HREELS STUDIES OF ETHANOL ADSORPTION AND DECOMPOSITION ON RH(100) SURFACE

The adsorption and decomposition of ethanol on the clean Rh(100) surfa ce were studied using thermal desorption spectroscopy(TDS) and high re solution electron energy loss spectroscopy (HREELS). At 130 K, on Rh(1 00) surface, the adsorption started from a chemisorbed ethanol structu re which was bonded to the surface through both O and H moieties, with the O-H bond almost parallel to the surfaces. Additional condensed ph ase of adsorbed ethanol was found to exist through hydrogen bonding. A t about 150 K, the multilayer-adsorbed ethanol desorbed from the surfa ces, while the remaining chemisorbed ethanol completely converted to a n ethoxy species via the first decomposition step in which O-H bond sc ission occurred. The small amount of methane formed indicated that the dehydrogenation of the ethoxide intermediates on the clean Rh(100) su rface was non-selective. Loss of hydrogen from the methylene group wou ld result in the formation of an aldehyde intermediate. Decarbonylatio n of the aldehyde intermediates produced methane and CO. This pathway appeared to be a minor one for ethoxide decomposition on Rh(100). The main ethoxide dehydrogenation proceeded via the cleavage of a C-H bond on the methyl group, resulting in the formation of an oxametallocycli c intermediate. The loss spectra at similar to 629 cm(-1) is assigned to this intermediate. The C-C bond scission occurred at the same time in the oxametallocyclic dehydrogenation sequence, Then the CO and hydr ocarbon moieties were formed on the surface.