Solid oxide fuel cells (SOFCs) that operate directly on hydrocarbon fuels
eliminate the requirement for costly and complex external reforming systems.
Atmospheric plasma spraying (APS) is an established manufacturing method
that offers the potential to fabricate direct oxidation SOFC anodes in a single
step, instead of the multiple steps currently required. Manufacturing by APS
also allows the use of metal supports, which improve thermal shock resistance,
allow rapid cell heat-up, and reduce total cost. In this study, direct oxidation
SOFC anodes based on Cu and samaria-doped ceria (SDC) in combination with
Co and/or Ni were investigated for their stability and performance in H2 and
CH4 when plasma sprayed on ferritic stainless steel supports. Several different
APS techniques were investigated. Two of these techniques were hybrid methods
involving a combination of dry powder plasma spray and suspension plasma
spray (SPS) processes. These techniques were proposed to help balance the
degree of melting of the lower melting temperature oxides of the metals Cu, Co,
and Ni with that of the higher melting temperature SDC. The use of a single
suspension containing all of the anode component feedstocks was also
investigated. Multi-component aqueous suspensions of CuO, Co3O4, and NiO
were developed with or without the addition of carbon black and SDC. It was
found that the use of a hybrid plasma spray technique can help to improve
deposition efficiency (D.E.) and enhance partial melting of the low melting
temperature feedstocks. However, plasma spraying all of the components in a
single suspension can lead to more homogeneous mixing and greater resistance to
metal coarsening at SOFC operating temperatures. In electrochemical tests of
plasma-sprayed metal-supported cells containing these anodes, peak power
densities as high as 0.6 W/cm2 were achieved at 750 deg C in humidified H2. In CH4,
power density was limited by the activity of the anodes. Stability in CH4 was
poor because of oxidation of the metal support and enhanced coking behaviour
resulting from interactions between Fe in the support and Co and Ni in the
anodes. When separated from the supports, the anodes demonstrated very low
coking rates in thermogravimetric analysis experiments in CH4.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/43496 |
| Date | 07 January 2014 |
| Creators | Cuglietta, Mark |
| Contributors | Kesler, Olivera |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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