Catalytic effect of Ni nano-particle and Nb oxide on H-desorption properties in MgH2 prepared by ball milling

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 (similar to 6.5 wt.%) in the temperature range from 150 to 250 degrees C at heating rate of 5 degrees C/min. On the other hand, the MgH2 Composite with I mol% Nb-2 O-5 prepared by milling for a long time of 20 h at 400 rpm desorbed similar to 6.0 wt.% H-2 in the temperature range from 200 to 250 degrees C at heating rate of 5 degrees C/min. After second hydrogen absorption/desorption cycles at 200 degrees C, the HD properties of the Ni-catalyzed MgH2 composite became worse than those before cycling, while the Nb2O5-catalyzed composite showed better HD properties than those before cycling. (c) 2005 Elsevier B.V. All rights reserved.