• • Cu reconstruction in CO2RR requires Cu+ species generated from HCO3−-mediated ·OH radicals; in HCO3−-free acidified K2SO4 electrolyte, reconstruction is minimal, indicating that oxidative dissolution-redeposition dominates only under neutral/alkaline conditions. This dictates electrolyte selection for stable CO2RR operation.
• • CORR-induced reconstruction proceeds independently of Cu+ and ·OH, with potential-induced atomic migration as the sole mechanism; this enables reconstruction even in HCO3−-free electrolytes, simplifying electrolyte management for CORR.
• • DFT calculations show that adsorbed *CO weakens Cu–Cu bonds, creating metastable surface configurations that lower the activation barrier for atomic migration; this explains why CORR, which produces high *CO coverage, promotes migration-driven reconstruction.
• • In situ AFM and DFT results across varying potentials confirm that applied potential promotes both mechanisms, with the balance shifting from dissolution-redeposition to atomic migration as potential increases; this provides a unified framework for predicting reconstruction under operational conditions.