For the liquid electrolyte case, a 50 µm diffusion layer including M + , CO 2 , HCO - 3 , CO 2- 3 , H + , and OH -was modeled, including bulk reactivity, diffusion, migration, and steric exclusion term . The model is commonly referred to as gmPNP (generalized modified Poisson-Nernst-Planck). We considered a set of CO 2 -saturated carbonate solutions with Li + , K + , and Cs + as counterions. We assumed that the carbonates dissociate completely and that the various cations do not behave as Lewis acids. The species concentration bulk boundary conditions, as well as the initial conditions, correspond to the bulk concentration of all species calculated for a given initial buffer concentration considering homogeneous equilibria, Sechenov's coefficients to account for the ionic strength of the initial buffer and Henry's law to calculate the CO 2 solubility. Bulk concentrations for all species for the K + case are given in Table . The bulk potential is at the point of zero charge (PZC). PZC values for different levels are given in Table .