Understanding and Mitigating the Effects of Stable Dodecahydro-closo-dodecaborate Intermediates on Hydrogen Storage Reactions

Published

October 25, 2016

Author(s)

James L. White, Rebecca J. Newhouse, Jin Z. Zhang, Terrence J. Udovic, Vitalie Stavila

Abstract

Alkali metal borohydrides can reversibly store hydrogen; however, the materials display poor cyclability, often times linked to occurrence of stable closo-polyborate intermediate species. In an effort to understand the role of such intermediates on the hydrogen storage properties of metal borohydrides, several alkali metal dodecahydro-closo-dodecaborate salts were isolated in anhydrous form and characterized by diffraction and spectroscopic techniques. Mixtures of Li₂B₁₂H₁₂, Na₂B₁₂H₁₂, and K₂B₁₂H₁₂ with the corresponding alkali metal hydrides were subjected to hydrogenation conditions known to favor partial or full reversibility in metal borohydrides. The stoichiometric mixtures of MH and M₂B₁₂H₁₂ salts form the corresponding metal borohydrides MBH₄ (M=Li, Na, K) in almost quantitative yield at 100 MPa H₂ and 500 °C. In addition, stoichiometric mixtures of Li₂B₁₂H₁₂ and MgH₂ were found to form MgB₂ at 500 °C and above upon desorption in vacuum. The two destabilization strategies outlined above suggest that metal polyhydro-closo-polyborate species can be converted into the corresponding metal borohydrides or borides, albeit under rather harsh conditions of hydrogen pressure and temperature.

Citation

Journal of Physical Chemistry C

Volume

120

Pub Type

Journals

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Keywords

borohydrides, dodecahydro-closo-dodecaborates, hydrogenation, hydrogen-storage materials, intermediates, neutron vibrational spectroscopy, nuclear magnetic resonance, Raman spectroscopy, x-ray diffraction

Citation

White, J. , Newhouse, R. , Zhang, J. , Udovic, T. and Stavila, V. (2016), Understanding and Mitigating the Effects of Stable Dodecahydro-closo-dodecaborate Intermediates on Hydrogen Storage Reactions, Journal of Physical Chemistry C, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=921709 (Accessed October 15, 2024)