Hydrogen desorption kinetics of the destabilized LiBH4[sbnd]AlH3 composites.

LiBH 4 can be destabilized by AlH 3 addition. In this work, the hydrogen desorption kinetics of the destabilized LiBH 4 AlH 3 composites were investigated. Isothermal hydrogen desorption studies show that the LiBH 4 + 0.5AlH 3 composite releases about 11.0 wt% of hydrogen at 450 °C for 6 h and behaves better kinetic properties than either the pure LiBH 4 or the LiBH 4 + 0.5Al composite. The apparent activation energy for the LiBH 4 decomposition in the LiBH 4 + 0.5AlH 3 composite estimated by Kissinger's method is remarkably lowered to 122.0 kJ mol −1 compared with the pure LiBH 4 (169.8 kJ mol −1 ). Besides, AlH 3 also improves the reversibility of LiBH 4 in the LiBH 4 + 0.5AlH 3 composite. For the LiBH 4 + x AlH 3 ( x = 0.5, 1.0, 2.0) composites, the decomposition kinetics of LiBH 4 are enhanced as the AlH 3 content increases. The sample LiBH 4 + 2.0AlH 3 can release 82% of the hydrogen capacity of LiBH 4 in 29 min at 450 °C, while only 67% is obtained for the LiBH 4 + 0.5AlH 3 composite in 110 min. Johnson−Mehl−Avrami (JMA) kinetic studies indicate that the reaction LiBH 4 + Al → ‘Li Al B’ + AlB 2 + H 2 is controlled by the precipitation and subsequently growth of AlB 2 and Li Al B compounds with an increasing nucleation rate. [ABSTRACT FROM AUTHOR]