**6.1 Role of magnesium in hydrogen storage**

In the recent decade, rapid advancement in nanostructuring techniques brought a new confidence in hydrogen storage applications. The hydrogen gas has been stored in metal hydride in the new generation technology in solid-state hydrogen storage. The physical and chemical properties of materials could be fundamentally varied with nano parameters. The research focused on nano-microstructures, which can play a vital role in hydrogen storage materials [23, 24]. To attain the maximum hydrogen storage capacity, Mg-based hydride materials are considered the most promising metallic content based on materials. Even though Mg has a higher storage capacity, the magnesium hydride's practical applications are still not reached because of its high working temperature and low kinetics. Besides, the high thermostability of bulk MgH2, such as Entropy (ΔS), Enthalpy (ΔH) with the decomposition, is 130JK-1 mol-1H2 75 kJ/mol H2 respectively, which means the temperature needed to reach 300 °C at the equilibrium pressure of 1 bar. So, it is required to optimize the stability between magnesium and hydrogen molecules that could increase the thermodynamics and kinetics properties. Reducing the particle size (nanoscale) and adding various catalyst materials are two critical factors in enhancing hydrogenation properties. The following factors that influence the absorptions rate are the physisorption rate of hydrogen gas on the magnesium alloy's surface, dissociation capacity, and nucleation growth of magnesium to the magnesium hydride [25, 26].
