With the current interest in alternative methods of energy production and increased utilization of existing energy sources, microbial fuel cells have become an important field of research. Microbial fuel cells are devices which harvest electrons from microorganisms created by their enzymatic oxidation of complex carbon substrates or consumed by their reduction of chemical oxidants. Microbial fuel cells with photosynthetic biocathodes are of particular interest due to their ability to simultaneously produce electricity and hydrocarbons while reducing carbon dioxide.
Most species of microorganisms including many bacteria and yeasts require exogenous electron transfer mediators in order to allow electron transfer with an electrode. While adding such chemicals is simple enough at a lab scale, problems arise with chemical costs and separation at a larger scale. The goal of this research was to develop electrodes composed of a robust material which will eliminate the need for added soluble electron mediators in a photosynthetic biocathode microbial fuel cell.
Electrodes made from stainless steel 304L have been coated in a conductive polymer (polypyrrole) and an immobilized electron transfer mediator (methylene blue) and tested chemically for stability and in a microbial fuel cell environment for use in bioanodes and biocathodes. The use of these immobilized mediator in the photosynthetic biocathode increased the open circuit voltage of the cell from 0.17 V to 0.24 V and the short circuit current from 8 mA/m2 to 64 mA/m2 (normalized to the geometric surface area of the electrode) when compared to using the same mediator in solution. The opposite effect was seen when using the electrodes in a bioanode utilizing Saccharomyces cerevisiae. The open circuit voltage decreased from 0.37 V to 0.31 V and the short circuit current decreased from 94 mA/m2 to 24 mA/m2 when comparing the immobilized mediator to soluble mediators. The impact of the membrane and pH of the anode and cathode solutions were quantified and were found to have much less of an effect on the internal resistance than the microbial factors.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-08092011-143442 |
| Date | 17 August 2011 |
| Creators | Godwin, Jonathan M |
| Contributors | Burgess, Ian, Evitts, Richard, Nemati, Mehdi, Phoenix, Aaron |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-08092011-143442/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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