Polymetallic Oxide Catalysts for Electrocatalytic Synthesis of Urea from N₂ and CO₂ at Ultralow Applied Voltage

Due to operation at ambient temperature and pressure, the electrocatalytic synthesis of urea from N2 and CO2 is promising. However, the high consumption of electrical energy reduces the interest of the industrial sector. Reducing the applied voltage for the electrocatalytic synthesis of urea is an urgent issue to be solved. Herein the polymetallic oxide FeCoNiCuMOx (M = Ce, Mg, In, Zn) catalysts have been fabricated, and their catalytic performance for electrocatalytic urea synthesis has been investigated. Among those catalysts, the FeCoNiCuCeOx catalyst shows the highest activity and selectivity toward urea. At an ultralow applied voltage of −0.2 V (vs RHE), the formation rate of urea reaches 6.37 mmol gcat–1 h–1, with a corresponding Faradaic efficiency of 26.7%. The oxygen vacancy in FeCoNiCuCeOx plays a crucial role in enhancing the catalytic performance by facilitating the adsorption/activation of CO2 and N2. The higher adsorption capacity and binding energy of CO2 and N2 lead to a higher electrocatalytic performance of FeCoNiCuCeOx. Higher C–N coupling efficiency originates from higher coverage of *CO and optimal binding strength between *CO and the catalyst surface. The synergy of CuFe2O4/CoNiO2 and CeO2 with an oxygen vacancy enhances the electrocatalytic performance of FeCoNiCuCeOx.