Thermodynamic and Kinetic Assessment of Ni‐Substituted Mg‐Based Alloys for Hydrogen Storage

The primary advantages of Mg‐based hydrogen storage alloys lie in their high theoretical hydrogen storage capacity. However, their hydrogen absorption and desorption require higher temperatures and exhibit poor kinetics, limiting their practical application. In this study, the Y 5 Mg 95‐ x Ni x ( x = 5, 10, 15) alloys are prepared. These alloys are fully activated by a single hydrogenation/dehydrogenation cycle, and the thermal stability of MgH 2 is significantly reduced. The initial dehydrogenation temperature of MgH 2 decreases from 551.5 K ( x = 5) to 533.6 K ( x = 10). Hydrogen desorption kinetics improve with increasing Ni content. The time required to desorb 3 wt% hydrogen at 260 °C decreases from 1872 s ( x = 5) to 845 s ( x = 15). However, higher Ni content also lead to a decrease in hydrogenation/dehydrogenation capacity. Furthermore, increasing Ni content reduces the dehydrogenation activation energy. As the Ni content increases from x = 5 to 15, the activation energy decreases from 80.5 to 70.29 kJ mol −1 , which is responsible for the improved hydrogen storage performance resulting from Ni substitution.