unit cell was used to represent each metal surface, corresponding to a surface coverage of 1/9 monolayer (ML). The adsorbates and the two topmost layers were allowed to relax, while the remaining layers were constrained. A plane wave energy cutoff of 400 eV was used with a 4 X 4 X 1 k-point set for all surfaces. Slabs are separated in the z direction with a vacuum spacing of 17 Å. Spin polarization and Methfessel-Paxton scheme with energy smearing of 0.2 eV were applied for all calculations. Dipole corrections were included in the z direction to cancel out the net dipole moment on the surface and simulate the charge placed on the surface in electrochemical environment. Magnetic moment correction was applied for those metals that are ferromagnetic (Ni, Fe, Co).