Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 20: Oberflächenreaktionen I

O 20.6: Vortrag

Dienstag, 9. März 2004, 12:30–12:45, H45

Dehydrogenation of Methanol on Rhodium/Vanadium Surface Alloys and the influence of preadsorbed oxygen — •Georg Krenn, Klaus D. Rendulic, and Robert Schennach — Institute of Solid State Physics, Graz University of Technology, Austria

The dehydrogenation of methanol on metal surfaces has regained interest recently due to the development of methanol powered fuel cells. Dehydrogenation of methanol on Rh(111) leads to the formation of carbon monoxide and hydrogen only. The reaction products are the same on the Rh(111)/V alloy surfaces, but the reaction kinetics differ significantly. On a Rh(111)/V subsurface alloy and on a Rh(111)/V islands surface the reaction probabilities stay high up to about 400 K and 550 K, respectively, in contrast to about 200 K on Rh(111). On the Rh(111) surface with V islands a decrease in the reaction probability occurs due to buildup of carbon layers on the V islands. Preadsorption of oxygen on the three surfaces reverses the trend from the oxygen free surfaces, so that the Rh(111) surface shows the highest activity. With preadsorbed oxygen water and carbon dioxide are found as additional reaction products. The difference between the oxygen covered surfaces and the oxygen free surfaces is discussed in terms of two different initial reaction steps on the surface. With preadsorbed oxygen a proton transfer reaction from the OH group of methanol to adsorbed oxygen seems to be the first reaction step, while on the oxygen free surface conventional dehydrogenation takes place.