ETHYLENE HYDROGENATION ON NI(111) BY BULK HYDROGEN

We report that bulk H atoms, upon moving out from the bulk metal to the surface, readily hydrogenate ethylene adsorbed on Ni(111) to form ethane, while surface-bound H atoms have no hydrogenation activity. This result is the first observation of the role of bulk H specifically as a reactant in the hydrogenation of an unsaturated hydrocarbon on a transition metal and calls into question the generality of the Horiuti-Polanyi mechanism for catalytic hydrogenation reactions. This result is also a plausible molecular level basis for the correlation between the hydrogenation activity of a Raney Ni catalyst and the H content in the catalyst.