Boosting the Urea Synthesis Rate on Ni Single-Atom Catalysts: The Impact of Acetonitrile Electrolyte in the Tandem CO2 Reduction/Nucleophilic Addition Reaction

The tandem CO2 reduction reaction (CO2RR) process/nucleophilic addition reaction can be an efficient and environmentally friendly method for the synthesis of urea. However, the low stability of the CO2•– intermediates causes a low yield of urea through the nucleophilic addition reaction. Here, we propose an effective method to improve the yield of nucleophilic addition to synthesize urea on Ni single-atom catalysts (Ni-SACs) by introducing acetonitrile into aqueous electrolytes. A high yield of urea of 1.10 mM·g–1·h–1 was achieved on the Ni-SACs at −2.2 V (vs saturated calomel electrode) in acetonitrile/water mixture electrolytes, presenting the best performance for urea synthesis via the nucleophilic addition reaction reported so far. Further studies have shown that the acetonitrile stabilizes the CO2•– intermediates on the one hand and on the other hand, it lowers the energy barrier of the nucleophilic addition reaction on Ni-SACs through coordination, thus increasing an overall kinetic rate for urea formation.