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

Lithium borohydride (LiBH 4 ) 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 LiBH 4 in ordered mesoporous SiO 2 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 LiBH 4 /SBA-15 nanocomposites. Our work clearly shows that formation of lithium silicates from LiBH 4 and SiO 2 can effectively be suppressed by hydrogen. Thus, under hydrogen pressure, LiBH 4 can fully fill the mesopores of SBA-15 while the long-range order of the mesopores is maintained. The confined LiBH 4 has enhanced hydrogen desorption properties, with desorption starting at 150 °C. However, upon dehydrogenation, SiO 2 and decomposition products of LiBH 4 react to form Li 2 SiO 3 and Li 4 SiO 4, leading to irreversible hydrogen loss.