Magnesium-based nano-composite materials for hydrogen storage

MgH2 was mechanically milled with nano-Ni (nano-Ni/Al2O3/C) and Ni catalysts (Ni), yielding Mg-based nano-composite materials. X-ray and TEM measurements revealed that nano-Ni particles, which are 6-20 nm size, were dispersed in the MgH2 matrix. The nano-composite material with nano-Ni/Al2O3/C showed excellent properties as compared to that with Ni, a ball-milled MgH2 and the mixture of MgH2 and nano-Ni/Al2O3/C in terms of the H-2 desorption and absorption. The nano-composite material with nano-Ni/Al2O3/C desorbed H-2 of 4.9-5.8 wt.% at 423-473 K, while the mixture could not desorb H-2 at the temperature. The H-2 absorption capacity at 9 MPa and room temperature in 6 h. increased from below 0.1 wt.% for the mixture to 5.0 wt.% for the nano-composite material, approaching a maximum of 6.5 wt.% in 70 h. The catalyst activity was improved with decreasing Ni size. The improved kinetics is indicated by the small activation barrier, the large collision frequency, the short diffusion path length and the high driving force. (c) 2005 Elsevier B.V. All rights reserved.