Theoretical Prediction of the Capacitance of Ionic Liquid Films

We use classical density functional theory to investigate ionic liquid + solvent mixtures against smooth, model electrodes. We consider those mixtures that display a wetting transition at the electrodes. We find that a wetting film of an ionic liquid at the electrodes has similar properties to the neat liquid. A novel aspect of this transition is that, close to a surface critical point, we find an extraordinary increase in the capacitance, which is derived from the critical behavior.