Adsorption of Polar Molecules onto Electrodes Driven By the Combined Effects of Dielectric Inhomogeneity and Electrostatic Correlation

A recent atomistic molecular dynamics simulation suggested that water molecules in ionic liquids are significantly adsorbed onto electrodes, but an understanding of this mechanism is limited. To clarify the simulation data, we highlight the effects of the dielectric contrast among the species by developing the mean-field theory that accounts for molecular polarization. We then demonstrate that polar molecules such as water may be enriched in the vicinity of electrodes and even markedly bound onto the charged surfaces when the electrostatic correlations are combined. Furthermore, we show that the energy efficiency may be improved through tuning the dielectric contrast within a certain range of the applied voltage.