The unique chemistry of hydrogen beneath the surface: Catalytic hydrogenation of hydrocarbons

Hydrogen atoms emerging from the bulk of Ni metal to the surface are observ ed to be the reactive species in the hydrogenation of adsorbed methyl radic al, ethylene, and acetylene to gas-phase products. Surface-bound H atoms ar e unreactive. The distinctive chemistry of a bulk H atom arises largely fro m its significantly higher energy as compared to that of a surface-bound H atom. These results demonstrate that bulk H is not solely a source of surfa ce-bound H in catalytic hydrogenation as proposed 50 years ago, but rather, a reactant with a chemistry of its own.