Selective electrosynthesis of urea from nitrate and carbon dioxide with low overpotential.

Abstract

Reducing the energy cost and CO₂ emission of traditional urea synthesis through alternative strategy is crucial for the sustainable social development. Herein, we report the electrosynthesis of urea from nitrate and CO₂ on Ag/CdO heterostructured catalyst with low overpotential. The optimized Ag_0.07/CdO catalyst demonstrates a high urea yield rate of 111.6 ± 3.1 mmol g_cat.^-1 h^-1 with 50.0 ± 2.7% Faradaic efficiency at -0.15 V vs. RHE in a flow cell, and can further achieve a urea yield rate of 427.0 ± 30.2 mmol g_cat.^-1 h^-1 in an optimized two-electrode cell with stable response for 1000 h. Operando spectroscopy and theoretical calculations indicate that Ag attracts *NO₂ intermediate as well as promotes the reconstruction of CdO into low coordinated CdCO₃ that facilitate the activation of CO₂, thus benefits *CO/*NO₂ adsorption and coupling at low overpotential as well as suppresses the generation of CO and NH₃ by-products.