with capacitance C = 25 µF/cm 2 and the experimental Au(111) potential of zero charge U PZC = 0.5 V vs. SHE. We emphasize here (and for the remainder of this study) our reliance on a constant-charge approach which is only formally consistent with the true constantpotential picture in the thermodynamic limit of infinite cell size. There is good reason to expect this is a reasonable approximation in the present case, given the relatively low surface coverage in our simulations and low error estimates described in the SI, Section S3.