Improvement of hydrogen-storage properties of MgH_2 by addition of Li_3N, LiBH_4, Fe and/or Ti

摘要

In order to increase hydrogen storage capacity of MgH_2-based materials, Li_3N, LiBH_4, Fe, and/or Ti were added. Mixtures with compositions of 50MgH_2-50Li_3N, 40Mg-10MgH_2-50Li_3N, 68MgH_2-17LiBH_4-15Fe, and 70MgH_2-17LiBH_4-13Ti were prepared by reactive mechanical grinding and their hydrogen-storage properties were examined. 40Mg-10MgH_2-50Li_3N after hydriding-dehydriding cycling contains Mg_3N_2, LiMgN, LiOH, and MgO, LiH, and NH_3·2H_2O, suggesting a reaction of 6Mg + 4MgH_2 + 4Li_3N + 23H_2O → Mg_3N_2 + LiMgN + 11 LiOH + 3NH_3· 2H_2O + 6MgO + 7H_2. 70MgH_2-17LiBH_4-13Ti after hydriding-dehydriding cycling contained MgH_2, TiH_(1.924), Mg, and MgO. Among the samples studied, 70MgH_2-17LiBH_4-13Ti had the highest hydriding rate in the beginning. The as-milled 70MgH_2-17LiBH_4-13Ti sample absorbed 3.33 wt% H for 5 min, 3.83 wt% H for 10 min, and 3.94 wt% H for 60 min at 573 K under 12 bar H_2.