Effect of orientational ordering of water dipoles on stratification of counterions of different size in multicomponent electrolyte solution near charged surface -- a mean field approach

TL;DR

This study uses a mean-field approach to analyze how water dipole orientation and ion size heterogeneity influence ion stratification, permittivity, and capacitance in the electric double layer near charged surfaces.

Contribution

It introduces a model incorporating non-uniform ion sizes and water dipole orientation effects into the analysis of electric double layers, extending previous models.

Findings

Water dipole orientation affects ion stratification.

Ion size heterogeneity influences permittivity and capacitance.

Bulk ion concentration impacts surface charge and counterion distribution.

Abstract

We theoretically studied electric double layer by using the mean-field approach including the non-uniform size effect and the orientational ordering of water dipoles in electrolyte solution. Performing the minimization of the free energy, the resulting ion and water distribution functions are determined numerically in the process of solving the Poisson's equation. The effect of non-uniform ionic size and orientational ordering of water dipoles on stratification of counterions of different size in multicomponent electrolyte solution near the charged surface are presented and discussed. Spatial dependence of relative permittivity and differential capacitance of electric double layer are also calculated for binary electrolyte solution and then compared with the predictions of the previous models. Effect of bulk concentration of counterions and ion size effects on surface charge density, excess portion of counterions, relative permittivity and differential capacitance are studied for multicomponent electrolyte solution in detail.