<p> The exploration of cathode materials and fabrication methods plays an important role in the development of solid oxide fuel cell (SOFC) technology. The objective of this study is first to optimize the cathode microstructure by the impregnation method, and then investigate the potential application of copper manganese spinel as a new cathode material with optimized microstructure and explore the reaction mechanism of the cathodes.</p> <p> The impregnation method was employed to fabricate a composite cathode with electrocatalyst particles dispersed in a framework of electrolyte material. The impregnation method is relatively easy to apply and yield the optimized microstructure, allowing extended three phase boundary length and absence of secondary phase formation during fabrication.</p> <p> The polarization performance of copper manganese spinel (CMO) impregnated YSZ cathodes was examined by adjusting catalyst particle size, electrode thickness and catalyst content. A critical thickness of 16.9±2.0 μm for the CMO-YSZ composite cathode was calculated from Tanner's model. Decreased catalyst particle size and a thickness close to the critical value were found to eliminate polarization loss. The composite cathode with 50 wt% CMO impregnation showed a polarization resistance as low as 0.3 Ωcm^2 at 750°C. At 800°C, an SOFC with CMO-YSZ composite cathode had a power density of 172 mW/cm^2, which was 2.5 times higher than the cell with the traditional LSM-YSZ composite cathode under the same conditions.</p> <p> The cathode reaction mechanism of CMO-YSZ and strontium doped lanthanum ferrite (LSCF) impregnated Gd doped ceria ( CGO) composite cathodes was studied, using impedance spectroscopy, cyclic voltammetry and current interruption
techniques. Surface diffusion and mass transfer were determined to be the rate controlling
steps for CMO-YSZ composite cathode at low and high temperatures, respectively. A low frequency process at low temperatures and at least two processes at high temperatures were identified as rate determining steps of LSCF -CGO composite cathodes. A cathodic current activation effect was observed on CMO-YSZ cathode under current passage. The catalytic activity of CMO was enhanced by the cathodic current and the effect existed in both long-term and short-term experiments.</p> <p> The results of this study suggest that copper manganese spinel has attractive properties as a new catalyst material for the cathodic reaction with the composite structure obtained by the impregnation method.</p> / Thesis / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/21764 |
| Date | 08 1900 |
| Creators | Zhang, Qi |
| Contributors | Petric, Anthony, Materials Science and Engineering |
| Source Sets | McMaster University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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