Hydrogen sorption properties of M0.2Ca0.8MgH4 (M = Li, Na).

The synthesis, thermodynamic destabilisation and hydrogen sorption properties of the M 0.2 Ca 0.8 MgH 4 hydride system, where (M = Na or Li) have been investigated. Samples were mechanically milled under argon for 5, 10 and 15 h; then characterised by X-ray diffraction (in/ex-situ), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) coupled with a mass spectrometer (MS). On Li and Na substitution into Ca–Mg–H ternary hydride, diffraction peaks shifted to higher angles. 2 and 3 endothermic reactions were observed for the Li 0.2 Ca 0.8 MgH 4 and Na 0.2 Ca 0.8 MgH 4. The maximum amount of hydrogen release was achieved for the 5 h milled Na 0.2 Ca 0.8 MgH 4 hydride from 298 °C to 386 °C accounting for 3.5 wt % of H 2. • M 0.2 Ca 0.8 MgH 4 (M = Na, Li), was prepared by mechanical milling under argon alone. • Li 0.2 Ca 0.8 MgH 4 samples show a lattice contraction in the main Ca 19 Mg 8 H 54 phase. • 3.5 wt % of H 2 at 329 °C was achieved on the 5 h milled Na 0.2 Ca 0.8 MgH 4. • Li and Na incorporations enhance the sorption properties of Ca–Mg–H hydride. [ABSTRACT FROM AUTHOR]