Effects of NbF 5 addition on the de/rehydrogenation properties of 2LiBH 4/MgH 2 hydrogen storage system

Abstract

2LiBH 4/MgH 2 system is considered as one of the prominent high capacity hydrogen storage materials. However, its absorption/desorption kinetics has to be further improved for the practical application. In this paper, we investigated the effects of NbF 5 addition by ball milling on the de/rehydrogenation properties of 2LiBH 4/MgH 2 system. The results show that NbF 5 additive can lower the desorption temperature and improve the reaction kinetics of 2LiBH 4/MgH 2 system effectively. The 2LiBH 4 + MgH 2 + 0.05NbF 5 composite exhibits a good cycling de/rehydrogenation property. In first 15 cycles, the average hydrogen absorption and desorption capacities of the composite are about 8.97 and 8.33 wt %, respectively. Desorption thermal analysis indicates that the activation energies of 2LiBH 4 + MgH 2 + 0.05NbF 5 composite are 100.3 kJ/mol for first decomposition reaction and 127.5 kJ/mol for second decomposition reaction. The possible mechanism of the effects of NbF 5 additive for the improved de/rehydrogenation properties of 2LiBH 4/MgH 2 system is also discussed. © 2012 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.