Classical density functional analysis of the ionic size effects on the properties of charge regulating electric double layers

The focus of the present article is on the ionic size variation effects on the properties of charged interfaces involving electrolyte solution, commonly referred to as electric double layers. The presence of a well defined charged interface between the solution and a substrate has a profound impact on the local structure of the liquid phase. All solution species are distributed according to the various fluid and surface interactions. The excluded volume and finite dimensions of all ions and the solvent molecules are a major contributor to the detailed liquid structure. The structure determines important properties of the electric double layers such as charge and potential distributions and the surface and in the fluid. Our analysis is based on using classical density functional theory, which allows one to account for a variety of Coulombic and non-Coulombic interactions. The surface charge is determined by the thermodynamic equilibrium with potential determining species in the solution. We demonstrate that the size variation of the background electrolyte ions has a strong impact on the surface chemical equilibrium, as well as on the structure, charge and potential distributions in the electric double layer.