LiBH4/SBA-15 Nanocomposites Prepared by Melt Infiltration under Hydrogen Pressure: Synthesis and Hydrogen Sorption Properties

Abstract

Lithium borohydride (LiBH4) is a promising material for hydrogen storage, with a gravimetric hydrogen content of 18.5%. However, the thermodynamics and kinetics of its hydrogen release and uptake need to be improved before it can meet the requirements for mobile applications. In this study, we investigate the confinement of LiBH4 in ordered mesoporous SiO2 and its effect on the hydrogen sorption properties. We demonstrate that, only under hydrogen pressure, melt infiltration is an effective method for the synthesis of LiBH4/SBA-15 nanocomposites. Our work clearly shows that formation of lithium silicates from LiBH4 and SiO2 can effectively be suppressed by hydrogen. Thus, under hydrogen pressure, LiBH4 can fully fill the mesopores of SBA-15 while the long-range order of the mesopores is maintained. The confined LiBH4 has enhanced hydrogen desorption properties, with desorption starting at 150 °C. However, upon dehydrogenation, SiO2 and decomposition products of LiBH4 react to form Li2SiO3 and Li4SiO4, leading to irreversible hydrogen loss.