Hydrogen storage is one of the key enabling technologies for realization of future hydrogen society. Mg-based materials have been extensively studied as candidates for hydrogen storage due to the advantages such as low cost, great abundance of Mg and large hydrogen storage capacity (7.7 wt% for MgH2). However, poor kinetics and great enthalpy change of the desorption reaction greatly hindered the possible storage application. Mg-based hydrogen storage materials usually need a temperature above 500 K to absorb hydrogen.Mg-Co alloys with BCC structure were found to be able to absorb hydrogen with a capacity around 3 wt% at 258 K-the lowest temperature reported so far for Mg-based materials to absorb hydrogen. The particle size is 1-3 micrometers and the grain size is a few nanometers. Large surface area, short diffusion distance of nanostructure, numerous defects introduced from the milling process and BCC lattice structure are important factors for the kinetics enhancement compared to micrometer scale samples. The highest H/M ratios found so far for BCC metal lattice hydrides are 1.28 for Mg55Co45H128 and 1.33 for Mg2CaV3H8. This can be explained from geometrical effect aspect of the BCC metal lattice interstitial hydrides with a lattice parameter about 0.30 nm.

Geometrical effect study in Mg-based BCC structure nanomaterials

246th National Meeting (2013)

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