Hydrogenation properties of nanocrystalline Mg- and Mg₂Ni-based compounds modified with platinum group metals (PGMs)

Nanocrystalline Mg-based compounds are attractive hydrogen storage materials. Further improved sorption kinetics can be combined with the intrinsically high storage capacity when using alloy additions or catalysts. In this work, platinum group metals (PGMs) have been employed to surface modify Mg- or Mg2Ni-based compounds. Nanocrystalline powders have been synthesised by high energy ball milling in hydrogen or argon atmospheres. The effects of co-milling time with the PGM, the use of pre-hydrided Mg for inert milling and blending with minor amounts of Ni are investigated. Gravimetric and thermal desorption studies combined with microstructural analysis using HRSEM and XRD demonstrate the usefulness of nanocrystallinity, thermodynamic destabilisation of the hydride and the catalytic properties of PGMs resulting in much reduced desorption temperatures. Reactively milled Mg2Ni co-milled for 1 h with Ru shows an onset temperature of hydrogen desorption as low as 80 degreesC. (C) 2002 Elsevier B.V. All rights reserved.