Regensburg 2002 – scientific programme

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O: Oberflächenphysik

O 24: Oberfl
ächenreaktionen (II)

O 24.10: Talk

Tuesday, March 12, 2002, 18:30–18:45, H44

Methanol Adsorption and Reaction on Pd (111) and on a Pd/V Surface Alloy — •Robert Schennach and Klaus D. Rendulic — Institute of Solid State Physics, Graz University of Technology, Austria

The adsorption and subsequent dissociation reaction of methanol on Pd (111) has been the focus of several studies due to the importance of this reaction as a model for the production of methanol from hydrogen and carbon monoxide. While the question in the literature, whether or not the C-O bond of adsorbed methanol on Pd (111) can be opened, has been settled recently, there is no experimental proof for the mechanistic explanation of this reaction pathway. Using a supersonic molecular beam apparatus, we present an indirect experimental proof, that a hydrogen bond between two neighboring methanol molecules on the Pd (111) surface is necessary, in order to break the C-O bond. The formation of this hydrogen bond can be inhibited by changing the electronic state of the surface due to the formation of a Pd/V surface alloy. This leads to a complete suppression of the C-O bond activation in methanol. On the other hand, the same result can be achieved by using a molecular beam of methanol with a high translational energy. This effect is explained in terms of a steric effect and/or dissociative adsorption instead of molecular methanol adsorption at high methanol energies.