UHV ADSORPTION STUDIES OF K/H2O ON PT(111) AND O/CH3COOH ON CU(110) - ORIENTATION AND INTERMEDIATES

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 H2O coadsorbed with K on Pt(111) at a K coverage of 0.06 indicate the short range interaction between these species, a lack of H2O clustering and a substantial reorientation of the H2O molecule on the surface. At low H2O 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 O1s and C1s 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 [1(1) over bar0$] azimuth. The C-C axis of acetate is perpendicular to the surface. On the other hand, some unexpected emission features, particularly an O1s 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.