The reaction of CO and H2to produce CH4has been studied at high pressures over Ni(100) and Ni(111) surfaces using a microcatalytic reactor system and Auger Spectroscopy. It has been found that theratepersurfaceNiatomis identical on the two crystal planes and is very similar to the specific rate on high area supported Ni catalysts. In addition, the activation energy is independent of Ni catalyst structure. Auger spectroscopy has been used to characterize the surface carbon produced by CO decomposition on Ni, and it is concluded that a carbidic form of carbon is an intermediate in the catalytic synthesis of CH4over Ni.