Abstract
Research for suitable hydrogen storage materials is an important ongoing subject. LiBH4–Al mixtures could be attractive; however, several issues must be solved. Here, the dehydrogenation reactions of surface-oxidized 2LiBH4 + Al mixtures plus an additive (TiF3 or CeO2) at two different pressures are presented. The mixtures were produced by mechanical milling and handled under welding-grade argon. The dehydrogenation reactions were studied by means of temperature programmed desorption (TPD) at 400 °C and at 3 or 5 bar initial hydrogen pressure. The milled and dehydrogenated materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transformed infrared spectroscopy (FT-IR) The additives and the surface oxidation, promoted by the impurities in the welding-grade argon, induced a reduction in the dehydrogenation temperature and an increase in the reaction kinetics, as compared to pure (reported) LiBH4. The dehydrogenation reactions were observed to take place in two main steps, with onsets at 100 °C and 200–300 °C. The maximum released hydrogen was 9.3 wt % in the 2LiBH4 + Al/TiF3 material, and 7.9 wt % in the 2LiBH4 + Al/CeO2 material. Formation of CeB6 after dehydrogenation of 2LiBH4 + Al/CeO2 was confirmed.
Highlights
LiBH4 is an outstanding material regarding its hydrogen content (18.4 wt %) [1]
To reduce the dehydrogenation temperature, improve reaction kinetics or reversibility, LiBH4 has been mixed with several compounds in different proportions
The loss of available B for the re-hydrogenation reaction is a common and 2LiBH4 + Al/CeO2 materials dehydrogenated at 5 bar, other scanning electron microscopy (SEM) images are available in the drawback for all borohydrides and their mixtures
Summary
LiBH4 is an outstanding material regarding its hydrogen content (18.4 wt %) [1]. its dehydrogenation temperature is too high for any practical application in hydrogen storage. LiBH4 + Al (1:0.5) was characterized by in-situ synchrotron radiation powder X-ray diffraction from room temperature to 500 ◦ C and dynamic vacuum [21] Among the additives for improving reaction kinetics or reversibility; TiF3 is the material most commonly used, and it is almost mandatory to test TiF3 in all new mixtures. In their part, oxides such as TiO2 , ZrO2 , Nb2 O5 or MoO3 have resulted in successful accelerators for hydrogen desorption reactions [23,24].
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