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

摘要

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 LiNH_2/MgH_2 mixtures with initial molar ratios ranging from 1.5:1 to 3:1, followed by de/rehydriding at 200℃. It was found that the hydrogen storage capacity of the system was highly dependent on the initial phase ratio of the LiNH_2/MgH_2 mixture. An optimum hydrogen capacity of about 5 wt% was achieved in the 2.15:1 LiNH_2/MgH_2 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.