Hydrogen sorption kinetics of magnesium hydride enhanced by the addition of Zr8Ni21 alloy

Hydrogen absorption and desorption kinetics, and thermodynamics of MgH2 ball milled with addition of the Zr8Ni21 alloy have been studied. Different additive amounts were used from 3 to 12.5 wt%. The highest reversible capacity of 6.5 wt% of hydrogen was found for the samples with 3 and 5 wt% of additive. The best reaction kinetics was found with 10 wt% of additive: 5.9 wt% H2 was desorbed in 4 min at 300 °C and 0.1 bar of hydrogen pressure. Regardless of the different storage capacities, all the samples were almost fully hydrided in 1 min using a hydrogen pressure of 10 bar at 250 and 300 °C. The enthalpy of formation of magnesium hydride was not affected by the presence of the additive.

► Improvement of hydrogen absorption and desorption kinetics of MgH2 by Zr8Ni21 addition.
► A desorption rate of 3.8 wt%/s is obtained, similar to the best results found in literature.
► A reversible capacity of 6.5 wt% at 300 °C is obtained with 5 wt% additive amount.