Co-reduction Coupling of Bicarbonate and Nitrate toward Efficient Urea Synthesis

Abstract

The electrocatalytic reduction of carbon dioxide (CO₂) and different nitrogenous substances has shown a broad prospect in replacing the traditional urea synthesis process, but there are still serious challenges in mass transfer at the gas-liquid-solid interface. Unlike conventional CO₂ as a carbon source, the conversion of HCO^3- and NO^3- to urea by C-N coupling process under environmental conditions is a promising alternative to traditional industrial urea synthesis. However, initiating the C-N coupling reaction through the adsorption and activation of HCO^3- and NO^3- is considerably challenging. Designing and engineering highly selective and active electrocatalysts is necessary to accelerate electrochemical urea synthesis. Herein, we construct a Mott-Schottky heterogeneous catalyst by loading Cu nanoparticles onto WN nanosheets (Cu-WN), achieving the excellent Faradic efficiency (FE) of 15.9% and urea yield rate of 421 µg h^-1 mgcat^-1 at -0.3V (vs. RHE), outperforming the majority of reported electrocatalysts. The results show the spatial charge region induced by Mott-Schottky heterostructure facilitates the simultaneous adsorption and activation of HCO^3- and NO^3-, accelerating the multiple-electron transfer process. This work furnishes a promising impetus for the advancement of urea electrosynthesis via electrochemical C-N coupling under ambient conditions.