Amorphous MnO2 with low-coordinated Mn sites for efficient electrochemical urea production from CO2 and NO

Abstract

Electrochemical urea synthesis from CO₂ and NO co-electrolysis (EUCN) offers a promising approach for simultaneously converting harmful NO/CO₂ emissions into value-added urea under ambient conditions. Herein, amorphous MnO₂ (a-MnO₂) with rich oxygen vacancies (OVs) is explored as a high-performance catalyst for EUCN, showing the exceptional faradaic efficiency of 36.69% and urea yield rate of 51.96 mmol h⁻¹ g⁻¹ in a membrane electrode assembly electrolyzer. Combined experimental and theoretical analyses reveal that the enhanced EUCN performance of a-MnO₂ originates from the critical role of low-coordinated Mn sites adjacent to OV (L-Mn_OV) in promoting NO activation and lowering the energy barrier for C–N coupling while inhibiting the competing side reactions, consequently leading to efficient and selective urea generation.