Urea Synthesis via Coelectrolysis of CO₂ and Nitrate over Heterostructured Cu-Bi Catalysts

Electrocatalytic coupling of CO₂ and NO₃^- to urea is a promising way to mitigate greenhouse gas emissions, reduce waste from industrial processes, and store renewable energy. However, the poor selectivity and activity limit its application due to the multistep process involving diverse reactants and reactions. Herein, we report the first work to design heterostructured Cu-Bi bimetallic catalysts for urea electrosynthesis. A high urea Faradaic efficiency (FE) of 23.5% with a production rate of 2180.3 μg h^-1 mg_cat^-1 was achieved in H-cells, which surpassed most reported electrocatalysts in the literature. Moreover, the catalyst had a remarkable recycling stability. Experiments and density functional theory calculations demonstrated that introduction of moderate Bi induced the formation of the Bi-Cu/O-Bi/Cu₂O heterostructure with abundant phase boundaries, which are beneficial for NO₃^-, CO₂, and H₂O activation and enhance C-N coupling and promote *HONCON intermediate formation. Moreover, favorable *HNCONH₂ protonation and urea desorption processes were also validated, further explaining the reason for high activity and selectivity toward urea.