Calculation of thermodynamic and inner layer characteristics of halide ions adsorbed on bismuth single crystal planes from solutions in methanol

The values of the surface excess and the Gibbs energy of adsorption of hali de ions on the (111), (001) and (01 (1) over bar) Bi single crystal planes in methanolic solutions have been calculated from the previously obtained e xperimental data using electrode potential as the independent electrical va riable. It was found that under comparable conditions the results obtained at constant electrode potential and at constant electrode charge are coinci dent. The electrosorption valency and the dipole moment of the dipole forme d by an adsorbed halide ion and its image charge in the Bi plane have been calculated. It was found that on the Bi(111) lane, where the chemical bonds are all saturated, the electrosorption valency does not depend on electrod e charge and in the measured range of potentials a weak, dependence of;he d ipole value formed by an adsorbed halide ion and its image charge in Bi on the electrode charge was found. In contrast, on the more active Bi planes t here is noticeable dependence of both characteristics on electrode charge a nd at higher positive charges, covalent bonding between Bi(01 (1) over bar) surface atoms and I- anions is probable. It was concluded that the dipole formed is screened significantly by the solvent molecules and the metal ele ctron gas. (C) 1999 Elsevier Science S.A. All rights reserved.