Publication Date

2-1-2018

Department

Ames Laboratory; Materials Science and Engineering; Chemistry

Campus Units

Ames Laboratory, Materials Science and Engineering, Chemistry

Report Number

IS-J 9595

DOI

10.1021/acs.jpcc.7b10856

Journal Title

Journal of Physical Chemistry C

Volume Number

122

Issue Number

4

First Page

1955

Last Page

1962

Abstract

The double-cation metal borohydride, Li4Al3(BH4)(13), mechanochemically produced from a 13:3 mixture of lithium borohydride (LiBH4) and aluminum chloride (AlCl3), has a low hydrogen desorption temperature; however, the material's decomposition is accompanied by a large emission of toxic diborane (B2H6). We found that a decrease of the LiBH4:AICl(3) ratio in the starting mixture yields increased amounts of partially chlorinated products that also dehydrogenate at low temperature, but release negligibly small amounts of diborane. Extensive characterization by solid-state NMR spectroscopy (SSNMR) and powder X-ray diffraction (XRD) found that the 11:3 ratio product maintains the Li(4)A(13)(BH4)(13)-like structure, with additional anions substituting for [BH4](-) compared to the 13:3 mixture. Further decrease of relative LiBH4 concentration in the starting mixture to 9:3 results in a different product composed of tetrahedral [Al(BH4)(4)](-) and [Al(BH4)(2)Cl-2](-) complexes, in which two hydrogen atoms of each borohydride group are bridged to aluminum sites. Additionally, SSNMR revealed the covalent character of the Al-H bonds, which is not observed in Li(4)A(13)(BH4)(13). These findings suggest that the Al-Cl bonding present in the chlorinated complexes prevents the formation of Al(BH4)(3), which is a known intermediate leading to the formation of diborane during thermal dehydrogenation of the nearly chlorine-free Li(4)A(13)(BH4)(13).

DOE Contract Number(s)

EE-0007047; AC02-07CH11358

Language

en

Department of Energy Subject Categories

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY

Publisher

Iowa State University Digital Repository, Ames IA (United States)

Available for download on Wednesday, December 19, 2018

Share

COinS