Solid Solution In Situ‐Reconstructed Mg‐Cu ₂ O/Cu Heterointerface for CO ₂ Reduction to C ₂₊ Alcohols in Neutral and Acidic Media

ABSTRACT Electrochemical CO 2 reduction presents a sustainable route for producing value‐added liquid C 2+ alcohols. Using neutral and acidic media enables high CO 2 utilization, but suffers low C 2+ alcohols selectivity and production rate, due to high energy barrier of C─C coupling and competing C 2 H 4 pathway on conventional Cu catalysts. Herein, we report porous Mg‐stabilized Cu 2 O/metallic Cu (Mg‐Cu 2 O/Cu) heterointerface, in situ reconstructed from block copolymer‐derived mesoporous MgCuO solid solution under operating CO 2 reduction conditions, that realizes extraordinary neutral and acidic CO 2 ‐to‐C 2+ alcohols performance. In situ spectroscopic and computational investigations disclose that Mg‐Cu 2 O/Cu heterointerface facilitates *CO hydrogenation and triggers energy‐favorable asymmetric *CO─CHO coupling, distinctive to energy‐intensive symmetric *CO─CO dimerization catalyzed by bare CuO‐derived Cu surface. More importantly, the heterostructure modulates bonding strength of key C 2+ intermediate with enhanced O─C yet weakened Cu─O bonds, switching selectivity from C 2 H 4 on Cu to C 2+ alcohols on Mg‐Cu 2 O/Cu. Along with porous architecture affording abundant accessible sites, we achieve remarkable Faradaic efficiencies of 70.4% at an industrial current density of 448.7 mA cm −2 in neutral electrolyte and 61.4% at 316.1 mA cm −2 in acid for C 2+ alcohols, placing among the highest levels reported hitherto. This work provides a general catalyst design framework for steering reaction pathways in practical CO 2 electrolysis.