CARBON-MONOXIDE HYDROGENATION ON THE RU(001) SURFACE AT LOW-TEMPERATURE USING GAS-PHASE ATOMIC-HYDROGEN - SPECTROSCOPIC EVIDENCE FOR THE CARBONYL INSERTION MECHANISM ON A TRANSITION-METAL SURFACE

Hydrogenation of carbon monoxide on the Ru(001) surface has been inves tigated using high-resolution electron energy loss spectroscopy and te mperature-programmed desorption. Exposing gas-phase atomic hydrogen to a saturated carbon monoxide overlayer at 100 K results in reaction (v ia Eley-Rideal kinetics) under ultrahigh vacuum conditions. Both eta(1 )- and eta(2)-formyl are clearly identified as initial reaction produc ts at low atomic exposures. At higher exposures the production of eta( 2)-formaldehyde is observed. Annealing to 180 K decomposes some of the eta(1)-formyl, leading to adsorbed CO and hydrogen desorption, with t he remainder of the eta(1)-formyl converting to eta(2)-formyl. Upon an nealing to 220 K, the eta(2)-formaldehyde decomposes to adsorbed CO an d hydrogen which desorbs. Further annealing to 250 K leads to complete decomposition of the eta(2)-formyl, resulting in hydrogen desorption and regeneration of the original CO overlayer. These identifications r epresent the first spectroscopic observation of a carbonyl insertion c hannel operating during carbon monoxide hydrogenation on a well-charac terized transition metal surface.