Engineering an Ordered Intermediate Phase between Disordered Phases for CO₂ 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.