Effects of Metal Borohydrides on the Dehydrogenation Kinetics of the Li–Mg–N–H Hydrogen-Storage System

The combination of magnesium amide and lithium hydride represents a category of solid hydrogen-storage system with moderate hydrogen-storage conditions and good reversibility. At a molar ratio of 1:2 for the amide and hydride [Mg­(NH2)2-2LiH], the dehydrogenation kinetics of the system can be effectively accelerated by LiBH4. In this paper, the effects of kinetic enhancement were studied by doping the amide-hydride system at 1:2 molar ratio with NaBH4 and Mg­(BH4)2 along with LiBH4. Compared to the pristine system, the activation energies for the dehydrogenation were decreased by all three metal hydrides in the order of Mg­(BH4)2 > LiBH4 > NaBH4. The mechanism for the kinetic improvement of Mg­(BH4)2 and NaBH4 was investigated.