AVS 53rd International Symposium
    Surface Science Tuesday Sessions
       Session SS1-TuM

Paper SS1-TuM2
CO and NO Reactions over Rh Nanoparticles Supported on Ceria Thin Films@footnote 1@

Tuesday, November 14, 2006, 8:20 am, Room 2002

Session: Reactivity of Metal Clusters
Presenter: S.D. Senanayake, Oak Ridge National Laboratory
Authors: S.D. Senanayake, Oak Ridge National Laboratory
D.R. Mullins, Oak Ridge National Laboratory
Correspondent: Click to Email
The reduction of noxious automotive emissions such as CO and NO@sub X@ with the use of solid catalysts is of great importance at present due to ever tightening regulatory standards for gas emissions. Novel catalysts consisting of metal particles supported on various oxide surfaces are often employed. The oxidation reaction of CO to CO@sub 2@ and the sequential reduction of NO to N@sub 2@ are frequently found to be strongly dependent on the composition and oxidation state of the oxide support. In this work we investigated reactions over one such catalytic system, Rh/CeO@sub X@, with the use of temperature programmed desorption (TPD), soft x-ray photoelectron spectroscopy (SXPS) and near edge x-ray absorption fine structure (NEXAFS) spectroscopy. The CeO@sub 2@ and CeO@sub X@ surfaces are grown in situ by evaporation of Ce in a low-pressure O@sub 2@ ambient (1x10@super -7@ Torr) on a Ru(0001) single crystal. Rh nanoparticles are subsequently deposited onto this surface. Isotopic labeling of the substrate (Ce@super 18@O@sub X@) and reactants (@super 13@CO and @super 15@NO) were used to elucidate reaction mechanisms. Surface intermediates are identified using SXPS and NEXAFS performed at Beamline U12a at the NSLS. In addition we also present preliminary results of this same reaction under dynamic reaction conditions. The pressure gap is a very difficult obstacle to overcome in the study of real time reaction dynamics under UHV conditions. We have addressed this problem by using an effusive molecular beam of CO and NO produced by a directed-doser attached to the UHV system. We have compared the reaction on a Rh(111) single crystal surface with that on Rh nanoparticles supported on ceria. @FootnoteText@ @footnote 1@Research sponsored by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, U.S. Department of Energy, under contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC.