Ammonia borane (NH3BH3, AB) has a lot of prospect for solid state hydrogen storage because it readily decomposes around 110 °C giving one mole of hydrogen. Even though AB has high gravimetric hydrogen density, the practical use as a fuel is limited due to high dehydrogenation temperature, slow kinetics, long incubation time, production of impurities and unwanted gases. Lots of studies were conducted after modifying AB with different functional materials such as polymers, catalysts, and metal organic frameworks (MOF). In current study, we used polyethylene oxide (PEO) to make new functional bulk composites of AB. A catalyst (MgCl2) was also added for further modification. To understand the dehydrogenation mechanism of AB and its polymer composites in solid state, we utilized thermal and spectroscopic methods. The findings from all data indicated that the polymeric composites possibly involve the breakdown of dative bond and initiate a new interaction (H-bonding) between AB and the polymer. The higher the PEO mass ratio the more pronounced the interaction was. The activation energies were calculated from the heat flow measurements using Differential Scanning Calorimeter (DSC) with several different ramp rates. It was found lower for the polymeric composites than the pristine AB showing the enhanced kinetics. Dehydrogenation properties were also evaluated by DSC. 15N and 11B solid- state Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) spectroscopy at room temperature were performed to understand the interaction between AB and PEO which is explained by possible H-bonding. 11B MAS-NMR experiments at 85 °C were also conducted to investigate the isothermal decomposition during several hours. Spectra indicated that pristine AB takes longer incubation time, however the polymeric composite readily decomposes at 85 °C. Furthermore, IR studies supported the interaction between AB and the polymer. All of these results indicated that the improved properties of dehydrogenation including better kinetics which is probably due the interaction between AB and PEO. These findings would also facilitate the understanding and developing possible other novel functional materials as a candidate for hydrogen storage.

Properties of bulk ammonia borane – polyethylene oxide hydrogen storage composites via thermal and spectroscopic (IR, NMR) techniques

2019 Spring National Meeting

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