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.