Pulsed Electrolysis Yields Dynamically Stable Active Copper Sites for Selective CO2 Reduction via Dissolution–Redeposition

Pulsed electrolysis enhances the stability of electrochemical CO2 reduction (ECO2R) on copper, but the mechanistic origin of this effect remains unclear. Using identical location electron microscopy and operando impedance spectroscopy, we show that pulsed operation dynamically restructures the morphology of the copper surface. Over 23 hours, the catalyst evolved from its initial state into a grain-like architecture with dendritic features, accompanied by a steady increase in the ethylene-to-hydrogen ratio. This correlation identifies the dissolution–redeposition of copper as the central mechanistic pathway through which pulsing governs ECO2R stability.