Magnesium-based nano-composite materials for hydrogen storage

Abstract

MgH 2 was mechanically milled with nano-Ni (nano-Ni/Al 2O 3/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 MgH 2 matrix. The nano-composite material with nano-Ni/Al 2O 3/C showed excellent properties as compared to that with Ni, a ball-milled MgH 2 and the mixture of MgH 2 and nano-Ni/Al 2O 3/C in terms of the H 2 desorption and absorption. The nano-composite material with nano-Ni/Al 2O 3/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.