Boosting Urea Electrosynthesis via Asymmetric Oxygen Vacancies in Zn-Doped Fe2O3 Catalysts.

Urea electrosynthesis from CO2 and nitrate (NO3 -) provides an attractive pathway for storing renewable electricity and substituting traditional energy-intensive urea synthesis technology. However, the kinetics mismatching between CO2 reduction and NO3 - reduction, as well as the difficulty of C─N coupling, are major challenges in urea electrosynthesis. Herein, we first calculated the free energy of *CO, *OCNO, and *NOH formation over defect-rich Fe2O3 catalysts with different metal dopants, which showed that Zn dopant was a promising candidate. Based on the theoretical study, we developed Zn-doped defect-rich Fe2O3 catalysts (Zn-Fe2O3/OV) containing asymmetric Zn-OV-Fe sites. It exhibited an outstanding urea faradaic efficiency of 62.4% and the remarkable recycling stability. The production rate of urea was as high as 7.48 mg h-1 mgcat -1, which is higher than most of the reported works to date. Detailed control experiments and in situ spectroscopy analyses identified *OCNO as a crucial intermediate for C─N coupling. The Zn-Fe2O3/OV catalyst with asymmetric Zn-OV-Fe sites showed enhanced *CO coverage and promoted *OCNO formation, leading to high efficiency toward urea production.