Mechanochemistry and H-sorption properties of Mg2FeH6-based nanocomposites

Mg2FeH6 is a promising material for hydrogen storage applications, since it presents the highest known volumetric capacity of 150 kg m(-3) of H-2 and its metallic constituents are inexpensive. The major drawbacks for its application are the difficulties associated with its synthesis and also its high thermal stability. In this paper. Mg2FeH6-based nanocomposites were prepared from the elements via reactive milling. A high-yield of the complex hydride synthesis was obtained after a systematic processing study, and the best conditions were successfully extended to the mechanochemical synthesis of Mg2CoH5. The influence of different additives such as transition metals, transition metal fluorides and graphite on the H-sorption behavior of the Mg2FeH6-based nanocomposites was evaluated. Mixtures rich in both MgH2 and Mg2FeH6 hydrides present lower temperature ranges of hydrogen release than those which are rich in only one of these hydrides. The MgH2-Mg2FeH6-based nanocomposite presents ultra-fast H-sorption kinetics at 300 degrees C with partial reversible formation of Mg2FeH6.