Investigation on the gaseous hydrogen storage properties of as-cast Mg95-Al5Y (x = 0–5) alloys

The kinetics of hydrogen absorption/desorption of Mg-based materials are very sluggish and the thermodynamics of reaction is also poor. In order to improve the kinetics and thermodynamics of Mg-based materials, the Mg95-xAl5Yx (x = 0–5) composites were successfully prepared with the help of vacuum induction melting. Then, the isothermal hydrogen storage performances were researched by using Sievert apparatus and the non-isothermal hydrogen storage properties were measured by DSC (Differential scanning calorimetry) and TPD (Temperature programmed dehydrogenation). The phase components were determined by X-ray diffraction, and the observation of micromorphology and the determination of crystal state were completed by using SEM (Scanning electron microscope), TEM (Transmission electron microscope) and SAED (Selected area electron diffraction), respectively. According to the result, the substitution of Y for Mg results in the formation of the second phase Mg24Y5 which transforms into the magnesium hydride and high thermal stability yttrium hydrides after hydrogenation. With the increase of Y content from 0 to 5, the absolute value of dehydrogenation activation energy Eade decreases from 155.562 ± 2.29 to 79.622 ± 5.61 kJ/mol. Considering the standard errors of fitting and measurement, the influence of Y substitution on the thermodynamics parameters is not obvious. However, the initial decomposition temperature of the Mg–Al-based alloy can be reduced by 40.2 K through the addition of yttrium.