Hydrogen storage in magnesium based alloys

Density functional theory calculations of various magnesium alloys and their hydrides were carried out to find candidates for efficient hydrogen storage for mobile applications. Magnesium hydride has two major problems, i.e., the binding energy of hydrogen is too large, leading to a release temperature of 700 K while 400 K is preferable; and the rate of diffusion of hydrogen through the hydride is extremely slow making loading and unloading of hydrogen impractical. Ways were searched to modify the properties of magnesium hydride by small additions of other elements to reduce these two problems while still keeping the advantages of magnesium hydride. Addition of 10-15% of other light metals lowered the binding energy down to target values. Furthermore, the addition of a similar amount of transition metal elements greatly increased the diffusivity through a long range electron transfer mechanism. The problem was finding stable alloys that can be reversibly loaded and unloaded without decomposing. This is an abstract of a paper presented at the 229th ACS National Meeting (San Diego, CA 3/13-17/2005).