Photoelectrocatalytic Synthesis of Urea from Carbon Dioxide and Nitrate over a Cu₂O Photocathode

Transformation of carbon dioxide and nitrate ions into urea offers an attractive route for both nitrogen fertilizer production and environmental remediation. However, achieving this transformation under mild conditions remains challenging. Herein, we report an efficient photoelectrochemical method for urea synthesis by co-reduction of carbon dioxide and nitrate ion over a Cu₂O photocathode, delivering urea formation rate of 29.71±2.20 μmol g^-1 h^-1 and Faradaic efficiency (FE) of 12.90±1.15 % at low external potential (-0.017 V vs. reversible hydrogen electrode). Experimental data combined with theoretical calculations suggest that the adsorbed CO* and NO₂* species are the key intermediates, and associated C-N coupling is the rate-determining step. This work demonstrates that Cu₂O is an efficient catalyst to drive co-reduction of CO₂ and NO₃ ^- to urea under light irradiation with low external potential, showing great opportunity of photoelectrocatalysis as a sustainable tool for value-added chemical synthesis.