Effects Of Perovskite Metal Oxides And Rare Earth Sulfides On Hydrogen Storage Properties Of LiBH₄

Among the lightweight hydrogen storage materials, Li BH4(theoretical hydrogen storage capacity are 18.5 wt.%), have triggered enormous research works because of their high hydrogen storage capacitie. However, the disadvantages of high hydrogen adsorption-desorption temperature and slow hydrogen adsorption-desorption kinetics limit their practical applications. In this thesis, metal oxides with perovskite structures and rare earth sulfides used as additives were introduced into Li BH4 prepared by mechanical ball milling method. The hydrogen storage performances of the composite materials were investigated. The hydrogen adsorption-desorption reaction routes and the effect mechanisms of the additives in the adsorption-desorption processes were further studied.The hydogen storage performances of the prepared composite material Li BH4 introduced perovskite metal oxides La Fe O3, Mg Ti O3 and Ba Ti O3 presented obvious improvements. The initial hydrogen desorption temperature of the Li BH4 introduced La Fe O3, Mg Ti O3 and Ba Ti O3 decreased by 25 ℃, 25 ℃and 65 ℃, respectively. The hydrogen desorption activition energy of the materials simultaneously decreased by 88.82 k J/mol, 37.44 k J/mol and 16.77 k J/mol, respectively. Improve hydrogen storage properties were mainly due to that the addition of three additives could react with Li BH4 during the desorption reaction process and change Li BH4 desorption path, so that the entire desorption activation energy decreases.The effects of Ce2S3 on the hydrogen storage properties of the Li BH4 was studied. It was concluded that the initial hydrogen desorption temperature of the Li BH4 with Ce2S3 was provided with the decreasing amount of 125 ℃. The activation energy of dehydrogenation decreased by 24 k J/mol. Within 3000 s at 400 ℃, the Li BH4+20 wt.% Ce2S3 composite materials can release about 4.0 wt% hydrogen. Meanwhile, the Li BH4+20 wt.% Ce2S3 composite materials exhibited a much faster re-hydrogenation and higher hydrogen absorption amount with 3.6 wt% after the 4th cycle. The main reasons for the improvement of hydrogen storage performance were Ce2S3 as a reactant reacted with Li BH4, formed Li2 S and Ce B6 and changed desorption path. Meanwhile, the formation of Li2 S and Ce B6 which synergistic increase the dehydrogenation and reversibility of the Li BH4 system.