Recognizing the Universality of Copper Reconstruction Via Dissolution-Redeposition at the Onset of CO₂ Reduction

The electrochemical CO₂ reduction (ECO₂R) on copper (Cu) remains one of the most promising pathways to convert CO₂ into value-added products. However, it suffers from severe restructuring, resulting in the unknown structural identity of the ECO₂R active catalyst. Here, we show that dissolution-redeposition is the universal early-stage restructuring mechanism in ECO₂R, occurring across all the tested Cu morphologies, including foils, nanoparticles, oxide-derived films, and gas diffusion electrodes. Using identical location scanning electron microscopy, we directly visualize and confirm that this transformation begins at the reaction onset, reshaping catalyst morphology and complicating structure-activity interpretations. Our findings demonstrate that all the Cu catalysts act as precursors to their true, in situ-formed active phase, generated through the reduction of Cu oxides and electrolyte-driven dissolution-redeposition. Recognizing the universality of this transformation is essential for accurate mechanistic understanding and the rational design of future Cu-based ECO₂R catalysts.