Solid oxide fuel cells (SOFCs) are a promising power conversion technology that has the benefit of high efficiency and the ability to work on a range of fuels, including natural gas. However, if run on hydrocarbon fuel under non-optimised conditions the anode can undergo carbon deposition (coking) which leads to a loss in performance. Research is required to understand the complex nature of the carbon formation process in order to develop superior electrode materials and avoid its formation. To do this, a range of ex situ analytical techniques are available; however, these do not allow the process to be studied in real time within the studied environment of the SOFC. The gallium orthophosphate crystal microbalance (GCM) is a piezoelectric device capable of acting as a microbalance sensor up to 900 °C. This work describes the development of the GCM for studying coke deposition on nickel substrate, as a mimetic of the cermet electrodes used for SOFC anodes. A novel holder system was design and produced to allow operation of both the GCM and SOFC at high temperatures in a range of gas environments. Change in oscillation frequency associated with temperature and gaseous environment was studied and found to be conducive to the intermediate temperature SOFC operating environment. Surface development of the GCM to produce a nickel catalytic surface has shown the ability to detect coke formation for the application of SOFC anodes. The degradation of electrochemical performance due to deposition of carbon onto symmetrical SOFCs is measured using electrochemical impedance spectroscopy (EIS). Direct correlation is observed between the frequency shift of the sensor and the change in resistance to charge transfer of the SOFC anode. Evidence of an induction period following exposure to methane has been shown in SOFC anodes.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:626114 |
| Date | January 2013 |
| Creators | Millichamp, J. S. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1387821/ |
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