Hydrazine borane: synthesis, characterization, and application prospects in chemical hydrogen storage

Abstract

Hydrazine borane (N₂H₄BH₃) is the novel boron- and nitrogen-based material appearing to be a promising candidate in chemical hydrogen storage. It stores 15.4 wt% of hydrogen in hydridic and protic forms, and the challenge is to release H₂ with maximum efficiency, if possible all hydrogen stored in the material. An important step to realize this ambitious goal is to synthesize HB with high yields and high purity, and to characterize it fully. In this work, we report a 2-step synthesis (salt metathesis and solvent extraction-drying) through which N₂H₄BH₃ is successfully obtained in 3 days, with a yield of about 80% and a purity of 99.6%. N₂H₄BH₃ was characterized by NMR, IR, XRD, TGA and DSC, its stability in dioxane and water was determined, and its thermolysis by-products were characterized. We thus present a complete data sheet that should be very useful for future studies. Furthermore, we propose a discussion on the potential of HB (with H₂ released by either thermolysis or hydrolysis) in chemical hydrogen storage.