Catalytic Cleavage of the Dative Bond of Ammonia Borane by Polymeric Carbonyl Groups for Enhanced Energy Generation

Abstract

Dissociation of the dative (B–N) bond of ammonia borane (NH3BH3/AB) is essential to prevent its thermochemical oligomerization to chemically resistant BNHx compounds, for its applicability as a fuel in high-energy propulsion systems. We show that when AB is incorporated into polymer matrices containing carbonyl functional groups, thermal activation causes the carbonyl groups to engage in nucleophilic interactions with AB. Such interactions catalyze the lysis of the dative B–N bond resulting in the decomposition of AB to NH3 and B2H6 gases, with no evidence of oligomerization. We find that the carbonyl groups function as catalysts and do not participate in any net reaction. In situ high-heating rate (∼105 K/s) characterizations demonstrate that facile-synthesized hierarchical (micro/nano) composite particles of AB/carbonyl-based polymers completely gasify to NH3 and B2H6 at ∼510 K, followed by spontaneous ignition in the air with negligible delay. Thus, the current chemical pathway enables the solid-state storage of reactive fuels, NH3 and B2H6, and their controlled on-demand release for high-energy applications.