Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 3: Oberfl
ächenreaktionen I

O 3.2: Vortrag

Montag, 24. März 2003, 11:30–11:45, HSZ/02

Oxidation of methanol on an oxygen precovered Cu(111) surface — •Silke Pöllmann, Andreas Bayer, Christian Ammon, and Hans-Peter Steinrück — Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen

On a pure Cu(111) surface methanol adsorbs and desorbs molecularly. The oxidation of methanol to formaldehyde with methoxy as an intermediate only takes place on an oxygen precovered Cu(111) surface. This reaction was studied by means of high resolution X-ray photoelectron spectroscopy (XPS) with monochromized Al K α radiation, ultraviolet photoelectron spectroscopy (UPS), and temperature programmed desorption (TPD). In the temperature range between 100 and 160 K, part of the adsorbed methanol is dehydrogenated to methoxy. This can clearly be seen by a shift of the O 1s and C 1s peaks in the XP spectra to lower binding energies. In the UP spectra the peaks of molecular methanol disappear and the peaks of methoxy develop. The efficiency of this reaction depends on the quantity of the precovered oxygen; the maximum amount of methoxy is formed at a coverage of 0.25 ML oxygen. The TPD measurements show that methoxy desorbs dissociativly as formaldehyde and hydrogen at a substrate temperature of 430 K. As conclusion, a reaction scheme is proposed.