All calculations were carried out using the Vienna Ab initio Simulation Package (VASP) code and the projector-augmented wave (PAW) technique using the RPBE exchange-correlation functional. Constant voltage calculations were performed using the VASPsol implicit solvation method, assuming an SHE reference of -4.45 eV relative to the vacuum level . This approach implements an embedded polarizable dielectric continuum model that treats the ionic countercharge using a linearized Poisson-Boltzmann distribution. All calculations were performed using a dielectric constant of 80, a Debye length of 3 Å, and neglecting the cavitation energy contribution. All copper slab calculations were done using low-index copper surfaces of Cu (100), Cu (111) and Cu (211) with a vacuum region of 20 Å and a cutoff energy of 500 eV for planewaves. Slab sizes were 4x4x4 for Cu(100), 4x4x3 for Cu(111), and 6x3x4 for Cu(211). The free energies were determined using calculated electronic energies for all species, assuming adsorbate and gas phase entropic adjustments. Further details can be found in the Supplementary Material.