Novel synthesis of porous aluminium and its application in hydrogen storage

Abstract

A novel approach for confining LiBH4 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 NaAlH4, which was in the form of a dense pellet, under dynamic vacuum. The final product was a porous aluminium scaffold with the Na and H2 having been removed from the initial pellet. This technique contributed to achieving highly dispersed LiBH4 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 LiBH4 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 LiBH4 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 (Tdes) of the LiBH4 infiltrated into the porous aluminium scaffold was 200 °C lower than that of bulk LiBH4 and 100 °C lower than that of nanosized LiBH4. Partial cycling could be achieved below the melting point of LiBH4 but the kinetics of hydrogen release decreased with cycle number.