Activity and capacity of hydrogen storage alloy Mg₂NiH₄ produced by hydriding combustion synthesis

A high activity and a large capacity of hydrogen storage alloy Mg₂NiH₄ produced by hydriding combustion synthesis were investigated by means of differential scanning calorimeter (DSC) and pressure-composition isotherms (PCT). The results showed that the product of Mg₂NiH₄ from the hydriding combustion synthesis has enough activity to the hydriding reaction and the amount of hydrogen absorbed by the product reached the maximum (3.4-3.6%) mass near the theoretical value just after synthesis without any activation process. This kind of activity and capacity of hydrogen storage are not only stable, but also tolerant of high temperature of 850 K. PCT results give some phenomenon of three phases existing in isotherms. The relationships between the equilibrium plateau pressure and the temperature were Log P (0.1 MPa) = -3525/T+6.667 for hydriding and Log P (0.1 MPa) = -3724/T+6.883 for dehydriding.