Notably, the PMFs with explicit and implicit carbon deviate significantly in the CIP regime, with the implicit model predicting a more stable CIP by 2.0 k B T . We propose that this discrepancy arises from differences in the electronic structure of the confining materials: graphene is a semi-metal, while the implicit confining potential has the dielectric constant of vacuum. The electronic properties of the wall determine the extent to which the surface polarizes in response to a nearby ion; this polarization then modifies the electric field generated by the ion. Qualitatively, we can interpret the effect of surface polarization in these systems in terms of image charges. A single ion of charge q near a solid interface will generate an image charge q ′ whose sign and magnitude depend on the dielectric constants (ϵ) of the electrolyte and wall: 50 q ′ = -(ϵ wall -ϵ electrolyte )(ϵ wall + ϵ electrolyte )q. Thus, an ion confined by a metallic surface will generate an image charge of the opposite sign, decreasing the resulting electric field and thereby reducing the ion's propensity for pairing. The impact of a confining surface's electronic structure on Coulombic interactions has been modeled at a continuum level by Kavokine et al., where the authors quantify the increase in electrostatic 11 energy of a confined ion as the Thomas-Fermi screening length decreases. These authors' findings are consistent with the results shown in Fig. where an insulating confining wall yields more contact ion pairing than the explicit graphene.