Reversible Breathing of Cu─Co Dual-Atom Sites Enables Spatially Proximal C─N Coupling for Urea Electrosynthesis

Electrocatalytic urea synthesis via the Langmuir-Hinshelwood pathway demands spatially proximal active sites to synchronize the generation and cross-coupling of C- and N-derived intermediates. Heteronuclear dual-atom catalysts offer chemically differentiated sites for this purpose, yet whether their bimetallic centers remain static or dynamically evolve during C─N coupling remains unresolved. Here, we construct a well-defined N₃─Cu─Co─N₃ dual-atom site for the electrochemical coreduction of CO₂ and NO₃ ^- to synthesize urea and uncover its reversible, electric-field-driven structural breathing under electrocatalytic conditions, affording a maximum urea yield rate of 4828.4 ± 136.5 µg h^-1 mg_cat ^-1 and a Faradaic efficiency of 56.8 ± 7.6% at -1.2 V (vs. RHE). Operando x-ray absorption spectroscopy (XAS) revealed a reversible, electric-field-driven breathing-like modulation of the Cu─Co distance, characterized by Cu─Co contraction and Cu─N/Co─N elongation. Density functional theory (DFT) calculations show that the Cu─Co distance reaches a minimum of 2.16 Å in the *CONH₂-bound configuration formed during the initial C─N coupling step. The adaptive contraction brings C- and N-intermediates into close proximity to enable C─N coupling, thereby reconfiguring heteronuclear dual-atom sites from static pairs into dynamically responsive centers and highlighting field-tunable metal-metal distance as a catalytic design lever.