High hydrogen storage capacity of nanosized magnesium synthesized by high energy ball-milling

To prepare nanosized magnesium which reversibly absorbs hydrogen with high capacity even under mild conditions, high energy ball-milling of Mg or MgH2 with benzene or cyclohexane as additives have been studied. In ball-milling of Mg or MgH2, the use of the organic additives is very crucial in determining the characteristics of the resulting nanosized magnesium. Benzene and cyclohexane served to maintain the high-degree dispersion of nanostructured magnesium with small crystallite sizes (9-10 nm) and high surface areas (24-25 m2 g−1). The behavior of hydrogen absorption by the magnesium was extensively evaluated by differential scanning calorimetry (DSC) measurements and volumetric techniques. The nanosized magnesium prepared by ball-milling of MgH2 with benzene showed reversible DSC traces for hydriding/dehydriding under 0.1 MPa hydrogen pressure. Moreover, 1 at.% Al-doped or 2.9 at.% Ni-doped nanosized samples obtained by milling of MgH2 with solutions of Al(C2H5)3 or Ni(C5H5)2 in benzene showed satisfying hydrogen absorption rates, respectively. The reversible hydrogen absorption by the 1 at.% Al-doped sample approximately reached a maximal capacity of 7.3 wt.% even at a 0.1 MPa H2 atmosphere.