We have prepared thin yttria-stabilized zirconia (YSZ) electrolyte layers by chemical vapor deposition (CVD) on a pre-sintered NiO/YSZ fuel cell anode substrate. Structural analysis by scanning electron microscopy (SEM) and x-ray-diffraction shows a homogeneous, nanocrystalline layer.Conventional electrolyte films reach desired electrical properties only at elevated temperatures, typically 1000°C to 1100°C. The YSZ films grown by CVD on rough anode substrates show better growth behavior and less defects at the anode/electrolyte interface than films deposited by conventional methods (screen printing, sol-gel). Results of electrical properties at lower SOFC working temperatures are obtained by impedance spectroscopy on pressed nanocrystalline YSZ powder pellets produced by chemical vapor synthesis (CVS).
The catalytic oxidation of methane was studied over palladium supported on nanocrystalline ceria. Three palladium weight loadings (1, 5, and 10 wt%) were tested after calcining at 500 °C, at 280 °C and after no calcination at all. For the 5 and 10 wt% loadings, the 280 °C-calcined and non-calcined catalysts exhibit enhanced activity after several heating and cooling cycles. Calcining these same catalysts at 500 °C results in a systematic decline in activity. For all pretreatments the 1 wt% Pd catalyst exhibits decreasing activity. For the 5 and 10 wt% Pd loadings, the non-calcined catalysts are more active than the 280 °C-calcined catalysts, which are more active than the 500 °C-calcined catalysts. For the 1 wt% Pd catalyst, the opposite is true. The catalyst activity improves as the Pd loading is increased.
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