Cu─O─Al Interfacial Engineering on Cu Nanowires for Durable CO ₂ Electroreduction Into Multi‐Carbon Products

The balance between high selectivity and long-term stability for multi-carbon (C₂₊) production remains a critical challenge in CO₂ electrocatalysis due to competing reaction pathways and catalyst reconstruction under operating conditions. In this study, a core-shell heterostructure is synthesized by encapsulating copper nanowires (Cu NWs) with an aluminum oxide (AlOx) shell. Acting as a Lewis acid, the AlOx shell promotes charge redistribution to stabilize Cu⁺ species at the Cu─O─Al interface while creating an alkaline local microenvironment via ^*OH adsorption. These effects not only stabilize the catalyst structure but also preserve an optimal ^*CO intermediate coverage for efficient C─C coupling, as evidenced by in situ Raman spectroscopy and density functional theory (DFT) calculations. As a result, the system achieves a remarkable C₂₊ Faradaic efficiency (FE) of 69.6% at 600 mA cm^-2 in a flow-cell configuration. The stability tests further reveal a sustained FE_C2+ above 50% over 64 h of continuous operation at 300 mA cm^-2. Tuning of the AlOx shell crystallinity alters product distribution owing to different ^*OH adsorption capacities at the Cu─O─Al interface. These findings highlight the promise of AlOx encapsulation as a versatile strategy to simultaneously enhance selectivity and durability of Cu-based catalysts in the electrochemical CO₂ reduction reaction (eCO₂RR).