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Probing the structure, stability and hydrogen storage properties of calcium dodecahydro-closo-dodecaborate |
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| Authors: | Vitalie Stavila Jae-Hyuk Her Wei Zhou Son-Jong Hwang Leigh Anna M Ottley |
| Institution: | a Sandia National Laboratories, Livermore, CA 94551, United States b Sandia National Laboratories, Albuquerque, NM 87106, United States c NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, United States d Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, United States e Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, United States |
| Abstract: | Calcium borohydride can reversibly store up to 9.6 wt% hydrogen; however, the material displays poor cyclability, generally associated with the formation of stable intermediate species. In an effort to understand the role of such intermediates on the hydrogen storage properties of Ca(BH4)2, calcium dodecahydro-closo-dodecaborate was isolated and characterized by diffraction and spectroscopic techniques. The crystal structure of CaB12H12 was determined from powder XRD data and confirmed by DFT and neutron vibrational spectroscopy studies. Attempts to dehydrogenate/hydrogenate mixtures of CaB12H12 and CaH2 were made under conditions known to favor partial reversibility in calcium borohydride. However, up to 670 K no notable formation of Ca(BH4)2 (during hydrogenation) or CaB6 (during dehydrogenation) occurred. It was demonstrated that the stability of CaB12H12 can be significantly altered using CaH2 as a destabilizing agent to favor the hydrogen release. |
| Keywords: | Calcium dodedecahydro-closo-dodecaborate Hydrogen storage Metal borohydrides X-ray and neutron techniques Density functional theory |
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