YMgGa as a hydrogen storage compound

The hydrogen absorption and desorption properties of the recently found ternary phase YMgGa have been studied. This compound absorbs 2.2 wt% hydrogen during the first cycle, but only 1.1 wt% can be stored reversibly for the following cycles under the applied pressure and temperature conditions. Hydrogen absorption and desorption properties were investigated by measuring the thermal desorption spectra and the pressure-composition isotherms while the crystal structure was determined using X-ray diffraction (XRD). The compound absorbs hydrogen at pressures above 0.2 MPa and 250 °C by decomposing into YH3 and MgGa. This reaction is reversed when heating the hydride in a He atmosphere; hydrogen is released and the YMgGa phase is partially recovered together with YGa2 and YH2. The reformation of YMgGa occurs at temperatures below 450 °C on the expenses of hydrogen desorption from YH2. This is not expected under these temperature conditions as YH2 normally does not desorb hydrogen below 800 °C.