Engineering Cu/Cu+ interfaces to boost C–N coulping for urea electrosynthesis: from fundamental insights to efficient catalysis

Efficient electrocatalytic C–N coupling for urea production requires the development of high-performance catalysts and a fundamental understanding of their reaction mechanisms. However, the structural complexity of nanocatalysts often obscures the identification of active sites and their role in catalytic performance, impeding rational catalyst design. Here, we develop a Cu/Cu ⁺ interface engineering strategy to elucidate active sites and their functions using model catalysts, enabling the rational design of efficient nanocatalysts for C–N coupling. Using Cu foil as a model system, we precisely modulate Cu/Cu ⁺ interfaces via femtosecond laser processing, confirming Cu/Cu ⁺ interfaces as the active sites and revealing the distinct roles of Cu and Cu ⁺ in CO ₂ and NO ₃ ⁻ reduction, respectively. Guided by these insights, we fabricate Cu nanowire catalysts with abundant Cu/Cu ⁺ interfaces through cyclic voltammetry activation. The optimized nanowire, with the highest interface density, achieves a urea Faradaic efficiency (FE) of 80% at 0 V versus the reversible hydrogen electrode (RHE). Furthermore, zirconia coating and electrochemical pulsing during reaction conditions enhance stability, maintaining a urea FE of ~ 70% over 80 hours. Mechanistic investigations demonstrate that adjacent Cu/Cu ⁺ sites synergistically reduce the energy barrier for the formation of the key *COOHNO ₂ intermediate, which arises from the coupling of *COOH and *NO ₂ , thereby facilitating efficient C–N bond formation. These findings bridge fundamental mechanistic understanding with practical catalytic performance.