Abstract:Research for suitable hydrogen storage materials is an important ongoing subject. LiBH 4 -Al mixtures could be attractive; however, several issues must be solved. Here, the dehydrogenation reactions of surface-oxidized 2LiBH 4 + Al mixtures plus an additive (TiF 3 or CeO 2 ) 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) LiBH 4 . 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 2LiBH 4 + Al/TiF 3 material, and 7.9 wt % in the 2LiBH 4 + Al/CeO 2 material. Formation of CeB 6 after dehydrogenation of 2LiBH 4 + Al/CeO 2 was confirmed.
The hydrogenation of NaF/9NaH + 5MgB 2 and NaF/ 2NaH + 1.5MgB 2 reactive hydride composites (RHC) was studied by volumetric titration (kinetics and PCI curves), in situ synchrotron radiation powder X-ray diffraction (SR-PXD), high-pressure differential scanning calorimetry (HP-DSC), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM). A hydrogen uptake between 4.1 and 4.8 wt % was observed when the H 2 pressure was in the range between 25 and 50 bar, and the temperature was kept constant at 325 °C. PCI curves indicate a hydrogenation equilibrium pressure of 2 and 8 bar at 325 °C for NaF/9NaH + 5MgB 2 and NaF/ 2NaH + 1.5MgB 2 , respectively. Synchrotron radiation powder X-ray diffraction revealed the formation of solid solutions of NaF−NaH after milling and a change in the reaction pathway compared to a reported nondoped 2NaH + MgB 2 reactive hydride composite. Formation of the stable side-product NaMgH 2 F was found as a drawback for hydrogen storage capacity and reversibility. FT-IR indicates no hydrogen to fluorine substitution in the NaBH 4 product.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.