Effect of BaH2 on the hydrogen storage properties of Mg(NH2)2-LiH

Abstract

The Mg(NH₂)₂-2LiH composite has garnered extensive attention on account of its high theoretical hydrogen storage capacity (5.6 wt%) and favorable thermodynamic properties (ca. 40 kJ/mol-H₂). However, the sluggish kinetics restricts its practical application. In this study, we investigated in detail the effect of BaH₂ doping on the hydrogen absorption and desorption properties of Mg(NH₂)₂-2LiH. Experimental results demonstrated that the incorporation of BaH₂ significantly enhances the hydrogen absorption/desorption kinetic performance compared to the pristine sample. The optimum overall performance was achieved for the sample doped with 0.05 BaH₂. Its initial hydrogen release temperature and peak dehydrogenation temperature were decreased by 30 and 20 °C, respectively. The rate of hydrogen release during isothermal dehydrogenation at 160 °C was twice as fast as that of the undoped sample, and the interrelated activation energy was reduced from 112.8 to 72.2 kJ/mol. Additionally, the mechanism underlying improvement of the hydrogen storage performance in the Mg(NH₂)₂-2LiH composite by BaH₂ was elucidated.