Regensburg 2010 – scientific programme
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O: Fachverband Oberflächenphysik
O 67: Gerhard Ertl Young Investigator Award (talks of the selected canditates)
O 67.1: Talk
Thursday, March 25, 2010, 10:30–11:00, H37
Restructuring of Catalyst Surfaces under Reaction Conditions — •Feng Tao1,2, Miquel Salmeron2, and Gabor Somorjai1,2 — 1Department of Chemistry, University of California, Berkeley, California, USA, 94720 — 2Materials Science Division, Lawrence Berkeley National Lab, Berkeley, California, USA, 94720
The surface structure of catalysts and their evolution under reaction conditions is one of the crucial issues in understanding catalytic mechanisms at molecular and atomic levels. Here bimetallic nanoparticles (Rh0.5Pd0.5 and Rh0.5Pt0.5) were used as model catalysts for the in-situ study of surface structure under reaction conditions. The as-synthesized Rh0.5Pd0.5 nanoparticles are core-shell structured. However, there is no significant depth-dependence of atomic fractions of Rh and Pt in Rh0.5Pt0.5 nanoparticles. Surface structures of two Rh-based bimetallic nanoparticle catalysts during catalysis, oxidation, and reducing reactions have been systematically studied in-situ using XPS in Torr pressure ranges. The Rh0.5Pd0.5 and Rh0.5Pt0.5 nanoparticles undergo reversible changes in both atomic fractions and chemical states corresponding to the switch of reaction environments between oxidizing and catalysis (or reducing) conditions. Rh atoms in Rh0.5Pd0.5 and Rh0.5Pt0.5 segregate to surface region and are largely oxidized under oxidizing conditions, while in reducing atmospheres the Pd atoms in Rh0.5Pd0.5 and Pt atoms in Rh0.5Pt0.5 segregate to the surface regions and Rh oxides are largely reduced. The capability of restructuring nanoparticles through chemical reactions suggests a new method for the development of new catalysts.