Hydrogenation and H, D Exchange studies of ethylidyne (CCH3) on Rh(111) crystal surfaces at 1 atm pressure using high resolution electron energy loss spectroscopy

We have combined high resolution electron energy loss spectroscopy (HREELS) with a high-pressure/low-pressure (HPLP) system to study the behavior of the monolayer structure of stable hydrocarbon species that form on single-crystal metal surfaces during catalytic reactions at atmospheric pressure. We find that a monolayer of adsorbed ethylidyne (CCH3) on Rh(111) at 310 K does not hydrogenate to ethylene or ethane in one atmosphere of static D2. The methyl group hydrogens exchange with deuterium is a slow process. The amount of exchange depends strongly on the amount of uncovered, bare-metal surface, but little on the hydrogen pressure. A mechanism for H, D exchange involving ethylidene (CHCH3) as an intermediate is proposed.