Engineering an Ordered Intermediate Phase between Disordered Phases for CO 2 Reduction to Multicarbon Products

Electrochemical CO2 reduction (CO2RR) to multicarbon (C2) products provides a compelling pathway for carbon recycling and sustainable energy storage, yet achieving high C2 selectivity remains a major challenge due to kinetic preference for C1 products and the intrinsic difficulty of C–C bond formation. While bimetallic alloys are widely used to tune catalytic performance, their typically random atomic arrangements hinder precise control over active site electronic environments, leading to suboptimal C1/C2 selectivity. Herein, we present a composition-dependent phase engineering strategy to synthesize ordered Au1Cu1 intermetallic alloy, alongside disordered Au3Cu1 and Au1Cu3 alloys, via a polymer nanofiber-mediated approach. The long-range atomic ordering in Au1Cu1 enables an optimized d-band center, critically balancing intermediate binding (e.g., *CO at −1.09 eV) for efficient C–C coupling over C1 formation. This resulted in the Au1Cu1/CNFs catalyst reaching a peak Faradaic efficiency of 55.6% toward C2 products at −0.5 V vs RHE. In situ characterizations and theoretical calculations confirm that its specific electronic and geometric configurations facilitate the lowest energy barrier for *CHO–*CO coupling. This work demonstrates precise atomic-level control in bimetallic alloy ordering, guiding the CO2RR toward valuable multicarbon products.