P. Nikitas, A NEW APPROACH TO DEVELOPMENT OF IONIC ISOTHERMS OF SPECIFIC ADSORPTION IN THE ELECTRICAL DOUBLE-LAYER, Journal of physical chemistry, 98(26), 1994, pp. 6577-6585
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.