B NMR spectroscopy has been employed to identify the reaction intermediates and products formed in the amorphous phase during the thermal hydrogen desorption of metal tetrahydroborates (borohydrides) LiBH 4 , Mg(BH 4 ) 2 , LiSc(BH 4 ) 4 , and the mixed Ca(AlH 4 ) 2 -LiBH 4 system. The 11 B magic angle spinning (MAS) and cross polarization magic angle spinning (CPMAS) spectral features of the amorphous intermediate species closely coincide with those of a model compound, closo-borane K 2 B 12 H 12 that contains the [B 12 H 12 ] 2anion. The presence of [B 12 H 12 ] 2in the partially decomposed borohydrides was further confirmed by high-resolution solution 11 B and 1 H NMR spectra after dissolution of the intermediate desorption powders in water. The formation of the closo-borane structure is observed as a major intermediate species in all of the metal borohydride systems we have examined.

Beyond hydrogen storage: The first example of reversible magnesium deposition/stripping onto/from an inorganic salt was seen for a magnesium borohydride electrolyte. High coulombic efficiency of up to 94 % was achieved in dimethoxyethane solvent. This Mg(BH4)2 electrolyte was utilized in a rechargeable magnesium battery.