Disrupted CO Migration and Reversed Activity in CuAg Spatiotemporal Tandem Catalysts for C ₂₊ Production

Rational catalyst architecture is essential for driving the electrochemical CO 2 reduction toward multi‐carbon (C 2+ ) products; however, many previously reported strategies rely on intricate structural designs that hinder large‐scale implementation. Herein, we establish a simplified yet highly efficient tandem catalyst strategy for driving electrocatalytic CO 2 reduction toward multi‐carbon products. By systematically dissecting the influence of Cu–Ag spatial arrangement and interfacial engineering, we demonstrate that the effectiveness of tandem catalysis is governed primarily by two key factors: the continuity of CO transport pathways and the accessibility of CC coupling sites. Reversed Cu–Ag configurations and carbon interlayers hinder intermediate delivery, suppressing C 2+ formation, whereas a directly coupled Cu–Ag interface enables rapid CO generation, migration, and subsequent CC coupling. This optimized configuration achieves a high C 2+ Faradaic efficiency of 75% at industrially relevant current densities (250 mA cm −2 ) while maintaining stable operation for over 45 h. Our findings not only advance the fundamental understanding of intermediate management in tandem catalytic systems but also provide practical design principles for constructing scalable CO 2 electrolyzers.