Hydrogen storage properties of nanostructured MgH2/TiH2 composite prepared by ball milling under high hydrogen pressure

Nanostructured MgH2/0.1TiH(2) composite was synthesized directly from Mg and Ti metal by ball milling under an initial hydrogen pressure of 30 MPa. The synthesized composite shows interesting hydrogen storage properties. The desorption temperature is more than 100 degrees C lower compared to commercial MgH2 from TG-DSC measurements. After desorption, the composite sample absorbs hydrogen at 100 degrees C to a capacity of 4 mass% in 4 h and may even absorb hydrogen at 40 degrees C. The improved properties are due to the catalyst and nanostructure introduced during high pressure ball milling. From the PCI results at 269, 280, 289 and 301 degrees C, the enthalpy change and entropy change during the desorption can be determined according to the van't Hoff equation. The values for the MgH2/0.1TiH(2) nano-composite system are 77.4 kJ mol(-1) H-2 and 137.5 J K-1 mol(-1) H-2, respectively. These values are in agreement with those obtained for a commercial MgH2 system measured under the same conditions. Nanostructure and catalyst may greatly improve the kinetics, but do not change the thermodynamics of the materials. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.