  We present a continuation of our theoretical research into the influence of
co-solvent polarizability on a differential capacitance of the electric double
layer [EPL 111, 28002 (2015)]. We formulate a modified Poisson-Boltzmann
theory, using the formalism of density functional approach on the level of
local density approximation taking into account the electrostatic interactions
of ions and co-solvent molecules as well as their excluded volume. We derive
the modified Poisson-Boltzmann equation, considering the three-component
symmetric lattice gas model as a reference system and minimizing the grand
thermodynamic potential with respect to the electrostatic potential. We apply
present modified Poisson-Boltzmann equation to the electric double layer
theory.
