Activity-Selectivity Trends in Electrochemical Urea Synthesis: Co-Reduction of CO₂ and Nitrates Over Single-Site Catalysts

Electrochemical co-reduction of carbon dioxide and nitrates (CO₂NO₃RR) holds promise for sustainable urea production. However, the sluggish kinetics of the sixteen-electron transfer and unclear mechanistic understanding strongly impede its development. Here, combined experimental and computational approaches are employed to screen a series of metal phthalocyanine as model catalysts (MPcs, M = Zn, Co, Ni, Cu, and Fe) to uncover the activity-selectivity trends in electrochemical CO2NO₃RR. The theoretical simulations reveal that the thermodynamics of urea synthesis is significantly influenced by key intermediates, where the enhanced adsorption of *HOOCNO, coupled with reduced adsorptions of *N and *COOH, and moderate adsorption of *H₂O, can significantly promote the urea production. 𝚫G_*HOOCNO−𝚫G_*N−𝚫G_*COOH+𝚫G_*H2O as a potential descriptor is proposed for predicting the efficiency of CO₂NO₃RR toward urea formation. The findings provide systematic guidance for the future design of high-efficiency catalysts for urea electrosynthesis, addressing a crucial need for sustainable nitrogen fixation.