Effect of synthesis route on the hydrogen storage properties of 2MgH2–Fe compound doped with LiBH4

• Hydrogen storage properties of MgH2 and Fe doped with LiBH4 were investigated.
• Hydrogenation reversibility was enhanced with the LiBH4.
• Formation of MgH2 precludes the formation of Mg2FeH6.

The hydrogen storage properties of a 2:1 mol ratio of MgH2 and Fe with or without 10 wt.% of LiBH4 were investigated. Two doping methods were used: the first one consisted of two steps: first the 2MgH2 + Fe mixture was ball milled for 10 h and subsequently LiBH4 was added and milling resumed for 1 more hour. In the second method all materials were mixed and ball milled for 10 h. The first method produced materials with an hydrogen dehydrogenation capacity of 2.69 wt.% at 623 K and that could re-absorb 2.93 wt.% H2. The materials made by the second method presented a hydrogen dehydrogenation capacity of 2.98 wt.% at 623 K and re-absorbed 3.10 wt.% H2. For both methods, the rehydrided sample consisted only of MgH2. The reversibility of the reaction was enhanced with the LiBH4, but this additive, by acting as a catalyst for the formation of MgH2, precludes the formation of Mg2FeH6.