Closing Electron Transfer Loop to Boost Electrocatalytic Urea Synthesis

The electrocatalytic C─N coupling of carbon dioxide and nitrate presents a promising approach for environmentally friendly urea synthesis. In this work, we propose a strategy to boost efficient and durable urea synthesis by coupling the electrochemical and chemical steps. Utilizing fullerene (C₆₀) as a redox-active electron mediator during the electrochemical reduction process, we effectively inhibit the irreversible reduction deactivation of positively charged copper (Cu^δ+) active sites. The electron-accepting fullerene form ions (C₆₀ ^n-) that engage in a spontaneous chemical redox reaction with nitrate ions, producing nitrite ions and regenerating neutral C₆₀ (C₆₀ ^n- + NO₃ ^- → C₆₀ + NO₂ ^-). This recycling mechanism closes the electron transfer loop while optimizing the overall reaction pathway. The urea yield rate is dramatically increased to 385.9 mmol h^-1 g^-1, accompanied by long-term durability. Our findings provide a valuable framework for designing highly efficient electrocatalyst for coupling reactions, advancing the field of sustainable urea synthesis.