Reversible hydrogenation/dehydrogenation performances of the Na_2LiAlH_6-Mg(NH_2)_2 system

摘要

Complex hydrides and Metal-N-H-based materials have attracted considerable attention due to their high hydrogen content. In this paper, a novel amide-hydride combined system was prepared by ball milling a mixture of Na_2LiAlH_6-Mg(NH_2)_2 in a molar ratio of 1:1.5. The hydrogen storage performances of the Na_2LiAlH_6-1.5Mg(NH_2)_2 system were systematically investigated by a series of dehydrogenation/hydrogenation evaluation and structural analyses. It was found that a total of ～ 5.08 wt% of hydrogen, equivalent to 8.65 moles of H atoms, was desorbed from the Na_2LiAlH_6-1.5Mg(NH_2)_2 combined system. In-depth investigations revealed that the variable milling treatments resulted in the different dehydro-genation reaction pathways due to the combination of Al and N caused by the energetic milling. Hydrogen uptake experiment indicated that only ～4 moles of H atoms could be reversibly stored in the Na_2LiAlH_6-1.5Mg(NH_2)_2 system perhaps due to the formation of AlN and Mg_3N_2 after dehydrogenation.