The hydrogenation properties of magnesium hydride mechanically milled with iron fluorides (FeF
2 and FeF
3), were investigated by Temperature Programmed Desorption (TPD) and volumetric methods using a Sieverts-type apparatus, as
prepared upon dehydrogenation and finally upon subsequent hydrogenation. The activation energy of hydrogen desorption (E
a), calculated from the Kissinger formula using TPD measurements obtained with different heating rates, showed significant
decreases of Ea in comparison to that of milled MgH
2 without any dopants. Moreover, the influence of these metal fluorides on the thermodynamics of the decomposition process
was also examined. In the case of the FeF
2 dopant, rehydrogenation following desorption caused the complete decomposition of the iron fluoride to BCC iron and the formation
of a predominant MgH
2 phase. In contrast to FeF
2, the addition of FeF
3 led to the formation of β-MgH
2 as a major phase coexisting with Mg
2FeH
6 and MgF
2 compounds. The presence of pure Fe in the MgH
2+FeF
2 composite, as opposed to MgH
2+FeF
3 containing Mg
2FeH
6 and MgF
2, did not cause any significant influence on the sorption properties of MgH
2. Moreover, the original material doped with FeF
3 predominantly showed iron in the Mg
2FeH
6 compound, while the FeF
2 dopant iron mostly showed the nearly pure BCC metallic phase
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