A NEW APPROACH TO DEVELOPMENT OF IONIC ISOTHERMS OF SPECIFIC ADSORPTION IN THE ELECTRICAL DOUBLE-LAYER

A new approach, which combines classical thermodynamics with basic ele ctrostatic arguments, is proposed for the development of new ionic iso therms of specific adsorption on ideally polarized electrode surfaces. The main features of this approach are the following. The inner layer is considered to consist of two zones, along which the electric field is homogeneous. Then the Gauss theorem of electrostatics is used to C orrelate the potential drop across the inner layer with the electrode charge density. This correlation allows the derivation of the electroc hemical potentials of the constituents of the inner layer based exclus ively on the properties of certain thermodynamic functions of this lay er. The adsorption isotherms, which arise from the electrochemical pot entials, can take into account changes in the dielectric constant, the inner layer thickness, and the orientation of the solvent dipoles dur ing the adsorption process. Comparison with experiment shows that even the simplest isotherm, which takes into account only variations of th e dielectric constant, can give an almost quantitative description of experimental isotherms.