Development of metal borohydrides for hydrogen storage

• Published in: The Journal of physics and chemistry of solids Vol. 69; no. 9; pp. 2292 - 2296
• Main Authors: Nakamori, Y., Li, H.-W., Matsuo, M., Miwa, K., Towata, S., Orimo, S.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 01.09.2008; Elsevier
• Subjects: A. Inorganic compounds; Alternative fuels. Production and utilization; Applied sciences; D. Thermodynamic properties; Energy; Exact sciences and technology; Fuels; Hydrogen; A. Inorganic compounds; D. Thermodynamic properties; Metal Hydroborates; Hydrogen storage; TDS; Enthalpy; Microwave; Thermodynamic stability; Desorption; Electronegativity; Mechanical alloying; Thermal properties; Hydrogen storage material; Kinetics
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/j.jpcs.2008.04.017

A metal borohydride M(BH 4) n is a potential candidate for hydrogen storage materials because of its high gravimetric hydrogen density. The important research issues for M(BH 4) n are to control the thermodynamic stability and to achieve the faster reaction kinetics. To clarify the thermodynamic stability, M(BH 4) n ( M=Mg, Ca∼Mn, Zn, Al, Y, Zr and Hf; n=2–4) were synthesized by mechanical milling and its thermal desorption properties were investigated. The hydrogen desorption temperature T d of M(BH 4) n decreases with increasing Pauling's electronegativities χ P of M. Because Mn, Zn, and Al borohydrides ( χ P⩾1.5) desorb borane, they are too unstable for hydrogen storage applications. The enthalpy changes of desorption reaction Δ H des can be estimated by using our predicted heat of formation of M(BH 4) n Δ H boro and reported data for decomposed products Δ H prod, which are useful indicators for searching M(BH 4) n with appropriate stability for hydrogen storage material. In the latter case, microwave processing was adopted for achieving fast reaction kinetics. Among metal borohydrides, LiBH 4 was rapidly heated above 380 K by microwave irradiation, 13.7 mass% of hydrogen was desorbed by microwave irradiation. The composites of LiBH 4 with B or C desorbed hydrogen within 3 min. Microwave heating aids in realizing faster kinetics of the hydrogen desorption reaction.