Phase-Controlled Copper Catalysts Derived from ZIFs for Electrochemical Urea Synthesis via CO₂ and Nitrate Reduction

Electrochemical urea synthesis from CO₂ and nitrate is a promising route for sustainable fertilizer production, yet the role of different catalyst phases remains unclear. Here, we report a phase-controlled copper catalyst system derived from Cu-doped ZIF-8, enabling a transition from atomically dispersed Cu─N sites to metallic Cu nanoparticles within N-doped carbon frameworks. Among them, the Cu─N coordinated catalyst exhibits superior performance, delivering the lowest onset potential and highest selectivity in H-cell measurements. In a flow cell, it optimized a faradaic efficiency of 49% and a urea yield rate of 2,970 mg g^-1 h^-1 at -0.5 V vs RHE. Mechanistic studies reveal that Cu single-atom sites facilitate C─N coupling and lower the energy barrier for urea desorption. Electronic structure analysis indicates optimized intermediate binding, suppressing competing reactions. These findings highlight the importance of phase-controlled Cu catalysts for efficient urea electrosynthesis.