Methane activation on Ni(111):: Effects of poisons and step defects

We have, theoretically and experimentally, investigated the dissociation of methane on the terraces and steps of a Ni(1 11) surface. Using Density Functional Theory (DFT) total energy calculations combined with Ultra High Vacuum (UHV) experiments, we find that the steps exhibit a higher activity than the terraces. We have, furthermore, investigated how carbon and sulfur present on the surface will deactivate the steps, leaving only the terraces active. We find the intrinsic sticking probabilities of methane on the steps and terraces at 500 K to be 2.8 x 10(-7) for the steps and 2.1 x 10(-9) for the terraces, in complete agreement with our calculated difference in activation energy of 17 kJ/mol. (c) 2005 Elsevier B.V. All rights reserved.