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Improvements in Fabrication and Materials for Solid Oxide Fuel Cells
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- Author / Creator
- Amiri, Mohammad Taghi
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Solid oxide fuel cells have numerous advantages, including higher efficiencies, fuel diversity, and lack of need for expensive catalysts compared to other fuel cells. Yet the lower performance and lack of durability in the long term still hinder its practical usage. By lowering the operating temperature, the system's longevity can increase dramatically. The downside is that maintaining the acceptable performance requires either the development of new materials for cell components or improving the structural and functional characteristics of electrodes. This study pursues both approaches.
First, a new proton conductor electrolyte based on Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-δ has been used in a SOFC. Compared to other studies, higher power output was achieved. The chemical compatibility in moisture and carbon dioxide was also studied in detail.
Second, the combination of microwave irradiation in conjunction with salt infiltration was used for rapid catalyst synthesis inside the porous YSZ layer. Compared to the traditional sintering method with an electric resistance furnace, this approach increased the cell's performance. It was concluded the enhancement of this technique came from the enhanced morphology of the resulting particles.
Next, using direct microwave heating on a cermet support to enable direct microwave sintering without the use of any susceptor was conducted. This method was used on poor microwaved coupled materials, which would be extremely difficult and expensive to sinter using traditional methods. This study shows the successful integration of this method for YSZ.
The chemical compatibility of components was investigated by powder X-ray diffraction and Rietveld refinement. Electrochemical examinations under air/hydrogen were conducted. Specifically, electrochemical impedance spectroscopy was used to examine the electrochemical performance of the full cell at different temperatures in this study. Detailed analysis was done to deconvolute the impedance results, including Distribution of Relaxation Times. Microstructures of the prepared cells were studied using a field-emission scanning electron microscope.
A similar setup to a solid oxide fuel cell was used to convert titanium dioxide to nitride electrochemically. Titanium nitride offers excellent properties such as high electrical conductivity and corrosion resistance up to 800 °C. TiN might address several key disadvantages of fuel cells, such as using direct hydrocarbon fuels and long-term electrode grain growth. We successfully converted a titanium dioxide support to titanium nitride in the presence of ammonia. This method offers a much cheaper sintering process, and the same cell can later be used as a fuel cell or electrolyzer.
Finally, an enhanced method for electrode deposition into a porous layer was developed. This method exerts an external electric field, forcing the infiltration precursor into the porous matrix and depositing the catalyst. The advantage of this method is it can be used for a thick layer. Another advantage is that it can deposit a higher amount of catalyst than conventional infiltration. The electrochemical performance improved despite this method needing further optimization. -
- Graduation date
- Fall 2022
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.