Electrochemical hydration and reaction processes on metal surfaces studied by gas phase adsorption

The distinction between surface hydration and reaction processes in ultrahigh vacuum studies of electrochemical phenomena is illustrated by coadsorption of H2O with: (i) Cs on Cu(110); at low caesium coverages, solvation of the adsorbed alkali is observed and above a critical coverage of θCs = 0.15 a surface reaction occurs forming hydroxide and hydrogen. Work function measurements have also been used to characterize the dielectric screening by interfacial water; (ii) hydrogen on Cu(110) and Pt(111): TDS and HREELS measurements using isotopic substitution of hydrogen by deuterium have been used to investigate the formation of (H3O+)ad. Whereas on Cu(110) hydrogen is merely solvated by water, on Pt(111) there is evidence for the production of hydrated protons