Synergistic hydrogen desorption properties of the 4LiAlH₄+ Mg₂NiH₄composite

Mg₂NiH₄was prepared by hydriding combustion synthesis (HCS) method firstly. Then, the as prepared Mg₂NiH₄was mechanically milled with LiAlH₄to form a novel composite of 4LiAlH₄+ Mg₂NiH₄. Hydrogen storage properties and reaction mechanism of the 4LiAlH₄+ Mg₂NiH₄composite during hydrogenation/dehydrogenation have been investigated systematically by pressure-composition-temperature (PCT), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements. The microstructure of the composite has been investigated by scanning electron microscopy (SEM). The experimental results show that there is a mutual destabilization effect between Mg₂NiH₄and LiAlH₄during hydrogen desorption. Mg₂NiH₄can promote the decomposition of LiAlH₄in both of the ball milling process and the thermal desorption process. Conversely, the in situ formed Al from the decomposition of LiAlH₄can destabilize Mg₂NiH₄via a new reaction pathway with lower activation energy. Moreover, the 4LiAlH₄+ Mg₂NiH₄composite shows ultrafast re-hydrogenation kinetics, and the re-hydrogenation mechanism has been revealed.