Activity: Lecture and oral contribution
Solid oxide fuel cells (SOFCs) efficiently convert chemical energy directly into electricity using fuels ranging from pure hydrogen to diesel. With the use of bio-fuels, SOFC electricity production is CO2neutral. When operated in reverse as solid oxide electrolysis cells, it is possible to store excess electricity from renewable sources in the form of CO2neutral fuels (e.g. for the transport sector) and simultaneously “load balance” the electricity grid. SOFCs are now on the verge of market entry for a variety of heat and power production applications. SOFCs are complex multilayer structures (typically planar). In the electrochemically active layers, a dense ion-conducting ceramic electrolyte separates a porous anode and cathode that are typically electron and ion-conducting composites. The electrolyte becomes an ionic conductor at high temperatures (> 600°C) and the electrodes are exposed to harsh atmospheres during operation. These conditions place stringent materials demands on oxidation resistance, thermal expansion co-efficient matching, creep resistance, mechanical strength, materials compatibility, and electronic and ionic conductivity. The fundamentals of SOFC operation, production, cell-testing and electrode characterisation will be presented in the context of SOFC stacks and systems. Each of these aspects are critically interlinked from a materials science perspective. SOFC design considerations include materials compatibility, production methods, performance, durability, operational requirements, and system cost. Characterisation is an important design step for SOFC performance and durability. Post-mortem investigations commonly use electron microscopy of cell components in combination with cell test data to determine the performance limiting mechanisms. Traditionally, electron microscopy is performed in 2D using scanning and transmission microscopes. Advances in focused ion beam-scanning electron microscopy (FIB-SEM) have allowed nanometre-scale 3D tomographicreconstruction of electrodes, and the possibility to fully describe their stochastic structure and phase percolation. Recent developments in 3D reconstruction methods will be presented in the latter half of the talk.
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