Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 90: Metals and semiconductors: Epitaxy and growth

O 90.3: Vortrag

Freitag, 30. März 2012, 11:00–11:15, A 060

Characterization of Pt_xCu_1-x alloys on Pt(111) surfaces as model catalysts for core shell nanoparticles. — •Stephan Beckord, Albert K. Engstfeld, and R. Jürgen Behm — Ulm University, Institute of Surface Chemistry and Catalysis, D-89069 Ulm, Germany

Core-shell nanoparticles consisting of a bi- or multialloy core enclosed by a layer of a pure metal often show interesting catalytic properties. One example are PtxCu1-x alloy core Pt shell particles, which show an increased catalytic reactivity towards the oxygen reduction reaction [1] or the water gas shift reaction [2] compared to the respective monometallic particles.

To study the effect of the Pt_xCu_1-x core on the Pt shell, we prepared nanostructured bimetallic planar model surfaces under ultra high vacuum (UHV) conditions, by evaporation of Cu on a Pt(111) surface followed by annealing for (surface) alloy formation. Subsequent deposition of a Pt monolayer film results in a model system closely resembling the structure of a bimetallic core-shell nanoparticle. The resulting surfaces were characterized by scanning tunneling microscopy (STM) and auger electron spectroscopy (AES) to elucidate the composition, morphology and the distribution of the different species in the surface. From these data we will determine the dominant factors for surface alloy formation. [1] *R. Strivastava, P. Mani, N. Hahn, and P. Strasser, Angewandte Chemie, 46, 8988 (2007). [2]*J. Knudsen, A. U. Nilekar, R. T. Vang, J. Schnadt, and F. Besenbacher, J. Am. Chem. Soc. 120, 6485 (2007).