UHV adsorption studies of K/H2O on Pt(111) and O/CH3COOH on Cu(110) : orientation and intermediates

Abstract Two model adsorption systems simulating an electrode/electrolyte interface are studied in UHV by high resolution electron energy loss spectroscopy (EELS) and X-ray photoemission spectroscopy, the latter also in the zero-order diffraction mode (XPD). Vibrational frequencies of molecular H 2 O coadsorbed with K on Pt(111) at a K coverage of 0.06 indicate the short range interaction between these species, a lack of H 2 O clustering and a substantial reorientation of the H 2 O molecule on the surface. At low H 2 O coverage, hydrogen bonding to the Pt surface is preferred over oxygen lone-pair bonding. The second investigation by XPD concerns the structure and orientation of adsorbed species, here products of acetic acid adsorption on Cu(110). Angular distributions of O 1s and C 1s core level electrons emitted from the adsorbed layer, show pronounced forward scattering peaks whose positions are indicative of an acetate species in bi-dendate configuration, with the O O axis aligned along the [11¯0] azimuth. The C C axis of acetate is perpendicular to the surface. On the other hand, some unexpected emission features, particularly an O 1s forward scattering peak normal to the surface, suggest the presence of additional intermediates on the Cu(110) surface. The data are supportive of acetic anhydride.