Silane-based hydrogen storage materials for fuel cell application: Hydrogen release via methanolysis and regeneration by hydride reduction from organosilanes

A series of cyclic- and linear organosilanes, 1-5, was prepared and examined as potential hydrogen storage materials. When a stoichiometric amount of methanol was added to a mixture of cyclic organosilane, (CH ₂SiH₂)₃ (1) or (CH₂SiH ₂CHSiH₃)₂ (2), and 5 mol% NaOMe, rapid hydrogen release was observed at room temperature within 10-15 s. The hydrogen storage capacities of compounds 1 and 2 were estimated to be 3.70 and 4.04 wt.-% H ₂, respectively. However, to ensure the complete methanolysis from organosilanes including methanol evaporation at exothermic dehydrogenation condition, two equivs of methanol were used. The resulting methoxysilanes, (CH₂Si(OMe)₂)₃ (6) and (CH₂Si(OMe) ₂CHSi(OMe)₃)₂ (7), were regenerated to the starting organosilanes in high yields by LiAlH₄ reduction. Linear organosilanes, SiH₃CH₂SiH₂CH ₂SiH₃ (3), SiH₃CH₂CH(SiH ₃)₂ (4), and SiH₃CH₂CH(SiH ₃)CH₂SiH₃ (5) also showed fast hydrogen release kinetics at room temperature with hydrogen storage capacities of 4.26, 4.55, and 4.27 wt.% H₂, respectively; the corresponding methoxysilanes were successfully regenerated by LiAlH₄. Compound 1 was further tested as hydrogen source for fuel cell operation.