A HREELS study of C 1C 5 straight chain alcohols on clean and pre-oxidized Ag(110) surfaces

Abstract

High-resolution electron energy loss spectroscopy has been used to obtain vibrational spectra of the species produced by adsorption of the straight chain alcohols methanol through pentanol on clean and oxidized Ag(110) surfaces. As expected on the basis of previous work the alcohols are all found to adsorb reversibly on the clean Ag(110) surface and to form alkoxides on the pre-oxidized surface. In the case of methanol the formation of the alkoxide results in reorientation of the adsorbate such that the C-O bond axis tilts away from the surface resulting in a large increase in energy loss to excitation of the ν CO mode. For the longer chain alcohols formation of the alkoxide has a much less marked effect on the ν CO intensity. We have quantified this by determining I CO × n CH I CH for spectra of both the alcohols and the alkoxides to show that while the formation of meth methanol results in alignment of the CO bond away from the surface this does not occur during formation of alkoxides from the longer chain alcohols. As in the case of the alcohols, the alkoxides appear to be oriented with their alkyl chains parallel to the surface.