International Journal of Hydrogen Energy, Vol.44, No.35, 19294-19301, 2019
Catalytic effects of Mg(BH4)(2) on the desorption properties of 2LiNH(2)-MgH2 mixture
2LiNH(2)-MgH2 possesses a higher theoretical hydrogen storage and favorable thermodynamics, considering as one of the most promising materials. Catalysis is significantly effective in improving the kinetics properties and thermodynamic destabilization of Li-Mg-N-H systems. Different amount (0.05, 0.1, 0.2, 0.3 at.%) of Mg(BH4)(2) were added to enhance the hydrogen storage properties of the 2LiNH(2)-MgH2 system. During the ball milling, reactions happen between Mg(BH4)(2) and LiNH2, converting to Mg(NH2)(2) and Li-4(BH4)(NH2)(3). The in-situ formed Mg(NH2)(2) transforms from crystalline state to amorphous state during ball milling, and then reverts during the dehydrogenation. The dehydrogenation process of 2LiNH(2)-MgH2-xMg(BH4)(2) (x = 0, 0.05, 0.1, 0.2, 0.3 at.%) shows an obvious decrease in the initial dehydrogenation temperature and an enhancement in dehydrogenation kinetics, which was evidenced by the activation energy. It seems to be the catalytic effect of in-situ formed Li4(BH4)(NH2)3, as an intermediate during dehydrogenation process, promoting the hydrogen releasing. The desorption process of 2LiNH(2)-MgH2-0.3 Mg(BH4)(2) at different stages is revealed. The 0.05 Mg(BH4)(2)-added sample possesses a good cycle stability during the during the dehydrogenation/hydrogenation cycles at lower temperature (240 degrees C). (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.