Fe-based catalyst derived from MgFe-LDH: Very efficient yet simply obtainable for hydrogen production via ammonia decomposition

The current study provided the first example to develop the Fe-based catalyst for CO_x-free hydrogen production via ammonia decomposition through the unique MgFe-layered double hydroxides (MgFe-LDHs) of different stoichiometric Mg/Fe ratio. The so obtained Fe-based catalyst is low-cost, readily obtainable, and environmentally friendly. Structurally, the Fe(FeN_x) species are 3D-isolated by the nano-MgO entities, improving anti-sintering potential of Fe(FeN_x); and electronically, the Fe (FeN_x) species are promoted by the nano-MgO matrix, showing the strongest promoting effect of MgO on Fe(FeN_x). At a GHSV_NH3 of 150,000 mL g_cat⁻¹ h⁻¹, the current N–Mg_5.3FeO_m catalyst can give an outstanding H₂ formation rate of 9.83 mol g_cat⁻¹ h⁻¹ at 680 °C and a TOF_H2 = 2.19 s⁻¹ at 530 °C. The influence of Mg/Fe constitution on catalyst structure, surface property, and performance was systematically investigated. The in-situ ammonia treatment was superior to the usually adopted hydrogen pre-reduction for the Fe–Mg oxide precursor, leading to easy development of small sized FeN_x specimen and activity enhancement.