| dc.description.abstract | H2 is viewed as one of the promising clean fuels of the future. The H2 economy involves three important areas: production, storage, and use.Among them, developing effective H2 storage methods and materials for transportation is a key challenge for basic research and a crucial factor in achieving the H2 economy.
LiBH4 is a potential H2 storage material owing to its high theoretical H2 capacity (18.5 wt% H2). In this study, the as-received LiBH4 is modified by Pd-Ni(OH)x additives and their dehydrogenation properties are investigated by a technique of temperature programmed reduction (TPR), thermogravimetric analyzer (TGA), and temperature programmed dehydrogenation-mass spectrometers (TPD-MS). The phase structures of the modified LiBH4 before and after dehydrogenation are analyzed by the X-ray powder diffraction (XRD) method. For the Pd-Ni(OH)x modified
LiBH4, it presents superior dehydrogenation kinetics, and its Tm (the main dehydrogenation peak) is changed from 740 to 370 K, suggesting that the Pd-Ni(OH)x additive can effectively reduce LiBH4 dehydrogenation temperature. Addition of Pd-Ni(OH)x into LiBH4 changes their dehydrogenation properties and reaction kinetics. When the amount of LiBH4 in the mixture increases from 0.33 to 0.67 (LiBH4: Pd-Ni(OH)x = 1:2 to 2:1 for C2 and C0.5), their desorption capacity increases and Tm decreases from 1.5 to 6.5 wt% and 740 to nearby 340 K, respectively. Among them, the C0.5 sample presents the superior dehydrogenation kinetics, and after dehydrogenation, LiBH4, Pd, Ni and Ni(OH)2 in the C0.5 sample transfer to Li6B4O9, PdB2, and Ni, respectively.
For the dehydrogenation of various samples measured at 373 K for 1 h, the desorption capacity of modified LiBH4 is larger than that of un-modified one, implying that the modified sample displays good desorption kinetics at low temperatures. Moreover, in order to investigate the [OH]- group effect on their dehydrogenation, Pd-Ni(OH)x is heat treated at 473 K for 1 h, and Ni(OH)2 phase transfers to NiO. For the dehydrogenation of C0.5 and C0.5-H (LiBH4 modified by heated catalysts), the onset temperature of C0.5-H is higher than that of C0.5 while their desorption capacities are almost the same. This indicates that the [OH]- group does not influence the H2 capacities, but strongly affect the dehydrogenation kinetics of the mixtures. As a result, the Pd-Ni(OH)x-modified LiBH4 is a promising material for H2 storage materials.
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