A New Method for Urea Synthesis under Environmental Conditions Based on Nucleophilic Addition Reaction During Electrochemical CO2 Reduction

Abstract

AbstractUrea (H2NCONH2) is a commercially indispensable chemical as a fertilizer and starting material for the manufacture of many other products. Currently, commercial urea can be prepared with an energy‐consuming process by combining liquid ammonia (NH3) and liquid carbon dioxide (CO2) under high‐temperature and high‐pressure conditions. An alternative approach for synthesis of urea may involve electrochemical synthesis reactions that occur under aqueous and ambient conditions. Here, we propose synthesis of urea via nucleophilic addition reaction during an electrochemical CO2 reduction process in NH4HCO3‐containing electrolytes. The urea formation at a rate of 0.11 mmol g−1 h−1 was achieved on a polycrystalline Au electrode (area: 1 cm2) at a potential of −1.4 V (vs. saturated calomel electrode). Furthermore, the detailed investigations including in‐situ spectroscopic analysis and isotopic labeling characterization reveal the capability of producing urea could be mainly attributed to a spontaneous reaction between the NH3 molecule and the CO2⋅− intermediate. This study promotes the exploration of electrochemical synthesis of high‐value‐added products.