Kinetic Enhancement of Direct Hydrogenation of MgB2 to Mg(BH4)2 upon Mechanical Milling with THF, MgH2, and/or Mg

Modification of magnesium diboride, MgB2, by mechanical milling with THF, MgH2, and/or Mg results in a lowering of the conditions required for its direct, bulk hydrogenation to magnesium borohydride, Mg(BH4)(2), by 300bar and 100 degrees C. Following mechanical milling with MgH2 or THF and Mg, MgB2 can be hydrogenated to Mg(BH4)(2) at 300 degrees C under 700bar of H-2 while achieving approximate to 54-71% conversion to the borohydride. The discovery of a means of dramatically lowering the conditions required for the hydrogenation of MgB2 is an important step towards the development of a practical onboard hydrogen storage system based on hydrogen cycling between Mg(BH4)(2) and MgB2. We suggest that mechano-milling with THF, Mg, and/or MgH2 may possibly introduce defects in the MgB2 structure which enhance hydrogenation. The ability to activate the MgB2 through the introduction of structural defects transcends its relevance to hydrogen storage, as a method of overcoming its chemical inertness provides the key to harnessing other interesting properties of this material.