Metastability and Crystal Structure of the Bialkali Complex Metal Hydride NaK(BH4)2.

Seballos, L. ; Zhang, J. Z. ; Ronnebro, E. ; Herberg, J. L. ; Majzoub, E. H.

Technical Information Center Oak Ridge Tennessee

关键词: Metastability;    Crystal structure;    Mechanical milling;    Hydrogen storage;    Stability;   

RP-ID  :  PB2012105271

学科分类：工程和技术（综合）

美国|英语

来源: National Technical Reports Library

【 摘 要 】

A new bialkali borohydride, NaK(BH4)2, was synthesized by mechanical milling of NaBH4 and KBH4 in a 1:1 ratio. The synthesis was conducted based on a prediction from a computational screening of hydrogen storage materials suggesting the potential stability of NaK(BH4)2. The new phase was characterized using X-ray diffraction, Raman scattering and magic angle spinning (MAS) nuclear magnetic resonance (NMR). The Raman measurements indicated B-H vibrations of the (BH4)- anion, while magnetic resonance chemical shifts in 23Na, and 39K MAS NMR spectra showed new chemical environments for Na and K resulting from the formation of the new bialkali phase. X-ray diffraction spectra indicated a new crystal structure with rhombohedral symmetry, most likely in the space group R3, distinct from the starting materials NaBH4, and KBH4. Although in-situ XRD measurements indicated the material to be metastable, decomposing to the starting materials NaBH4 and KBH4, the successful synthesis of NaK(BH4)2 demonstrates the ability of computational screening to predict candidates for hydrogen storage materials.