Dynamic Reconstitution Between Copper Single Atoms and Clusters for Electrocatalytic Urea Synthesis

Electrocatalytic C-N coupling between carbon dioxide and nitrate has emerged to meet the comprehensive demands of carbon footprint closing, valorization of waste, and sustainable manufacture of urea. However, the identification of catalytic active sites and the design of efficient electrocatalysts remain a challenge. Herein, the synthesis of urea catalyzed by copper single atoms decorated on a CeO2 support (denoted as Cu-1-CeO2) is reported. The catalyst exhibits an average urea yield rate of 52.84 mmol h(-1) g(cat.)(-1) at -1.6 V versus reversible hydrogen electrode. Operando X-ray absorption spectra demonstrate the reconstitution of copper single atoms (Cu-1) to clusters (Cu-4) during electrolysis. These electrochemically reconstituted Cu-4 clusters are real active sites for electrocatalytic urea synthesis. Favorable C-N coupling reactions and urea formation on Cu-4 are validated using operando synchrotron-radiation Fourier transform infrared spectroscopy and theoretical calculations. Dynamic and reversible transformations of clusters to single-atom configurations occur when the applied potential is switched to an open-circuit potential, endowing the catalyst with superior structural and electrochemical stabilities.