Highly efficient COx-free hydrogen evolution activity on rod Fe2N catalysts for ammonia decomposition

Abstract

Ammonia decomposition is a critical method for CO_x-free hydrogen production, and many metal nitrides have been studied as excellent catalysts for NH₃ decomposition recently. Here, Fe₂N catalysts with rod, cubical and discoidal structures were prepared via nitrogenization of the corresponding morphologies of Fe₂O₃ precursors, which were obtained by a hydrothermal synthesis method. These Fe₂N catalysts were characterized by XRD, TEM, BET, XPS and Mössbauer spectroscopy, and the results showed that the morphologies of Fe₂O₃ precursors had a significant effect on the crystallite size and yield of the nitride phase of Fe₂N catalysts. The rod Fe₂N had a small crystallite size and a high relative nitrogen content among the three samples. The catalytic activity for hydrogen production via ammonia decomposition was measured using a micro-fixed bed reactor under conditions of conventional pressure and a GHSV of 6000 mL g_cat⁻¹ h⁻¹. The rod Fe₂N exhibited a higher NH₃ conversion of 90% at 823 K compared with Fe₂N derived from cubical and discoidal Fe₂O₃, and maintained high stability for 40 h.