Improved hydrogen storage performance of Li–Mg–N–H materials by optimizing composition and adding single-walled carbon nanotubes

A systematic investigation on the hydrogen storage properties of Li–Mg–N–H materials with various compositions was performed. Li–Mg–N–H hydrogen storage materials were prepared by mechanically milling LiNH2/MgH2 mixtures with initial molar ratios ranging from 1.5:1 to 3:1, followed by de/rehydriding at 200∘C. It was found that the hydrogen storage capacity of the system was highly dependent on the initial phase ratio of the LiNH2/MgH2 mixture. An optimum hydrogen capacity of about 5 wt% was achieved in the 2.15:1 LiNH2/ MgH2 mixture. Different carbon materials, such as the single-walled carbon nanotubes (SWNTs), multi-walled carbon nanotubes, graphite and activated carbon, were used as additive to improve the hydrogen storage performance. It was found that the dehydriding kinetics of the Li–Mg–N–H material could be markedly improved by adding a small amount of SWNTs, especially in the as-prepared state.