Elucidation of the electrocatalytic activity origin of Fe3C species and application in the NOx full conversion to valuable ammonia

Conversion of nitrogen oxides (NOx) into ammonia mediated by electrochemical nitrate/nitrite reduction is an ideal route for the treatment and utilization of NOx pollutants. Herein, pure-phase Fe3C nanoparticle supported on N-doped carbon nanotubes catalysts exhibit an NH3 yield rate of 1034.9 μmol h−1 cm−2 with a Faradaic efficiency of 97.3% for NO3− reduction reaction. The excellent intrinsic activity of Fe3C species is attributed to a superior ability to adsorb and activate NO3− and a proper ability to activate protons. The electrochemical in situ FTIR spectra, in situ Raman spectra and density functional theory calculations reveal the reaction process follows a novel multiple reaction pathway. Eventually, a demonstration device is proposed for a full conversion process from NOx to ammonia synthesis including NOx collection, electrochemical nitrate/nitrite reduction and ammonia collection, which made it possible to integrate the green ammonia synthesis system with distributed nitrogen oxide discharge sites.