Crystal face effects on adsorption of ionic and non-ionic species on Ag electrodes: an electrochemical and STM study

The behaviour of the low-index faces of silver towards specific adsorption from aqueous solutions was investigated by measuring the adsorption of n-hexanol and tert-pentanol, which exemplifies the behaviour of physisorbed neutral compounds, the adsorption of bromide ions, which exemplifies the behaviour of chemisorbed ions, and the adsorption of uracil. STM images of specifically adsorbed bromide and iodide ions on Ag(111) were determined. The increase in the adsorptivity of the two aliphatic alcohols in the order Ag(110) <Ag(100) <Ag(111), i.e. in the order of decreasing hydrophilicity, is justified on the basis of a model of the Ag/electrolyte interface. The increase in the dipole moment associated with the adsorption of one bromide ion in the order Ag(111) <Ag(100) <Ag(110) is explained by a model of the adsorbed monolayer. The adsorption of uracil on Ag(111) is shown to proceed by diffusion control according to a Frumkin isotherm, followed by the nucleation and growth of a condensed two-dimensional phase.