Syntheses and Hydrogen Desorption Properties of Metal-Borohydrides M(BH₄)_n (M=Mg, Sc, Zr, Ti, and Zn; n=2–4) as Advanced Hydrogen Storage Materials

抄録

Metal-borohydrides M(BH₄)_n (M=Mg, Sc, Zr, Ti, and Zn; n=2–4) were synthesized by mechanical milling process according to the following reaction; MCl_n+nLiBH₄/nNaBH₄→M(BH₄)_n+nLiCl/nNaCl. Then the thermal desorption properties of M(BH₄)_n were investigated by gas-chromatography and mass-spectroscopy combined with thermogravimetry. The results indicate that the hydrogen desorption temperature T_d of M(BH₄)_n correlates with the Pauling electronegativity χ_P of M; that is, T_d decreases with increasing value of χ_P. The components of desorbed gas for M=Mg, Sc, Zr and Ti (χ_P≤1.5) are hydrogen only, while that for M=Zn (χ_P=1.6) contains borane besides hydrogen. The Pauling electronegativity χ_P of M is an indicator to estimate T_d of M(BH₄)_n as candidates for advanced hydrogen storage materials with high gravimetric hydrogen densities and low desorption temperatures.