Ames Laboratory; Chemistry; Materials Science and Engineering; Physics and Astronomy
Ames Laboratory, Chemistry, Materials Science and Engineering, Physics and Astronomy
International Journal of Hydrogen Energy
The hydrogen storage properties, and phase compositions of mechanochemically prepared mixtures of xMBH4-SiS2 (x = 2–8), where M = Li or Na, were investigated using gas sorption analysis, powder X-ray diffraction, and infrared and solid-state NMR spectroscopic methods. The 2LiBH4:1SiS2 system forms an amorphous product that releases ca. 4.3 wt % of H2 below 385 °C with a Tonset of 88 °C without detectable diborane emission. The dehydrogenated sample reversibly absorbs 1.5 wt % of H2 at 385 °C under 160 bar pressure. The H2 release from materials with varying LiBH4:SiS2 ratios peaks at 8.2 wt % for the 6LiBH4:1SiS2 composition, with a reversible hydrogen storage capacity of 2.4 wt %. The H2 desorption capacities of the Li-containing systems surpass those of Na-containing systems. Solid-state NMR studies indicate that products of mechanochemical reactions in the LiBH4SiS2 system consist of one-dimensional chains of edge-sharing SiS4/2 tetrahedra in which the non-bridging S-ends are terminated with Li+, which are further coordinated to the [BH4]− anions. A variety of possible polymorphs in the LiSiS-(BH4) composition space have been identified using first principles and thermodynamic modeling that supports the likelihood of formation of such novel complexes.
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Iowa State University Digital Repository, Ames IA (United States)