Hydrogen sorption properties of MgH2–NiCo2O4 composites activated mechanically under argon and hydrogen atmospheres

The effect of the mechanical activation medium on the hydrogen absorption–desorption properties of MgH2 with NiCo2O4 additives is investigated. The composite 90 wt.% MgH2–10 wt.% NiCo2O4 mechanically activated for 180 min under hydrogen reaches a higher absorption capacity as compared to the composite ground for the same time in an argon medium. At T = 573 K and P = 1 MPa the composite activated mechanically in a reactive medium shows a value of 5.67 wt.% while for the composite ground under argon the value is 4.36 wt.% only, both samples preserving a high absorption capacity at temperatures below 573 K. Addition of nickel cobaltite is found to have a favorable effect on the hydriding kinetics of magnesium. In order to elucidate this effect, a composite containing a large amount of NiCo2O4 (50 wt.%) is also investigated.