Hydrogenation of carbon monoxide on Ni(111) investigated with surface X-ray diffraction at atmospheric pressure

Using a specially designed UHV chamber that can be pressurized to several atmospheres, we investigated the production of methane from a mixture of CO and H-2 close to atmospheric pressure using a Ni(1 1 1) surface as model catalyst. The reaction products were monitored with a gas analyzer and the surface structure with the surface X-ray diffraction technique. At temperature between 100 and 200 degreesC approximately, a Ni3C epitaxial film develops on the surface and no methane production occurs. At temperatures above 400 degreesC, clear methane production was detected while no ordered carbide film was present on the surface. During the reaction, the Ni crystal truncation rods are almost identical to that of a freshly prepared surface under UHV, indicating that there is no significant rearrangement of the Ni surface atoms. (C) 2004 Elsevier B.V. All rights reserved.