Combined catalyst–pathway design for efficient and green urea synthesis

Abstract

Urea electrosynthesis from CO₂ + NO₃⁻ co-electrolysis (UECN) offers a promising pathway for sustainable urea synthesis, while necessitating rational catalyst/pathway design to boost CO₂/NO₃⁻ co-activation and C–N coupling. Herein, we demonstrate an atomically dispersed Ag on oxygen vacancy (OV)-rich TiO₂ (Ag₁/TiO_2−x) catalyst for efficient UECN. Theoretical calculations and in situ spectroscopic analyses reveal the synergy of OV-induced Ag_1-OV and Ti_OV dual-sites in promoting the selective C–N coupling of *CO and *NO₂ for target urea generation. Notably, with the integration of plasma-assisted air-to-NO_x⁻ conversion and CO₂ + NO_x⁻ co-electrolysis, Ag₁/TiO_2−x achieves an exceptional urea faradaic efficiency of 75.7% and a urea yield rate of 74.6 mmol h⁻¹ g⁻¹ along with excellent catalytic stability.