Theory of electrode polarization: application to parallel plate cell dielectric spectroscopy experiments C. Chassagne a, *, D. Bedeaux a , J.P.M. van der Ploeg a , G.J.M. Koper b a Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands b Laboratory of Physical Chemistry, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands Abstract An extension of the model for electrode polarization of Cirkel et al. [Physica A 235 (1997) 269] is given. The problem is solved using both classical boundary conditions and the new boundary conditions using excess densities presented in a previous paper [J. Phys. Chem. B 105 (2001) 11743]. In the present paper, the electrodes are supposed to be ideal, meaning that charge transfer or adsorption are not considered. The advantage of the new boundary conditions lies in the possibility to extend to more complicated situations including for instance specific ion adsorption. We prove that the new boundary conditions and classical ones give the same results. A comparison of the model predictions, involving no adjustable parameters, experimental dielectric spectroscopy data is performed and fairly good agreement is found. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Electrode; Polarization; Adsorption 1. Introduction Electrode polarization is a phenomenon that hampers dielectric spectroscopy measurements of many systems such as dispersions, microemulsions or polymer solutions at low frequencies due to the presence of electrolyte. As in most of these systems the relaxation frequencies and permittivity en- hancements are located in these low frequency regimes, it is important to compensate for this phenomenon. Various authors proposed empirical models involving equivalent circuits [1 /3] to account for electrode polarization. Considering the behavior of ions under the influence of an alternating electric field, we derive here an analytical expression for the complex permittivity due to electrode polarization. Such an analytical expression has already been pre- sented for the case of a symmetric electrolyte and planar electrodes [4]. In the present paper, this theory will be extended to the case of asymmetric electrolytes. We will also derive the equations using the new boundary conditions that were introduced for the calculation of the dielectric permittivity of spherical particles [5]. These new boundary conditions are based on the concept of excess quantities in the sense of Gibbs introduced by Albano et al. [6,7]. The advantage of the new * Corresponding author. Tel.:  /31-71-527-4560; fax:  /31- 71-527-4239 E-mail address: chassagn@chem.leidenuniv.nl (C. Chassagne). Colloids and Surfaces A: Physicochem. Eng. Aspects 210 (2002) 137  /145 www.elsevier.com/locate/colsurfa 0927-7757/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0927-7757(02)00379-5