Deuterium Isotope Analysis of Electrochemical Promotion in Ammonia Synthesis on Iron-Based Catalyst

Abstract

In this study, the deuterium isotope analysis was conducted to investigate the electrochemical promotion mechanism of ammonia synthesis at 650˚C using H2-N2, 1%W-10%Fe-BaCe0.9Y0.1O3 (BCY)|BCY|Pt, 3%H2O-10%D2-87%Ar. The performance of ammonia electrochemical synthesis was examined using high pressure liquid chromatography (HPLC) and Fourier-transform infrared spectroscopy (FTIR). The ammonia formation rate increased by around 20 times with an increase in cathodic polarization. The electrochemical synthesized ammonia of NH3 and NH2D were detected by FTIR. Furthermore, a positive correlation between the ammonia formation rate and hydrogen partial pressure in the cathode was observed. Considering the results, the electrochemical promotion mechanism of ammonia formation was probably caused by accelerated N2 dissociation via supplying D+, subsequently N* and ND* were formed from N2D*, and then ND* and N* reacted with H* which originated from H2 fed in the cathode to form NH2D and NH3.

Iron-Based Electrode Structures for Ammonia Electrosynthesis Cells with Proton-Conducting Ceramic Electrolytes

“…However, much of the mechanism remains unclear, especially in the specific scope of ammonia synthesis. Based on results from an isotopic analysis, our group proposed that protons conducted via the electrolyte aid N2 dissociation, but that the subsequent nitrogen hydrogenation steps occur using gaseous H2 fed into the cathode side (7)(8).…”