Chemical Hydrogen Storage Using Polyhedral Borane Anions and Aluminum-Ammonia-Borane Complexes

Abstract

Executive SummaryThis project was part of the DOE Center of Excellence for chemical hydrogen storage led by the Los Alamos National Laboratory. The project was initiated at UCLA in 2005 and later moved to the University of Missouri in 2006 due to the transfer of the PI to Missouri. This program was divided into two phases; phase 1 was focused on development of transition metal-catalyzed hydrolysis of polyhedral borane anions, specifically nido-B 11 H 14 -, closo-B 10 H 10 2-and closo-B 12 H 12 2-to release hydrogen, while phase 2 was focused on the synthesis and dehydrogenation of aluminum amido-boranes.

Mono- and Bimetalic Amidoboranes

“…11 B NMR spectra of these salts contain a single characteristic signal at ca.´21 ppm (similar to that seen for the parent ammonia borane [18,23,35] On the other hand, the 11 B MAS NMR measurements for the samples in the solid state give one broad peak at about´21 ppm [18,25,29,[38][39][40]43,45]. In Figure 4, we have shown a collection of the 11 B NMR spectra, while, in Table 3, we have listed 11 B NMR chemical shifts and J-coupling constants for various amidoboranes present studied so far.…”

“…On the other hand, several other groups reported for these materials the desorption of hydrogen contaminated with ammonia: α-LiAB [20,25,39,89,90], β-LiAB [20] and NaAB [23,24,87,88,98]. Some amidoborane salts (KAB [25,89], Mg(AB) 2 [29], Al(AB) 3 [35], and LiAl(AB) 4 [35,40]) were reported to desorb pure hydrogen and, currently, there are no contradictory reports. The remaining known amidoborane compounds (RbAB [26], CsAB [26], Sr(AB) 2 [43], Y(AB) 3 [38], LiNa(AB) 2 [39], NaAl(AB) 4 [41], NaMg(AB) 3 [42], Na 2 Mg(AB) 4 [44]) decompose releasing hydrogen contaminated with ammonia, diborane or borazine, all of which are harmful for PEM and alkaline fuel cells.…”

“…Zn(AB) 2 was not investigated with the powder X-ray diffraction due to its high sensitivity to manual grinding (as required for loading of a capillary for an X-ray measurement). 3 and found a methatetic approach to be the most efficient [35,36]. Al(AB) 3 can be obtained from light alkali metal amidoboranes (LiAB, NaAB, KAB) and AlCl 3 at low temperature according to Equation (21) [35,36].…”

“…3 and found a methatetic approach to be the most efficient [35,36]. Al(AB) 3 can be obtained from light alkali metal amidoboranes (LiAB, NaAB, KAB) and AlCl 3 at low temperature according to Equation (21) [35,36]. The product contain mixture of Al(AB) 3 and MCl "dead mass" which cannot be removed from the post-reaction mixture.…”

“…Al(AB) 3 is a crystalline solid material which gives a characteristic X-ray powder pattern [35]. Crystal structure of Al(AB) 3 has not yet been reported.…”