We examined the catalytic effect of Ni nano-particle and Nb oxide on hydrogen desorption (HD) properties in MgH2 prepared by mechanical ball milling under a hydrogen gas atmosphere of 1 MPa. The MgH2 composite with 2 mol% Ni nano-particle prepared by milling for a short time of 15 min at 200 rpm desorbed a large amount of hydrogen (∼ 6.5 wt.%) in the temperature range from 150 to 250 ° C at heating rate of 5 ° C/min. On the other hand, the MgH2 composite with 1 mol% Nb2O 5 prepared by milling for a long time of 20 h at 400 rpm desorbed ∼ 6.0 wt.% H2 in the temperature range from 200 to 250 ° C at heating rate of 5 ° C/min. After second hydrogen absorption/desorption cycles at 200 ° C, the HD properties of the Ni-catalyzed MgH2 composite became worse than those before cycling, while the Nb2O 5-catalyzed composite showed better HD properties than those before cycling.
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