As apparent from Fig. , at nominally identical bias charge, FF-PCH simulations exhibit a significantly larger electrostatic potential drop ∆ϕ bias as compared to the DFT simulations. This evidently originates from the strong confinement of excess electrons within the electrode in the FF case, whereas a sizable elec- tron spillover into the interfacial water region is observed in the DFT simulations. An extended, comparative analysis as in Fig. for all simulated bias charges can be found in Fig. of the SI.