Effects of Stoichiometry on the H -Storage Properties of Mg(NH ) -LiH-LiBH Tri-Component Systems.

The hydrogen desorption pathways and storage properties of 2 Mg(NH ) -3 LiH-xLiBH samples (x=0, 1, 2, and 4) were investigated systematically by a combination of pressure composition isotherm (PCI), differential scanning calorimetric (DSC), and volumetric release methods. Experimental results showed that the desorption peak temperatures of 2 Mg(NH ) -3 LiH-xLiBH samples were approximately 10-15 °C lower than that of 2 Mg(NH ) -3 LiH. The 2 Mg(NH ) -3 LiH-4 LiBH composite in particular began to release hydrogen at 90 °C, thereby exhibiting superior dehydrogenation performance. All of the LiBH -doped samples could be fully dehydrogenated and re-hydrogenated at a temperature of 143 °C. The high hydrogen pressure region (above 50 bar) of PCI curves for the LiBH -doped samples rose as the amount of LiBH increased. LiBH changed the desorption pathway of the 2 Mg(NH ) -3 LiH sample under a hydrogen pressure of 50 bar, thereby resulting in the formation of MgNH and molten [LiNH -2 LiBH ]. That is different from the dehydrogenation pathway of 2 Mg(NH ) -3 LiH sample without LiBH , which formed Li Mg N H and LiNH , as reported previously. In addition, the results of DSC analyses showed that the doped samples exhibited two independent endothermic events, which might be related to two different desorption pathways.