ELECTROCHEMICAL DOUBLE-LAYER SIMULATIONS BY HALOGEN, ALKALI AND HYDROGEN COADSORPTION WITH WATER ON METAL-SURFACES

The experimental concept of simulating the metal-electrolyte interface by adsorption of solution components onto metal surfaces in UHV is briefly reviewed. Three coadsorption systems, involving electrochemically relevant ionic species interacting with water, are described to illustrate the detailed microscopic insight provided by this approach: (1) The electrostatic potential drop in the inner layer for specifically adsorbed chloride and bromide on Ag(110) is shown to be very similar in situ and in UHV. (2) A novel experimental concept for directly determining, at least formally, the dielectric constant of water in the double layer is exemplified by caesium-water coadsorption studies on Cu(110). (3) The recent contention that coadsorbed atomic hydrogen and water may react to form hydrated protons on Pt(111) has not been confirmed for Cu(110) by our TDS and EELS studies involving, for the first time, isotopic substitution of both adsorbates.