Mechanistic Insights into the CO₂-Assisted NO Electrochemical Deoxygenation and Hydrogenation

Electrocatalytic NO reduction to NH₃ holds significant potential for pollutant treatment and resource recovery. Herein, we report that the introduction of CO₂ on octahedral oxide-derived copper (o-OD-Cu) significantly enhances the electrochemical reduction of NO to NH₃. With 10% NO in a CO₂ environment, the Faradaic efficiency for NH₃ production in a flow cell remains around 80% over a wide current density range from 20 to 250 mA cm^-2. At a current density of 250 mA cm^-2, the yield can reach up to 1403.9 µmol cm^-2 h^-1, which is 3.71 times higher than without CO₂ and surpasses the performance reported in similar literature. Moreover, even at a low concentration of 1% NO, the Faradaic efficiency can reach a maximum of 70.11% at a current density of 20 mA cm^-2. In situ investigations and theoretical calculations revealed that, in the coexistence of NO and CO₂, the NO reduction pathway involves a unique route wherein *CO and *COOH, produced from CO₂ reduction, can respectively promote the deoxygenation of *NO and hydrogenation of *N by acquiring O atoms from *NO and providing H atoms for the sustained hydrogenation of *N, thereby accelerating the conversion process of NO to NH₃.