Cu degradation susceptibility was estimated by calculating the thermodynamic driving force for electrodissolution under varying electrochemical conditions. The potential-dependent copper vacancy formation energies and the corresponding copper dissolution potentials are summarized in Figure for the most favorable of the studied set of solvated copper complexes, which include various combinations of OH, CO3, HCO3, CO2, OCHO, and H2O ligands as detailed in the Supplementary Material. The vacancy formation energies correlate with the site coordination number, with VCu predicted to form more easily on lower coordinated binding sites such as step edges on the (211) surfaces over highercoordinated sites like on (100) and (111) terraces. The solvated copper complexes with one or more hydroxide ligands are generally found to be the most favorable, exhibiting the largest thermodynamic driving force toward forming surface vacancies and facilitating degradation on the copper surface. As seen in Figure , Cu(OH)2 formation has calculated dissolution potentials that are -1.02 V vs SHE (-0.61 V vs RHE) for Cu(211) step edges and ~0.3-0.5 V higher on terraces, indicating that Cu dissolution is thermodynamically favorable under modestly reducing potentials consistent with CO2 ER. We note that these dissolution potentials also depend on pH, the ionic strength, and the concentration of Cu in solution ([Cu]), which can further alter the specific potential values at which Cu dissolution is expected to become thermodynamically preferable. In Figure we include the pH dependence of the most favorable complexes for each Cu facet, all assuming the same [Cu] as in Figure .