Restricting Copper Reconstruction with Ultrathin Polydopamine for Selective and Stable Electrochemical CO ₂ Reduction Reaction to C ₂ Products

A strategy is presented to mitigate copper surface reconstruction during electrochemical CO 2 reduction reaction (EC‐CO 2 RR) by conformally coating copper microcubes (CuMCs) with an ultrathin (≈2 nm) polydopamine (PDA) layer. The formation of nanocubes (30–50 nm in size) at the surface of microcubes at the early stages of the EC‐CO 2 RR contributes to suppressed surface reconstruction and sustained Faradaic efficiency (FE) for C 2 products. Furthermore, PDA coating effectively stabilizes adsorbed CO atop and CO bridge intermediates and promotes CC coupling. As a result, the FE for C 2 products increases from 52.0 ± 4.0% for unmodified CuMCs to 81.6 ± 2.8% for PDA‐coated CuMCs at −1.18 V versus reversible hydrogen electrode (V RHE ). The PDA coating effectively slows down the surface evolution process of the catalyst during electrolysis. After 18 h of continuous operation at −0.88 V RHE , the CuMCs retain their original framework owing to a tightly adhered PDA layer that effectively stabilizes the surface and enhances catalyst durability. In situ surface‐enhanced infrared absorption spectroscopy confirms the presence of adsorbed CO atop , CO bridge , and OCCOH intermediates on PDA/CuMCs surface, which are believed to boost CC coupling. This work highlights the potential of polymer film to stabilize the catalyst surface and steer product distribution in CO 2 electroreduction.