Transmission IR Studies of Hydrogen Storage Materials Michael Trenary, Department of Chemistry, University of Illinois at Chicago Borohydrides such as NaBH4 and LiBH4 are attractive as hydrogen storage materials because of their high weight percentages of hydrogen. However, it has been observed that the amount of hydrogen released from the thermal decomposition of borohydrides is less than expected and it has been hypothesized that this is because stable intermediates form. The following reaction sequence has been proposed involving formation of a stable B12H122- anion.
NaBH4 Æ 1/12Na2B12H12 + 5/6NaH + 13/12H2 1/12Na2B12H12 Æ NaH + B + 3/2H2 To determine if this reaction occurs, IR spectra were obtained for salts containing the BH4- and B12H122- anions as a function of temperature. Spectra obtained at room temperature are shown below. 2293
1126 Absorbance
2225
IR spectrum of KBH4 at 300 K
BH4-
2388
1442
1000
1500
3272
2000 2500 Wavenumber (cm-1)
3000
3500
B12H12-2
Absorbance
IR spectrum of K2B12H12 at 298 K
2485
1076
1000
1500
2000 2500 Wavenumber (cm-1)
3000
3500
