An Improved Approximation for the Primitive Model of the Electric Double Layer

Abstract

The primitive model for the one sided electrode interface consists of an electrode which is perfectly smooth and flat, and an electrolyte formed by charged hard spheres, all immersed in a dielectric continuum.

The early work of Gouy,¹ Chapman² and Stern³ is based on such a model, and in recent times it has received considerable attention by a number of researchers. Extensive computer simulations have been performed by Torrie, Valleau and coworkers.⁴ The approximate integral equations which have been used to compute the density and voltage profiles and differential capacitance can be divided into four groups. Mean Spherical Approximation (MSA) and its generalization (GMSA),^5,6 the Hypernetted Chain (HNC) and derived equations,^7,8 the Modified Poisson-Boltzmann's (MPB)⁹ and the Born-Green-Yvon (BGY)^10,11 type theories.