Fig. 9.

Model results: (A) water adsorption + ion attraction [model by Le et al. (19) combined with model from ref. 7]; (B) ion attraction only (model from ref. 7); and (C) water adsorption without ion attraction (model by Le et al. only). All figures are obtained assuming an equal hydrated ion size for the cation and the anion. The parameters for the mean-field model with ion–surface attraction are similar to those in figure 8 in ref. 7 with $x_{\mathit{rep}}\approx 3$ Å and ${\epsilon }_r$ ramped from 4 to 80 in the interval [1.8,2.3] Å to match the model by Le et al. Hydrogen and the hydroxide adsorption are not considered in this model; the observed increase of (pseudo)capacitance at low and high potentials (see Fig. 1) is thus not captured.