A density functional theory study of electric potential saturation: planar geometry

We investigate the possibility of electrostatic potential saturation, which may lead to the phenomenon of effective charge saturation. The system under study is a uniformly charged infinite plane immersed in an arbitrary electrolyte made up of several micro-species. To describe the electric double layer, we use a generic density functional theory in which the local micro-ionic density profiles are arbitrary functions of the local electrostatic potential. A necessary and sufficient condition is obtained for saturation, whereby the electrostatic potential created by the plane becomes independent of its bare charge, provided the latter is large enough.