Achieving Record-Breaking Urea Synthesis on Crystalline-Amorphous Hybrid via Electrochemical-Chemical Looping

Electrocatalytic C-N coupling of nitrate and CO₂ represents a paradigm shift in sustainable urea synthesis. We demonstrate that amorphous CuO_x-coated crystalline Cu nanowires achieve a record-breaking urea yield rate of 0.89 mol h^-1 g^-1 via novel electrochemical-chemical looping. Mechanistic investigations reveal a three-step catalytic cycle: (i) electro-reductive generation of Cu⁰ and oxygen vacancies (O_v); (ii) O_v-mediated nitrate activation via oxygen atom insertion, spontaneously yielding nitrogen-bonded nitrite (*NO₂) while oxidizing Cu⁰ to catalytically active Cu⁺; and (iii) Cu⁺-catalyzing C-N coupling between *NO₂ and CO₂ to form urea. This pathway circumvents conventional rate-limiting nitrate reduction step, reducing the electron transfer requirement from 16e^- to 12e^- for urea synthesis. Notably, direct nitrite utilization fails to generate Cu⁺ or nitrogen-bonded intermediates, instead forming oxygen-bonded species with markedly reduced C-N coupling activity-a finding that overturns conventional understanding. Our work establishes new fundamental principles for efficient urea synthesis and provides insights into catalyst design and green chemistry.