Selective cation depletion from an ionic liquid droplet under an electric field

•The dynamics of IL droplet under an electric field are analyzed via MD simulations.•The mechanism of a selective cation depletion is phenomenally explained.•The intermolecular interaction is a key parameter for a selective cation depletion.

We conducted MD simulation to investigate the general electrohydrodynamic behavior of droplets of imidazolium-based ionic liquids composed of 1-ethyl-3-methylimidazolium (EMIM) anion and either bis(trifluoromethylsulfonyl)imide (NTf2) or ethylsulfate (ES) cation. The cation depletion phenomena observed in the previous work [J. Phys. Chem. Lett. 5 3021 (2014)] is analyzed in detail to clarify its mechanism. Shape deformation due to electric stress and the ion distributions inside the droplet are calculated with 200 ion pairs and the intermolecular interactions between ions are directly analyzed. Together with an analytical interpretation of the conducting droplet in an electric field, we show that the MD simulation successfully explains the mechanism of selective ion depletion of an ionic liquid droplet in an electric field, and the retreating motion of the droplet observed by experiments.