Regeneration of Ammonia Borane Spent Fuel by Direct Reaction with Hydrazine and Liquid Ammonia

Ammonia borane (H3N-BH3, AB) is a lightweight material containing a high density of hydrogen (H-2) that can be readily liberated for use in fuel cell-powered applications. However, in the absence of a straightforward, efficient method for regenerating AB from dehydrogenated polymeric spent fuel, its full potential as a viable H-2 storage material will not be realized. We demonstrate that the spent fuel type derived from the removal of greater than two equivalents of H-2 per molecule of AB (i.e., polyborazylene, PB) can be converted back to AB nearly quantitatively by 24-hour treatment with hydrazine (N2H4) in liquid ammonia (NH3) at 40 degrees C in a sealed pressure vessel.