Restructuring of the electrical double layer in ionic liquids upon charging

We have investigated the electrical double layer (EDL) structure in ionic liquids using molecular dynamics simulations with three different models of ionic liquids.We show that the EDL restructuring, driven by surface charging, can be rationalized by use of two parameters, renormalized surface charge (κ) and charge excess in interfacial layers (λ).Analysis of relationships between the λ and κ parameters provides new insights into mechanisms of over-screening and charge-driven structural transitions in the EDL in ionic liquids.We show that the restructuring of the EDL upon charging in all three studied systems has two characteristic regimes: (1) Transition from the bulk-like (κIon = 0) to the multilayer structure (κIon ≈ 0.5) through the formation of the commensurate multilayer of counter-and co-ions; and(2) Transition from the multilayer (κIon ≈ 0.5) to the crowded (κIon > 1) structure through the formation of a monolayer of counter-ions at κIon ≈ 1.0.