Hydrogen-storage property characterization of Mg–15 wt%Ni–5 wt%Fe2O3 prepared by reactive mechanical grinding

Mg–15 wt%Ni–5 wt%Fe2O3 (Mg155) was prepared by reactive mechanical grinding (RMG). Mg155 exhibited high hydriding and dehydriding rates even at the first cycle, and its activation was completed after only two hydriding–dehydriding cycles. The activated Mg155 absorbed 5.06 and 5.38 wt% of hydrogen, respectively, for 5 and 60 min at 573 K under 12 bar H2. It desorbed 1.50 and 5.28 wt% of hydrogen, respectively, for 5 and 60 min at 573 K under 1.0 bar H2. The initial hydrogen absorption rate decreased, but the hydrogen desorption rate increased rapidly with an increase in temperature from 563 K to 603 K. The rate-controlling step for the dehydriding reaction in a range from F ≃ 0.20 to F ≃ 0.75 is considered to be the chemical reaction at the Mg hydride/α-solid solution interface. The absorption and desorption PCT curves exhibited two plateaus at 573 K. The hydrogen-storage capacity of the activated Mg155 was about 6.43 wt% at 573 K.