Mg2FeH6 has been reported to reversibly store ca. 5.5 wt.%H2. Here we investigated hydrogen storage properties of Mg2FeH6-LiNH2 composite. Mg2FeH6 was destabilized by LiNH2, resulting in the release of 5.2 wt.%H2 below 300 °C. It was due to the metathesis reaction occurring while Mg2FeH6 and LiNH2 were ball-milled and heated at less than 200°C. Mg2FeH6 + 4LiNH2 → Li4FeH6 + 2Mg(NH2)2 ΔH = -92.8 kJ/mol Normally the syntheses of Li4FeH6 need at 5.5 GPa and 700°C by means of hydrogenation of LiH and Fe. Li4FeH6 and Mg(NH2)2 further dehydrogenated with a peak temperature of 226 °C, which was 76 °C lower than that of Mg2FeH6 self-decomposition. After the dehydrogenation, the composite re-absorbed only 3.8 wt.% H2 at 360 °C under the pressure of 30 bar H2 and became Mg(NH2)2, LiH and Fe.

Interaction between Mg2FeH6 and LiNH2 for hydrogen storage

255th National Meeting (2018)

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