Effect of the temperature and of the catalyst on the hollow particle formation in the Mg composites

•Effect of extended H2 sorption cycles of MgH2 powders with catalyst.•Kinetics of reaction with hydrogen and maximum storage capacity during cycling.•Worm-like structures and empty hollow particles MgO shells after H2 cycling.

The high H2 storage capacity, the reversibility and the low cost make magnesium hydride a promising material for hydrogen storage at the solid state. The stability of these materials under H2 cycling has been tested in this paper. Moreover, the morphological modifications of MgH2 particles during hydrogen cycling have been studied. In particular, it is discussed how experimental parameters such as the temperature and the nature of the catalyst could affect the morphological changes occurring after cycling for MgH2 powder ball milled with Fe or Nb2O5. The cycled sample, presents the formation of hollow particles constituted by MgO shell and the absence of the catalyst in most of the particles has been observed. Ball milled MgH2 with and without catalyst has been prepared and different thermal treatments have been performed in a Sievert's type apparatus. Scanning electron microscope has been used for the observation of the powders.