Monovalent Ion Condensation at the Electrified Liquid/Liquid Interface

TL;DR

This study investigates monovalent ion condensation at an electrified water and organic solvent interface, revealing discrepancies with classical theory and demonstrating improved agreement with a modified Poisson-Boltzmann model.

Contribution

It introduces a non-monotonic ion-specific potential of mean force into the Poisson-Boltzmann framework, enhancing prediction accuracy for ion distributions at interfaces.

Findings

Standard Poisson-Boltzmann theory fails at high potentials.

Modified theory with ion-specific potential matches experimental data.

Ion condensation behavior depends on interfacial electric potential.

Abstract

X-ray reflectivity studies demonstrate the condensation of a monovalent ion at the electrified interface between electrolyte solutions of water and 1,2-dichloroethane. Predictions of the ion distributions by standard Poisson-Boltzmann (Gouy-Chapman) theory are inconsistent with these data at higher applied interfacial electric potentials. Calculations from a Poisson-Boltzmann equation that incorporates a non-monotonic ion-specific potential of mean force are in good agreement with the data.