The high hydrogen storage capacity (10.5 wt.%) and release of hydrogen at a moderate temperature make LiAlH4 an appealing material for hydrogen storage. However, LiAlH4 suffers from slow kinetics and irreversibility. Hence, LaCoO3 was selected as an additive to defeat the slow kinetics problems of LiAlH4. For the irreversibility part, it still required high pressure to absorb hydrogen. Thus, this study focused on the reduction of the onset desorption temperature and the quickening of the desorption kinetics of LiAlH4. Here, we report the different weight percentages of LaCoO3 mixed with LiAlH4 using the ball-milling method. Interestingly, the addition of 10 wt.% of LaCoO3 resulted in a decrease in the desorption temperature to 70 °C for the first stage and 156 °C for the second stage. In addition, at 90 °C, LiAlH4 + 10 wt.% LaCoO3 can desorb 3.37 wt.% of H2 in 80 min, which is 10 times faster than the unsubstituted samples. The activation energies values for this composite are greatly reduced to 71 kJ/mol for the first stages and 95 kJ/mol for the second stages compared to milled LiAlH4 (107 kJ/mol and 120 kJ/mol for the first two stages, respectively). The enhancement of hydrogen desorption kinetics of LiAlH4 is attributed to the in situ formation of AlCo and La or La-containing species in the presence of LaCoO3, which resulted in a reduction of the onset desorption temperature and activation energies of LiAlH4.
Keywords: LaCoO3; LiAlH4; metal oxide; solid-state hydrogen storage.