Borohydride-induced destabilization of hydrazine borane

We investigated the destabilization of 4 mol of hydrazine borane N2H4BH3 in the presence of 1 mol of an alkaline borohydride (LiBH4 or NaBH4) and, in a second step, of 1 mol of NH3BH3 in addition. The destabilization was followed by TGA, DSC and μGC. The solid residues were analyzed by solid-state 11B NMR, IR and XRD. The presence of the borohydride effectively destabilizes N2H4BH3 which is thus able to liberate H2 from 50 °C. Seeing the results from the other side, one could consider that the alkaline borohydrides are destabilized by N2H4BH3. Such destabilization approach is attractive as it involves boron-based materials only. The best decomposition results were obtained with the sample containing 4 mol of N2H4BH3 and 1 mol of LiBH4 (containing 16 equiv. H2). Upon heating up to 300 °C at 5 °C min−1, this sample releases 12.1 mol of H2 (dehydrogenation extent of 76%) and 1.1 mol of N2H4. A solid residue of empirical formulae LiB5N5.8H3.4 is formed. It is composed of polyborazylene- and/or boron nitride-like materials. This is an attractive feature as it implies recyclability of the polymer and elaboration of inorganic ceramics at relatively low temperatures. Our main results are reported herein.