14102
J. Phys. Chem. B 2007, 111, 14102-14106
Reversible Hydrogen Storage Property and Structural Analysis for Face-Centered Cubic Hydride Mg0.82Zr0.18H2 Prepared by Gigapascal Hydrogen Pressure Method Tomoaki Takasaki,* Daisuke Kyoi, Naoyuki Kitamura, Shigeo Tanase, and Tetsuo Sakai* Research Institute for Ubiquitous Energy DeVices, National Institute of AdVanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan ReceiVed: June 7, 2007; In Final Form: October 22, 2007
The face-centered cubic (fcc) type magnesium-zirconium hydride (Mg0.82Zr0.18Hx) was synthesized by means of the ultrahigh pressure (UHP) technique, which could generate 8 GPa of hydrogen pressure. The differential scanning calorimeter (DSC) measurements indicated that the fcc phase exhibited reversible hydrogen releasing and restoring properties under 0.5 MPa of hydrogen pressure. On the pressure-composition isotherms, the released and restored hydrogen capacities were estimated to be 3∼3.5 wt %. The Rietveld analysis for synchrotron X-ray diffraction (XRD) data showed that the fcc phase had around 70 wt % mass fraction and was preserved without decomposition during hydrogen releasing and restoring cycles.
1. Introduction Clean energy sources for alternating fossil fuel have to be developed in order to overcome the growing concern about environmental pollution and depletion of oil resources. Hydrogen is a clean and exhaustless energy source. However, large volumes are necessary to store gaseous hydrogen, so many researchers have studied hydrogen storage materials to realize a compact and safe hydrogen storage system.1 The important requirements for hydrogen storage materials would be high hydrogen capacity (>5.5 wt %) and reversible hydrogen storage properties with low releasing temperature (
