Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 24: Postersitzung (Epitaxie und Wachstum, Oxide und Isolatoren, Elektronische Struktur, Oberfl
ächenreaktionen, Adsorption an Oberfl
ächen, Organische Dünnschichten)

O 24.37: Poster

Mittwoch, 26. März 2003, 14:30–17:30, P1

Reactivity of clean and oxygen-covered copper surfaces — •Sung Sakong and Axel Groß — Physik-Department T30, Technische Universität München, 85747 Garching, Germany

Copper surfaces play an important role in the methanol steam reforming process. In order to contribute to a microscopic understanding of this technologically very relevant reaction we have studied the reactivity of clean and oxygen-precovered copper surfaces by means of density functional theory (DFT) calculations within the generalized gradient approximation. Using hydrogen adsorption as a microscopic probe, we have particularly focused on strain effects in the reactivity. In contrast to other surfaces, we do not find any unique trend in the dissociation barrier heights and adsorption energies as a function of the lattice strain. The reasons for this behavior in terms of the underlying electronic structure have been carefully analysed.

Furthermore, we have addressed the methanol oxidation over copper by studying the initial reaction step, the dehydrogenation of methanol. Interestingly enough, while the coadsorption of oxygen significantly hinders the hydrogen dissociation on copper, the abstraction of the hydroxyl hydrogen from adsorbed methanol is greatly facilitated by the presence of coadsorbed oxygen atoms which is in good agreement with experiments. It turns out that the direct oxygen-hydrogen interaction is crucial for an understanding of this promotion effect.