Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 14: Poster session I (Adsorption, Epitaxy and growth, Phase transitions, Surface reactions, Organic films, Electronic structure, Methods) (sponsored by Omicron Nanotechnology GmbH)

O 14.39: Poster

Monday, March 27, 2006, 18:00–21:00, P2

Hydrogenation of 1,3-butadiene on Pd(111) and PdSn/Pd(111) surface alloys — •Breinlich Christian, Jan Haubrich, Conrad Becker, and Klaus Wandelt — University of Bonn, Institute for Physical and Theoretical Chemistry, Wegelerstr.12, 53115 Bonn

We have investigated the adsorption and hydrogenation of 1,3-butadiene on Pd(111) and PdSn/Pd(111) surface alloys under UHV conditions using TPD and HREELS. The Pd-Sn surface alloys were produced by annealing of tin layers of various thicknesses. Depending on the amount of deposited tin and the annealing temperature this procedure resulted in the formation of ordered surface alloys of (√3 × √3)R30^∘ or p(2 × 2) superstructure, which were characterized by LEED, AES and UPS. The adsorption and reaction of 1,3-butadiene was investigated by TPD. After 1,3-butadiene adsorption at 55 K the desorption of the multilayer was found near 120 K on all surfaces. Further heating lead to desorption of part of the monolayer around 180 K and to partial hydrogenation to butene at 200 - 230 K. At higher temperatures the remaining species decompose into hydrogen and surface carbon. The partial hydrogenation is highly selective since no desorption of butane has been found. The branching ratio of desorption vs. hydrogenation vs. decomposition on the bare surface and the surface alloys is clearly a function of the surface stoichiometry. HREELS investigations reveal the adsorption modes of 1,3-butadiene on these surfaces.