Simulations of solvent effects on confined electrolytes

Abstract

Monte Carlo simulations are reported for the solvent primitive model (SPM) of the electrical double layer at electrically charged and neutral surfaces. Both solvent and ions are modeled as hard spheres with interactions governed by hard sphere and Coulomb interactions. Density profiles of solvent and ions and electrostatic potential profiles are presented for 1:1 electrolyte concentrations of 1 and 2 M at 300 K. Comparison of results at charged and neutral walls indicates that the density distribution of a dense solvent near a wall induces significant layering of ions and decrease of potentials in the double layer. This layering effect cannot be captured in simulations of the conventional primitive model (PM) of the double layer. The solvent induced steric ordering of electrolyte ions at a neutral wall can create a space charge layer.

Monte Carlo study of the electrode|solvent primitive model electrolyte interface

“…The electric charge of the electrode repels the cations, while the solvent molecules support their adsorption. The qualitatively similar behaviour of the cations in the vicinity of the electrode was predicted by the DFT [16,20] and MPB [23] theories and also by the earlier MC simulation [22,24]. Consideration of the realistic model of water changes this picture.…”

“…The DFT theory has also been applied by other authors [17][18][19][20][21]. The first reliable but scattered Monte Carlo (MC) results were published by Zhang et al [22]. Lamperski et al [23] showed that the modified Poisson-Boltzmann (MPB) extension to solvent molecules was in reasonable agreement with these MC results.…”

Wetting and drying scenarios of ionic solutions

“…[15] on the basis of a free energy functional detailed below including an approximate Coulomb correlation term [35], for NaCl, KCl and CaCl 2 . For the monovalent ion cases and moderate surface charges σ the correlation term does not significantly modify the predictions based on the mean-field density functional, which yields density profiles in reasonable agreement with Monte Carlo data for a symmetric SPM [15,36].…”

“…For a given ε(z) Poisson's equation ( 36) was solved numerically by a Runge-Kutta method, subject to the boundary conditions: The equilibrium density profiles are determined by minimizing the grand potential per unit area:…”

Charge neutrality breakdown in confined aqueous electrolytes: Theory and simulation

“…It is usual to take for granted the local charge neutrality between charged surfaces [43][44][45] when dealing with EDL in both theoretical and computational approaches. This is not to be confused with the overall charge neutrality, which clearly has to be always satisfied for a charged system as whole.…”