While the formation of dissolved Cu(OH)2 complexes appears feasible under the studied applied potentials, this dissolution route does not require the presence of CO2, which suggests other pathways for Cu dissolution must be contributing under CO2 ER conditions based on the experimental observations. For applied potentials below the onset of CO2 reduction, CO2 binding can result in OCHO* intermediates on Cu , while CO2 binding on oxidized copper surfaces can lead to the presence of CO3 and HCO3-like bound intermediates . The dissolution of Cu via these types of complexes are included in Figure , panels b-d, in Figure and in the Supplementary Material, where we find that at studied pH and applied potential ranges, complexes with OCHO and OH exhibit the most reducing dissolution potentials. For example, we calculate dissolution potentials of -0.54 V vs SHE (-0.13 vs RHE) on Cu (211) step edges with the formation of Cu-OCHO-OH complexes (Figure ). We also find that Cu-2CO3, Cu-HCO3-OH, and Cu-HCO3-CO3 complexes can also facilitate surface degradation at less reducing potentials (see Figure ), but these generally require higher pHs than accessed in our in situ measurements. Nonetheless, our calculated values indicate that a number of these complexes can thermodynamically initiate surface degradation in the range of electrochemical potential values tested experimentally in this study. The detrimental role of OCHO* in dissolution is consistent with experiments performed at near-neutral pH values, the presence of CO2 in solution, and low reducing potentials before CO2 ER is initiated. We also expect that the thermodynamic dissolution potentials to be lower for nanoparticles with higher surface roughness that contain undercoordinated copper atoms at defect, kink, or edge sites.