The enhanced hydrogen storage performance of (Mg-B-N-H)-doped Mg(NH_2)-2LiH system

摘要

Doping Mg(NH_2)_2-2LiH by Mg_2(BH_4)_2(NH_2)_2 compound exhibits enhanced hydrogen de/re-hydrogenation performance. The peak width in temperature-programmed desorption (TPD) profile for the Mg(NH_2)_2-2LiH-0.1Mg_2(BH_4)_2(NH_2)_2 was remarkably shrunk by 60 ℃ from that of pristine Mg(NH_2)_2-2LiH, and the peak temperature was lowered by 12 ℃ from the latter. Its isothermal dehydrogenation rate was greatly improved by five times from the latter at 200 ℃. XRD, FTIR and NMR analyses revealed that a series of reactions occurred in the dehydrogenation of the composite. The prior interaction between LiH and Mg-B-N-H yielded intermediate LiBH_4, which subsequently reacted with Mg(NH_2)_2 and LiH in molar ratio of 1:6:9 to form Li_2Mg_2(NH)_3 and Li_4BN_3H_(10) phases. The observed 6Mg(NH_2)_2-9LiH -LiBH_4 combination dominated the hydrogen release and soak in the composite system, and enhanced the kinetics of the system.