Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 31: Oberflächenreaktionen II

O 31.5: Vortrag

Donnerstag, 11. März 2004, 12:15–12:30, H36

Selective methanol oxidation on a Cu (110) surface — •Ling Zhou, Sebastian Guenther, and Ronald Imbihl — Institut fuer Physikalische Chemie und Elektrochemie,Universitaet Hannover

The oxidation of methanol with oxygen to formaldehyde, CO 2 , H 2 and H 2 O on a Cu (110) surface was studied under stationary reaction conditions in the 10−7 - 10−3 mbar range with rate measurements, AES, LEED and PEEM. The catalytic activity of the surface exhibits a pronounced peak at low temperature ( ≈ 480 K) and a second peak at high temperature ( ≈ 850 K). The selectivity of the stationary reaction was carefully analyzed and related the adsorbates present on the surface. A pronounced hysteresis of the reactivity during temperature ramping can be observed. It was shown that this hysteresis as well as the H 2 -formation rate is entirely determined by structural effects. All products are formed with first order kinetics with respect to oxygen partial pressure up to a certain ratio. Above this ratio with an oxygen rich gas feed, high oxygen coverage phases form inhibiting the reaction. By varying the total pressure from 10−7 mbar up to 10−3 mbar a pressure dependent temperature shift of the first reaction peak of about 20 K / decade was detected. This finding is in agreement with experiments in the range above 0.01 mbar. This result can be regarded as a first and successful step in bridging the pressure gap between UHV- and high-pressure experiments.

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