Cyclic hydrogen storage properties of Mg milled with nickel nano-powders and MnO2

The cyclic hydrogen storage properties of nanocrystalline composite of Mg–3Ni–2MnO2 (wt.%) produced by mechanical milling with nickel nano-powders under hydrogen pressure and its structural changes have been investigated. The results show that the composite has excellent hydrogen storage properties. Its maximum hydrogen capacity is about 6.5 wt.%. The hydrogen absorption time is ∼50 s in which 6.37 wt.% of hydrogen has been absorbed at 200 °C. The hydrogen desorption time is ∼310 s in which the same amount of hydrogen has been discharged in the temperature range from 285 to 310 °C under hydrogen pressure of 0.1 MPa. The composite also has a better cyclic hydrogen storage property. After 60 times of cycling, the hydrogen capacity decreases less than 0.1 wt.%. However, the hydrogen absorption time and desorption time are increased with the cyclic numbers. The reasons for these may be that the MgO, formed during the cycling process, impedes contact of the catalyst with the MgH2.