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A novel species of metal amidoborane ammoniate, [Al(NH2BH3)63-][Al(NH3)63+] has been successfully synthesized in up to 95% via the one-step reaction of AlH3·OEt2 with liquid NH3BH3·nNH3 (n = 1~6) at 0 °C. This solution based reaction method provides an alternative pathway to the traditional mechano-chemical ball milling methods, avoiding possible decomposition. MAS 27Al NMR spectroscopy confirms the formulation of the compound as an Al(NH2BH3)63- complex anion and an Al(NH3)63+ cation. Initial dehydrogenation studies of this aluminum based M-N-B-H compound demonstrate that hydrogen is released at temperatures as low as 65 °C, totaling ~8.6 equivalents of H2 (10.3 wt %) upon heating to 105 °C. This method of synthesis offers a promising route towards the large scale production of metal amidoborane ammoniate moieties. [ABSTRACT FROM AUTHOR]

Abstract Porous Al scaffolds were synthesised and melt-infiltrated with various eutectic metal borohydride mixtures (0.725LiBH 4 -0.275KBH 4, 0.68NaBH 4 -0.32KBH 4, 0.4NaBH 4 -0.6 Mg(BH 4) 2) to simultaneously act as both a confining framework and a reactive destabilising agent for H 2 release. The scaffolds were synthesised by sintering a pellet of NaAlH 4 /2 mol%TiCl 3 at 450 °C under dynamic vacuum. During the sintering process the sodium alanate (NaAlH 4) decomposed to Al metal. The vacuum applied at elevated temperature promoted the Na metal to vaporise and be extruded from the pellet. The pores of the resulting Al scaffold were created during removal of the H 2 and the Na from the body of the NaAlH 4 /2 mol%TiCl 3 pellet. According to the morphological observations carried out by a Scanning Electron Microscope (SEM), melt-infiltrated eutectic mixtures of metal borohydrides were highly dispersed into the porous scaffolds. Temperature Programmed Desorption (TPD) experiments, revealed that the melt-infiltrated samples exhibited faster H 2 desorption kinetics in comparison to bulk samples, with onset temperatures (T des) lower than the bulk by 150–250 °C. The as-synthesised porous Al scaffolds acted as a reactive containment vessel for these eutectic mixtures that simultaneously nanoconfined and destabilised the mixtures. Highlights • Porous scaffolds were fabricated by sintering a NaAlH 4 /2 mol%TiCl 3 pellet at 450 °C. • The pores formed an open network with thin interconnecting walls. • The porous Al scaffolds destabilised the infiltrated eutectic mixtures. • All melt-infiltrated samples started desorbing H 2 150–250 °C lower than the bulk. • The melt-infiltrated samples showed faster reaction kinetics to the bulk. [ABSTRACT FROM AUTHOR]

A novel approach for confining LiBH 4 within a porous aluminium scaffold was applied in order to enhance its hydrogen storage properties, relative to conventional techniques for confining complex hydrides. The porous aluminium scaffold was fabricated by sintering NaAlH 4, which was in the form of a dense pellet, under dynamic vacuum. The final product was a porous aluminium scaffold with the Na and H 2 having been removed from the initial pellet. This technique contributed to achieving highly dispersed LiBH 4 particles that were also destabilised by the presence of the aluminium scaffold. In this study, the effectiveness of this novel fabrication method of confined/destabilised LiBH 4 was extensively investigated, which aimed to simultaneously improve the hydrogen release at lower temperature and the kinetics of the system. These properties were compared with the properties of other confined LiBH 4 samples found in the literature. As-synthesised samples were characterised using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Nitrogen Adsorption measurements. The hydrogen storage capacity of all samples was analysed using temperature programmed desorption in order to provide a comprehensive survey of their hydrogen desorption properties. The porous aluminium scaffold has a wide pore size distribution with most of the porosity due to pores larger than 50 nm. Despite this the onset hydrogen desorption temperature (T des ) of the LiBH 4 infiltrated into the porous aluminium scaffold was 200 °C lower than that of bulk LiBH 4 and 100 °C lower than that of nanosized LiBH 4 . Partial cycling could be achieved below the melting point of LiBH 4 but the kinetics of hydrogen release decreased with cycle number. [ABSTRACT FROM AUTHOR]