DFT calculations are performed within the VASP package using the RPBE exchangecorrelation functional and D3 dispersion correction scheme. Electronic states are described by the projector-augmented wave (PAW) method and a plane wave basis set with periodic boundary conditions. All calculations including O 2 are spin-polarized. We model the metal surface as a (non-symmetric) three-layer (3 × 4) supercell with two fixed bottom layers, while including a ca. 14 Å vacuum region between periodic images and applying a dipole correction 34 in the z-direction perpendicular to the surface. Full details on our DFT settings are found in the SI, Section S1.1. The applied saw-tooth potential (results of which are included in Figure