title: Stability and Temperature-Induced Agglomeration of Rh Nanoparticles Supported by CeO2.
abstract: The effects of reduction by H2 and by heat treatment in vacuum and in O2 flow on Rh particle size changes of Rh/CeO2 samples were studied by X-ray photoelectron spectroscopy (XPS), high-resolution electron microscopy (HRTEM), and CO adsorption followed by diffuse reflectance infrared spectroscopy (DRIFTS). Low-temperature (373-423 K) reduction of Rh without agglomeration is demonstrated. An average particle size of 2.3 ± 1.1 nm was measured by HRTEM regardless of the metal loading (1-5%). On Rh/CeO2, a significant particle size increase of the Rh particles was detected on heating (773 K). In this work, we suggest that the temperature-induced surface decrease resulting from the sintering of Rh is favored only for well-dispersed particles. XP spectra revealed that the mobile oxygens of CeO2 fundamentally determine the oxidation state of the supported metals. At elevated temperature, the oxidation of the reduced support surface as well as the metal component takes place because of the segregation of ceria oxygens. When the aggregated particles were reoxidized, the redispersion of Rh was observed probably because of the formation of Rh-O-Ce bonds.
authors.affiliation: Department of Physical Chemistry and Materials Science, ‡Department of Applied and Environmental Chemistry, and §MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged , H-6720 Szeged, Hungary.
authors.forename: Erika
authors.initials: E
authors.lastname: Varga
authors.affiliation: Department of Physical Chemistry and Materials Science, ‡Department of Applied and Environmental Chemistry, and §MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged , H-6720 Szeged, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Pusztai
authors.affiliation: Department of Physical Chemistry and Materials Science, ‡Department of Applied and Environmental Chemistry, and §MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged , H-6720 Szeged, Hungary.
authors.forename: Albert
authors.initials: A
authors.lastname: Oszkó
authors.affiliation: Department of Physical Chemistry and Materials Science, ‡Department of Applied and Environmental Chemistry, and §MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged , H-6720 Szeged, Hungary.
authors.forename: Kornélia
authors.initials: K
authors.lastname: Baán
authors.affiliation: Department of Physical Chemistry and Materials Science, ‡Department of Applied and Environmental Chemistry, and §MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged , H-6720 Szeged, Hungary.
authors.forename: András
authors.initials: A
authors.lastname: Erdőhelyi
authors.affiliation: Department of Physical Chemistry and Materials Science, ‡Department of Applied and Environmental Chemistry, and §MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged , H-6720 Szeged, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Kónya
authors.affiliation: Department of Physical Chemistry and Materials Science, ‡Department of Applied and Environmental Chemistry, and §MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged , H-6720 Szeged, Hungary.
authors.forename: János
authors.initials: J
authors.lastname: Kiss