Structural characterization and hydrogen storage properties of MgH2–Mg2CoH5 nanocomposites

Mixtures of XMg–Co containing different amounts of Mg (X = 2, 3 and 7) were reactive milled under hydrogen atmosphere. 2Mg–Co only formed the Mg 2 CoH 5 complex hydride, while the mixtures 3Mg–Co and 7Mg–Co formed different contents of Mg 2 CoH 5 and MgH 2 . Their structural features and hydrogen storage properties were analyzed by different techniques. In-situ synchrotron X-ray diffraction, combined with thermal analysis techniques, (differential scanning calorimetry, thermal gravimetric analysis and quadrupole mass spectrometer) was carried out to observe the behavior of the MgH 2 –Mg 2 CoH 5 mixtures during the first H-desorption. It was found that the presence of the Mg 2 CoH 5 complex hydride has a beneficial effect on the first H-desorption of the MgH 2 . Additionally, after first desorption, conventional hydrogenation under high pressure and high temperature of 3Mg–Co and 7Mg–Co samples led to the formation of the Mg 6 Co 2 H 11 complex hydride. The presence of Mg 6 Co 2 H 11 considerably impaired the desorption properties of the nanocomposites.