Metal oxides as catalysts for improved hydrogen sorption in nanocrystalline Mg-based materials

Nanocrystalline MgH2/MexOy - and Mg2NiH4/MexOy-powders were produced by hig h energy ball milling (MexOy=Sc2O3, TiO2, V2O5, Cr2O3, Mn2O3, Fe3O4, CuO, A l2O3, SiO2). The hydrogen absorption and desorption kinetics of the nanocom posite materials were determined with respect tu a technical application. S ome of the selected oxides lead to an enormous catalytic acceleration of hy drogen sorption compared to pure nanocrystalline materials. In absorption. the catalytic effect of TiO2,V2O5, Cr2O3, Mn2O3, Fe3O4, and CuO is comparab le. Concerning desorption, the composite material containing Fe3O4 shows th e fastest kinetics followed by V2O5, Mn2O3, Cr2O3 and TiO2. Only 0.2 mole% of the catalysts is sufficient to provide a fast sorption kinetics. (C) 200 1 Elsevier Science B.V. All rights reserved.