Ammonia borane with polyvinylpyrrolidone as a hydrogen storage material: Comparison of different molecular weights

We report thermal and infrared transmission measurements on ammonia borane (NH3BH3, AB), and its bulk composites with polyvinylpyrrolidone (PVP) as a function of temperature. X-ray studies reveal an amorphous phase combined the AB crystalline with the addition of the polymer. We determine the activation energies in the temperature range from 25 degrees C to 300 degrees C with various ramp rates via kinetic studies. These activation energies of AB:PVP bulk composites were found to be lower than the pristine AB. Overall, the composites with higher molecular weight and high polymer content revealed the greatest decrease in Ea. The weight loss provided similar results, it decreased from 57.8% for AB to 10.5% for the polymer composite. The FT-IR studies of AB and the bulk composites showed evidence of the interaction between the boron atom of AB and the oxygen atom of the carbonyl group in PVP. An explanation of the hydrogen release pattern during decomposition at higher temperatures ranging from 25 degrees C to 300 degrees C is also provided.