Structure, morphology and hydrogen storage kinetics of nanocomposite MgH₂/10 wt% ZrNi₅ powders

Reactive ball milling was employed to synthesize nanocrystalline MgH₂ powders under a hydrogen gas pressure of 50 bar for 200 h, using a high-energy ball milling. In part to improve the hydrogen absorption/desorption kinetics of as-prepared MgH₂, the powders were doped with 10 wt% ZrNi₅ powders and then mechanically ball milled for 50 h. The nanocomposite powders possessed superior hydrogenation/dehydrogenation properties, indexed the short time required for achieving a complete hydrogen absorption (1 min) and desorption (10–12 min) of 5.3 wt% H₂ at 275 °C. van't Hoff approach was used to calculate the enthalpy of hydrogenation and dehydrogenation for MgH₂ phase in the nanocomposite powders and found to be −72.85 and 77.07 kJ/mol, respectively. Moreover, this nanocomposite system possessed excellent hydrogen absorption/desorption cyclability of 600 complete cycles, conducted at 275 °C with a cyclic-life-time reached to 568 h without serious kinetics degradation.