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

Abstract

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 2SiH 2) 3 ( 1) or (CH 2SiH 2CHSiH 3) 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, (CH 2Si(OMe) 2) 3 ( 6) and (CH 2Si(OMe) 2CHSi(OMe) 3) 2 ( 7), were regenerated to the starting organosilanes in high yields by LiAlH 4 reduction. Linear organosilanes, SiH 3CH 2SiH 2CH 2SiH 3 ( 3), SiH 3CH 2CH(SiH 3) 2 ( 4), and SiH 3CH 2CH(SiH 3)CH 2SiH 3 ( 5) also showed fast hydrogen release kinetics at room temperature with hydrogen storage capacities of 4.26, 4.55, and 4.27 wt.% H 2, respectively; the corresponding methoxysilanes were successfully regenerated by LiAlH 4. Compound 1 was further tested as hydrogen source for fuel cell operation.