Effect of milling and doping on decomposition of NH3BH3 complex

The thermal decomposition of borane-ammonia complex as well as of milled and doped samples was studied by volumetric titrations. The samples were heated at fixed temperature and the volume of the evolved gas recorded as a function of time. Milled and doped samples were prepared by mechanical and mechanochemical reactions, respectively. Samples containing I and 2 mol% hydrogen hexachloroplatinate hydrate were prepared. The materials were characterized by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). Mechanical alloying was effective to modify the crystallinity of the complex and to change the material morphology enhancing the amount of gas evolved. Both the milled and the doped samples showed an increase of the pre-exponential factor in the Arrhenius equation. The activation energy decreased for the doped sample, and it increased for the milled sample. As a result it was found that the decomposition of I mol% doped sample could be provided by waste heat coming from polymer electrolyte membrane fuel cell. (C) 2005 Elsevier B.V All rights reserved.