THE STABILITY AND REVERSIBILITY OF METALLIC BOROHYDRIDES
In effort to develop reversible metallic borohydrides with high hydrogen storage capacity and low dehydriding temperature, several new materials have been synthesized by modifying LiBH{sub 4} with various metal halides and hydrides. The investigation shows that the halide modification effectively reduced the dehydriding temperature through ion exchange interaction. The effective halides are TiCl{sub 3}, TiF{sub 3}, ZnF{sub 2} and AlF{sub 3}. The material LiBH{sub 4}+0.1TiF{sub 3} desorbs 3.5wt% and 8.5wt% hydrogen at 150 C and 450 C respectively. It re-absorbed 6wt% hydrogen at 500 C and 70 bar after dehydrogenation. The XRD of the rehydrided samples confirmed the formation of LiBH{sub 4}. It indicates that the materials are reversible at the conditions given. However, a number of other halides: MgF{sub 2}, MgCl{sub 2}, CaCl{sub 2}, SrCl{sub 2} and FeCl{sub 3}, did not reduce dehydriding temperature of LiBH{sub 4} significantly. TGA-RGA analysis indicated that some halide modified lithium borohydrides such as LiBH{sub 4}+0.1ZnF{sub 2} evolved diborane during dehydrogenation, but some did not such as LiBH{sub 4}+0.1TiCl{sub 3}. The formation of diborane caused unrecoverable capacity loss resulting in irreversibility. It is suggested that the lithium borohydrides modified by the halides containing the metals that can not form metal borides with boron are likely to evolve diborane during dehydriding. It was discovered that halide modification reduces sensitivity of LiBH{sub 4}. The materials such as LiBH{sub 4}+0.1TiCl{sub 3} and LiBH{sub 4}+0.5TiCl{sub 3} can be handled in open air without visible reaction.
- Research Organization:
- SRS
- Sponsoring Organization:
- DOE
- DOE Contract Number:
- AC09-96SR18500
- OSTI ID:
- 910466
- Report Number(s):
- WSRC-STI-2007-00321
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry; ISSN JPCHAX; ISSN 0022-3654
- Publisher:
- pubinfo
- Country of Publication:
- United States
- Language:
- English
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