Micro-solid oxide fuel cells running on reformed butane and their functional layers
Dr Barbara Scherrer (University of Sydney, ETH Zurich)
ENGINEERING SEMINARDATE: 2013-04-30
TIME: 16:00:00 - 17:00:00
LOCATION: Graduate Teaching Room (Ian Ross Building)
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ABSTRACT:
Low temperature micro-solid oxide fuel cell (micro-SOFC) systems are a new power source for portable electronic devices. We report on the fabrication of a sub-system assembly of the ONEBAT system. The assembly consists of a startup heater and a micro-reformer bonded to a Si chip with 30 integrated micro-SOFC membranes. The self-sustaining sub-system was successfully tested and electrochemically characterized. A functional glass carrier including fluidic channels for gas feed and integrated thick film heaters was bonded with glass frit to a microreformer with an overall size of 18 x 16 x 2 mm3. A foam-like catalytic bed consisting of rhodium doped ceria-zirconia nanoparticles and SiO2 sand was used to fill the 134.8 mm3 reformer cavity. This reactor allows for high methane and n-butane conversions of > 90 % and high hydrogen selectivity. Thirty free-standing micro-SOFC membranes, each 390 x 390 Am2 with a thickness of less than 500 nm, were integrated on a Si-chip, which was bonded to the carrier-reformer assembly. The micro-SOFC membrane consisted of an yttria-stabilized zirconia thin film electrolyte and porous platinum thin film serving as electrodes. The sub-assembly was electrochemically tested using n-butane as fuel in the temperature range between 300 AC and 600 AC. Pt-based electrodes were tested in the sub-assembly and are compared to nanoporous Pt alloy-based and ceramic-based electrodes regarding thermal stability and carbon poisoning at temperatures below 600 AC. Furthermore, the fuel cell performance and the microstructural evolution of the electrodes are discussed.
In addition I will discuss the processing-microstructure-property relations of nanocrystalline YSZ thin films made by the wet-chemical route of spray pyrolysis. Such YSZ films are thought as electrolyte layers in micro-SOFCs. The microstructural evolution of YSZ thin films during post-deposition heat-treatment and its effect on the microstructure and the electric properties, especially at unusual low temperatures, even down to room temperature.
