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

Abstract The balance between high selectivity and long‐term stability for multi‐carbon (C 2+ ) production remains a critical challenge in CO 2 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 C 2+ 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 CO 2 reduction reaction (eCO 2 RR).