Finally, using the calculations performed outside the PZC, we calculated differential capacitance values for the three models on both the clean surface and with adsorbed oxy-gens. The higher capacitances predicted by the RISM models are in good agreement with experimental studies, and the decrease in capacitance with oxygen coverage is correctly identified. Nevertheless, we mention an important drawback of the method with the presence of important Fermi energy fluctuations and computational instability which do not allow us to calculate differential capacitances accurately over the entire range of potentials.