Crotonaldehyde hydrogenation is carried out on a series of Pt-CeO2 catalysts to investigate the mechanism of enhanced C=O bond hydrogenation by an active oxide-metal interface. We show that deposition of CeO2 nanoparticles onto a Pt surface leads to two types of Pt-CeO2 interfaces: (1) the nanoscale interface defined by the contact of individual CeO2 nanoparticles with the Pt surface and (2) a larger, mesoscale interface defined by the boundary between domains of self-assembled nanoparticles and the surrounding clean Pt substrate. Surprisingly, although the nanoscale interface accounts for greater than 90% of the total number of 3-phase boundary sites in the catalysts tested as shown by TEM analysis, C=O bond hydrogenation kinetics scale exclusively with the larger, mesoscale interface. Using in situ ambient pressure XPS, we show that these kinetics are not the result of variations in the CeO2 oxidation state due to H spillover or the result of Pt decoration by the migration of reduced Ce atoms during reaction. Instead, we hypothesize that reaction is rate-limited by the surface migration of crotyl-oxy intermediates as they form oil CeO2 nanoparticles and subsequently diffuse and react on surrounding Pt.
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