The adsorption, desorption, and reaction of methanol on oxygen-covered Rh(111) surfaces have been studied under ultrahigh vacuum (UHV) by using Auger electron, electron energy loss (in the electronic range), and thermal desorption spectroscopy. In the presence of oxygen adatoms the surface concentration of chemisorbed methanol increased, as indicated by the enhancement of the losses at 13.7-13.9 and 12.1-11 eV, and by the increased amount of decomposition products of chemisorbed species at higher temperature. It is proposed that the role of adsorbed oxygen is to promote the dissociative adsorption of CH3OH by forming a strong O-H bond which hinders the associative desorption of CH3OH. As a result, the surface concentration of irreversibly bonded methoxy species is increased. At the optimum oxygen coverage, θO ≈ 0.15-0.2, the number of methoxy species was twice that on clean Rh(111). Chemisorbed oxygen exerted a slight stabilizing effect on the methoxy species, which was stable up to about 200 K, but then decomposed and reacted with chemisorbed oxygen to yield H2, CO, H2O, and CO2.
|Number of pages||5|
|Journal||Journal of physical chemistry|
|Publication status||Published - Dec 1 1984|
ASJC Scopus subject areas
- Physical and Theoretical Chemistry