Improved hydrogen sorption characteristics of Mg(NH2)2- 2 LiH/Li4BH4(NH2)3 using SrH2 and MgF2 auto-catalyst

Abstract

The destabilization of the Mg(NH2)(2)-2LiH/Li4BH4(NH2)(3) using an alkaline earth fluoride as additive such as SrF2 has been discussed and described in the present investigation. The advantage of the alkaline earth fluoride (SrF2) is that it can form two different kinds of catalysts, MgF2 and SrH2, by reacting with the MgH2 component during annealing, however, it is un-reacted when ball milled. The impact of (SrH2+MgF2) on the hydrogen storage performance of Mg(NH2)(2)-2LiH/Li4BH4(NH2)(3) has been found to be quite effective as compared to other catalysts for hydrogen sorption. The onset desorption temperature for Mg(NH2)(2)-2LiH/Li4BH4(NH2)(3) catalyzed by SrH2+MgF2 has been found to be 91.22 degrees C, whereas the temperature for uncatalyzed Mg(NH2)(2)-2LiH/Li4BH4(NH2)(3) is 135.92 degrees C. The formation of auto-catalysts (SrH2+MgF2) with the in-situ formed Li4BH4(NH2)(3) is much more effective on 1:2 Mg(NH2)(2)-LiH compared to (SrH2+MgF2)catalyzed 1:2 Mg(NH2)(2)-LiH. The (SrH2+MgF2)-catalyzed Mg(NH2)(2)- 2 LiH/Li4BH4(NH2)(3) shows promising kinetics. It desorbs and absorbs 3.51 wt% and 4.21 wt% H-2 in 15 min at 170 degrees C respectively. The cyclic stability of (SrH2+MgF2)-catalyzed Mg(NH2)(2)-2 LiH/Li4BH4(NH2)(3) has been found to be very stable up to 10 cycles. The recovery rate was found to be 96.49 % from 10(th) to 1(st) cycle of de/re-hydrogenation.