The thermal decomposition of ammonia borane was studied using a variety of methods to qualitatively identify gas and remnant solid phase species after thermal treatments up to 1500 °C. At about 110 °C, ammonia borane begins to decompose yielding H(2) as the major gas phase product. A two step decomposition process leading to a polymeric -[NH═BH](n)- species above 130 °C is generally accepted. In this comprehensive study of decomposition pathways, we confirm the first two decomposition steps and identify a third process initiating at 1170 °C which leads to a semicrystalline hexagonal phase boron nitride. Thermogravimetric analysis (TGA) was used to identify the onset of the third step. Temperature programmed desorption-mass spectroscopy (TPD-MS) and vacuum line methods identify molecular aminoborane (H(2)N═BH(2)) as a species that can be released in appreciable quantities with the other major impurity, borazine. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to identify the chemical states present in the solid phase material after each stage of decomposition. The boron nitride product was examined for composition, structure, and morphology using scanning Auger microscopy (SAM), powder X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). Thermogravimetric Analysis-Mass Spectroscopy (TGA-MS) and Differential Scanning Calorimetry (DSC) were used to identify the onset temperature of the first two mass loss events.

Cationic contamination is known to cause performance degradation and reduced lifetime in polymer electrolyte based electrochemical systems. Calcium is an important cationic impurity due to its prevalence in roadside particulates and as an airborne contaminant. The role of calcium ion (Ca 2+ ) is investigated in-situ by injecting a solution of calcium sulfate (CaSO 4 ) in deionized (DI) water into the cathode of a polymer electrolyte membrane (PEM) fuel cell through a nebulizer. Stability tests are conducted to determine the effects at various current densities with various Ca 2+ concentrations. It is found that 5 parts per million (ppm, molar ratio) eq. Ca 2+ in air is sufficient to lead to high cell performance loss at 1 A/cm 2 as well as severe membrane degradation. Precipitation of CaSO 4 is found at the contact regions between the gas diffusion layers (GDL) and bipolar plates of the cathode at all test conditions. The amount of precipitation becomes sufficient to cause mass transport issues.

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