Mg2FeH6–LiBH4 and Mg2FeH6–LiNH2 composite materials for hydrogen storage

Two composite hydrogen storage materials based on Mg2FeH6 were investigated for the first time. The Mg2FeH6–LiBH4 composite of molar ratio 1:5 showed a hydrogen desorption capacity of 5.6 wt.% at 370 °C, and could be rehydrogenated to 3.6 wt.% with the formation of MgH2, as the material was heated to 445 °C and held at this temperature. The Mg2FeH6–LiNH2 composite of 3:10 molar ratio exhibited a hydrogen desorption capacity of 4.3 wt.% and released hydrogen at 100 °C lower then the Mg2FeH6–LiBH4 composite, but this mixture could not be rehydrogenated. Compared to neat Mg2FeH6, both composites show enhanced hydrogen storage properties in terms of desorption kinetics and capacity at these low temperatures. In particular, Mg2FeH6–LiNH2 exhibits a much lower desorption temperature than neat Mg2FeH6, but only Mg2FeH6–LiBH4 re-absorbs hydrogen.

► First destabilization study of Mg2FeH6 for hydrogen storage.
► LiNH2- and LiBH4-destabilized Mg2FeH6 showed improved H2 desorption.
► LiBH4–Mg2FeH6 is partially reversible.