General theory of charge regulation and surface capacitance

TL;DR

This paper develops a generalized mean-field theory for charge regulation and surface capacitance, incorporating non-electrostatic effects and providing thermodynamic insights into ion-surface interactions and differential capacitance.

Contribution

It introduces a comprehensive approach that accounts for ion-ion and ion-surface non-electrostatic effects on equal footing, advancing understanding of surface charge regulation.

Findings

Surface adsorbed ions influence packing more than bulk constraints.

The model explains differential capacitance behavior in various ion-surface interaction scenarios.

Packing considerations are crucial before bulk packing constraints become relevant.

Abstract

A generalization of the mean-field approach will be derived that will take into account the ion-ion as well as ion-surface non-electrostatic effects on an equal footing, being based on the bulk and surface equations of state in the absence of electrostatic interactions. This approach will be applied to the calculation of the differential capacitance for several models of the specific ion-surface non-electrostatic interactions providing a thermodynamic insight into the characteristics of the differential capacitance. The packing considerations due to surface adsorbed ions will be shown to be more relevant then the bulk packing constraints for ions vicinal to the surface, and to set in prior to the conditions where the bulk packing constraints would become relevant.