Hydrogenation of carbon monoxide on Ni(1 1 1) 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 H2 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 °C approximately, a Ni3C epitaxial film develops on the surface and no methane production occurs. At temperatures above 400 °C, 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.