Solvent primitive model of an electric double layer in slit-like pores: microscopic structure, adsorption and capacitance from a density functional approach

TL;DR

This paper uses a density functional approach to study the microscopic structure, adsorption, and capacitance of an electric double layer in slit-like pores within a solvent primitive model, highlighting the effects of voltage and pore width.

Contribution

It introduces a density functional method to analyze the electric double layer in a solvent primitive model, extending previous primitive model studies by including solvent effects.

Findings

Differential capacitance exhibits a camel-like shape at low ion fractions.

Capacitance dependence on pore width is oscillatory.

Results are similar to those of the primitive model without solvent.

Abstract

We investigate the electric double layer formed between charged walls of a slit-like pore and a solvent primitive model (SPM) for electrolyte solution. The recently developed version of the weighted density functional approach for electrostatic interparticle interaction is applied to the study of the density profiles, adsorption and selectivity of adsorption of ions and solvent species. Our principal focus, however, is in the dependence of differential capacitance on the applied voltage, on the electrode and on the pore width. We discuss the properties of the model with respect to the behavior of a primitive model, i.e., in the absence of a hard-sphere solvent. We observed that the differential capacitance of the SPM on the applied electrostatic potential has the camel-like shape unless the ion fraction is high. Moreover, it is documented that the dependence of differential capacitance of the SPM on the pore width is oscillatory, which is in close similarity to the primitive model.