Catalytic Dehydrogenation of Ammonia Borane-Polyvinylpyrrolidone Hydrogen Storage Composites with Different Molecular Weight

Ammonia borane (NH3BH3, AB) is a promising hydrogen storage material to be used in hydrogen fuel cells, but its application is restricted by the slow hydrogen release and unwanted byproducts. The bulk composites were prepared by mixing AB with polyvinylpyrrolidone (PVP) of different molecular weights in different proportions under vacuum. The catalyst, MgCl 2 was also added to evaluate the changes. High temperature thermal studies via differential scanning calorimeter were performed to investigate dehydrogenation kinetics of the composites with and without the catalyst then compared with pristine AB. We conducted decomposition at several heating rates and calculated activation energies. The activation energies of the composites with MgCl 2 were lower than the neat NH3BH3 as well as the polymer composites. The decrease in the temperature for the release of hydrogen demonstrated the enhanced kinetics for the composites with MgCl2. Thermogravimetric studies were also conducted to bulk composites and AB to know the percentage of weight loss. The percentage weight loss of composites were significantly lower than the pristine AB. FT-IR studies were also performed to bulk composites and AB, which showed the evidence of interaction of polymeric functional group with AB, and the complex formation between N atom in AB with MgCl2. That complex sample could be responsible for the decrease in the ammonia formation during dehydrogenation of AB. All of these results supported the improvement of the kinetic properties of ammonia borane-polyvinylpyrrolidone composites with higher molecular weight content of PVP and addition of MgCl 2 catalyst.