Study On The Hydrogen Storage Properties Of LiAlH₄and Composite System

Hydrogen is treated as the most ideal green energy in the future due to its compellingadvantages such as high energy density, renewability and environment-friendliness. Highefficient hydrogen storage technology is a crucial issue that should be well solved before thewidespread application of hydrogen energy. Mental complex hydrides like LiAlH₄have beenstudied intensively as new types of hydrogen storage materials because of its high hydrogenstorage capacity.As-procured LiAlH₄were used in this study. Orthogonal experiment was adopted toinvestigate the influence of ball-milling process to the hydrogen desorption properties ofLiAlH₄. The results showed that the most sensitive influencing factor of hydrogen desorptionproperties was milling time under the same reaction conditions. LiAlH₄had the optimumperformance when the weight ratio of ball to power was40:1, the weight ratio of big ball tosmall ball was0.5:1and milling time was1hour.The study on LiAlH₄/NH₄Cl system included the composition ratio and rare earthcompounds doping research. Research showed that the hydrogen desorption properties ofLiAlH₄/NH₄Cl system was better than the one of LIAlH₄. LiAlH₄/NH₄Cl system had the bestperformance when the ratio of LiAlH₄and NH₄Cl was1:1. The photos of SEM showed thatamount of pores appeared on the surface of the ball-milled LiAlH₄/NH₄Cl sample. Study onrare earth compounds doping showed that the hydrogen release time of LiAlH₄/NH₄Cl wasadvanced by doping La₂O₃, and the hydrogen release time of LiAlH₄/NH₄Cl began from17min by doped2mol%La₂O₃, which earlier than undoped LiAlH₄/NH₄Cl10min. Theimprovement of LiAlH₄/NH₄Cl hydrogen desorption properties was remarkable by dopingCeO₂. The amount of hydrogen desorption of1mol%CeO₂doped LiAlH₄/NH₄Cl was higherthan the undoped one as much an0.3wt.%, besides, the hydrogen temperature was also loweras10℃. The addition of LaCl₃did not play positive role, but reduced dehydrogenation rateand the amount of hydrogen. Hydrogen release time was also delayed.The research on LiAlH₄/MgH₂system showed that, LiAlH₄/MgH₂had earlier hydrogen release time and lower hydrogen temperature when the mole ratio of LiAlH₄and MgH₂was1:1.5,1:2, but the amount of hydrogen desorption was not improved compared with LiAlH₄.However, the sample, which mole ratio of LiAlH₄and MgH₂was1:0.5, had higher amount ofhydrogen desorption than LiAlH₄. The doping of rare earth compounds, such as LaCl₃, La₂O₃+,CeO₂,improved the hydrogen desorption ability of LiAlH₄/MgH₂. Especially, hydrogentemperature of LiAlH₄/MgH₂system was reduced as much as30℃by doping5mol%LaCl₃,while the amount of hydrogen desorption was increased fifteen percent by doping3mol%La₂O₃. Based on the microstructure analysis of LiAlH₄/MgH₂system, it could be foundthat doping catalyst would reduce the particle size and improve the dispersion of milledsample. It was the main reason of the hydrogen desorption performance of LiAlH₄/MgH₂system could be improved.