  The development of advanced electrochemical devices for energy conversion and
storage requires fine tuning of electrode reactions, which can be accomplished
by altering the electrode/solution interface structure. Particularly, in case
of an alkali-salt electrolyte the electric double layer (EDL) composition can
be managed by introducing organic cations (e.g. room temperature ionic liquid
cations) that may possess polar fragments. To explore this approach, we develop
a theoretical model predicting the efficient replacement of simple (alkali)
cations with dipolar (organic) ones within the EDL. For the typical values of
the molecular dipole moment ($2-4~D$) the effect manifests itself at the
surface charge densities higher than 30 $\mu C/cm^2$. We show that the
predicted behavior of the system is in qualitative agreement with the molecular
dynamics simulation results.
