Reaction steps in the Li–Mg–N–H hydrogen storage system

The reaction steps in mixtures of 2LiNH2–MgH2 during hydrogen sorption are investigated. Differential scanning calorimetry experiments at various H2 pressures show that the initial decomposition comprises several steps and their transition temperature depends on the applied hydrogen pressure. During the first desorption of the powders, an exothermic phase transition takes place where Mg(NH2)2Mg(NH2)2 is partially formed. This is followed by an endothermic decomposition that yields hydrogen. The addition of 2 mol% TiCl3TiCl3 to the initial 2LiNH2–MgH2 mixture does not affect the exothermic phase transition but the hydrogen release shifts to lower temperatures. Adding 2 mol% TiCl3 after two hydrogenation cycles to the material has no effect on the desorption properties.