Figure 6 . (a) Surface voltage as a function of surface charge
density; and (b) the capacitance of nanoslit versus the surface charge
density, predicted through the CDFT in comparison with the simulation
reported by GoĢrniak et al.59
By using the MDFT in combination with the critical structural
orientation = 0.68, we first calculate the solvation diameters of ions
in confined MeCN within the nanoslits with different pore widths. Here,
the anion of BF4- is considered which
is modeled as a LJ particle carrying one elementary charge. The LJ
parameters are presented in the SI with the size of bare ion = 0.33 nm.Figure 7 (a) shows the dependence of the predicted solvation
diameter versus the pore width of
nanoslit,i.e ., . The solvation diameter varies along the pore width,
displaying an oscillative decline when reducing the pore
width.
By incorporating the ion solvation diameter into the
solvation-diameter-dependent coarse-grained model, and assuming that the
cation and anion have equal size, the capacitances of the nanoslits
involving MeCN-based electrolyte with different pore widths are
calculated through CDFT, as shown in Figure 7 (b) . Here, the
bulk ion concentration = 1.50 M and the other system parameters are the
same as those in Figure 5 . For comparison, the capacitances
without considering ion desolvation are calculated as well, in which all
parameters are the same except that a uniform ion size is adopted as =
0.73 nm corresponding to the solvation diameter of
BF4- in bulk MeCN. Conventionally, the
ion solvation diameter in bulk solution has been employed in theoretical
calculation.60