A Gouy–Chapman–Stern model of the double layer at a (metal)/(ionic liquid) interface

Kornyshev [A.A. Kornyshev, J. Phys. Chem. B 111 (2007) 5545] has recently modelled the (metal)/(ionic liquid) junction and predicted therefrom the capacitance of that interface as a function of the applied potential. One of the purposes of the present article is to demonstrate that, at least in one particular case, the same prediction can be made more simply by applying the principles that Gouy, Chapman and Stern adopted in their classic treatments of the double layer at a (metal)/(electrolyte solution) interface. The analysis predicts the distributions of potential, charge and ionic concentration, leading to support of Kornyshev’s finding of a capacitance that displays a maximum value at the point of zero charge, whereas a minimum is expected for a double layer at an electrode in electrolyte solution. The two systems are compared and contrasted in respect to capacitance and the distribution of ions.