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LiBH 4 , as a potential material with the highest reversible hydrogen storage capacity for hydrogen vehicle applications, has always been hydrogenated and dehydrogenated in the liquid state. In this study, we demonstrate, for the first time, that 8.3 wt % hydrogen uptake can be obtained from the LiBH 4 + MgH 2 system in the solid state through nanoengineering and mechanical activation. Hydrogen release, although slower than uptake, can also be attained in the solid state. All of these enhancements are achieved without any catalysts, which underscores the effectiveness of nanoengineering and mechanical activation as well as the opportunity for further improvements in the future.

The decomposition of lithium amide (LiNH2) to lithium imide (Li2NH) and ammonia (NH3) with and without high-energy ball milling is investigated to lay a foundation for identifying methods to enhance the hydrogen uptake/release of the lithium amide and lithium hydride mixture. A wide range of analytical instruments are utilized to provide unambiguous evidence of the effect of mechanical activation. It is shown that ball milling reduces the onset temperature for the decomposition of LiNH2 from 120 degrees C to room temperature. The enhanced decomposition via ball milling is attributed to mechanical activation related to the formation of nanocrystallites, the reduced particle size, the increased surface area, and the decreased activation energy. The more mechanical activation there is, then the more improvement there is in enhancing the decomposition of LiNH2. It also is found that the activation energy for the decomposition of LiNH2 without ball milling is 243.98 kJ/mol, which is reduced to 222.20 kJ/mol after ball milling at room temperature for 45 min and is further reduced to 138.05 kJ/mol after ball milling for 180 min. The rate of the isothermal decomposition at the later phase of the LiNH2 decomposition is controlled by diffusion of NH3 through the Li2NH layer.