Hydrogen desorption kinetics of the destabilized LiBH4-AlH3 composites

摘要

LiBH4 can be destabilized by AlH3 addition. In this work, the hydrogen desorption kinetics of the destabilized LiBH4-AlH3 composites were investigated. Isothermal hydrogen desorption studies show that the LiBH4 + 0.5AlH(3) composite releases about 11.0 wt% of hydrogen at 450 degrees C for 6 h and behaves better kinetic properties than either the pure LiBH4 or the LiBH4 + 0.5Al composite. The apparent activation energy for the LiBH4 decomposition in the LiBH4 + 0.5AlH(3) composite estimated by Kissinger's method is remarkably lowered to 122.0 kJ mori compared with the pure LiBH4 (169.8 kJ moll. Besides, AlH3 also improves the reversibility of LiBH4 in the LiBH4 + 0.5AlH(3) composite. For the LiBH4 + xAlH(3) (x = 0.5, 1.0, 2.0) composites, the decomposition kinetics of LiBH4 are enhanced as the AlH3 content increases. The sample LiBH4 + 2.OAlH3 can release 82% of the hydrogen capacity of LiBH4 in 29 min at 450 degrees C, while only 67% is obtained for the LiBH4 + 0.5AlH(3) composite in 110 min. Johnson Mehl Avrami (JMA) kinetic studies indicate that the reaction LiBH4 + Al -> 'Li-Al -B' + AlB2 + H-2 is controlled by the precipitation and subsequently growth of AlB2 and Li-Al B compounds with an increasing nucleation rate. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.