Abstract
A detailed analysis of the dehydrogenation mechanism of LiBH4/xLiAlH4 (x = 0.5, 1, 2) composites was performed by thermogravimetry (TG), differential scanning calorimetry (DSC), mass spectral analysis (MS), powder X-ray diffraction (XRD) and scanning electronic microscopy (SEM), along with kinetic investigations using a Sievert-type apparatus. The results show that the dehydrogenation pathway of LiBH4/xLiAlH4 had a four-step character. The experimental dehydrogenation amount did not reach the theoretical expectations, because the products such as AlB2 and LiAl formed a passivation layer on the surface of Al and the dehydrogenation reactions associated with Al could not be sufficiently carried out. Kinetic investigations discovered a nonlinear relationship between the activation energy (Ea) of dehydrogenation reactions associated with Al and the ratio x, indicating that the Ea was determined both by the concentration of Al produced by the decomposition of LiAlH4 and the amount of free surface of it. Therefore, the amount of effective contact surface of Al is the rate-determining factor for the overall dehydrogenation of the LiBH4/xLiAlH4 composites.
Highlights
With the exhaustion of traditional fossil fuels and environmental pollution, the exploration of clean energy is attracting more and more attention
The second step dehydrogenation of completely decompose in the range of 350 °C to 435 °C and the product LiH began to react with Al to produce LiAl and H2 based on Equation (8) near 435 °C
The dehydrogenation pathway of LiBH4/xLiAlH4 (x = 0.5, 1, 2) composites had a four-step character: The first step involved the decomposition of LiAlH4 to form Li3 AlH6, Al and H2 and character: The first step involved the decomposition of LiAlH4 to form Li3AlH6, Al and H2 and partial decomposition of Li3 AlH6 to form LiH and Al while releasing H2
Summary
With the exhaustion of traditional fossil fuels and environmental pollution, the exploration of clean energy is attracting more and more attention. Hydrogen is recognized as one of the most promising clean energy sources. The lack of efficient hydrogen storage materials is a formidable problem that hinders the practical application of hydrogen [1,2,3]. LiBH4 is of special interest as materials for solid-state hydrogen storage due to its high theoretical hydrogen storage capacity of 18.5 wt.%.
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