Biological Fuel Cells (BFCs) use biological catalysts to convert chemical energy into electrical energy; enzymatic BFCs utilise enzymes as biocatalysts, which often results in the production of electricity from simple molecules such as glucose (in the presence of 02). Glucose oxidase (GOd) was utilised as a glucose-oxidising bioanodic enzyme. Initially, direct electron transfer (DET) of GOd was investigated using lightlyoxidised multi-walled carbon nanotubes (MWCNTs). Although GOd appeared to undergo DET, further investigation revealed that GOd did not undergo DET. Mediated electron transfer (MET) of GOd and flavin adenine dinucleotidedependent glucose dehydrogenase (F AD-GDH) was then investigated, using ferrocene (Fc) as an electron mediator. The resulting GOd and FAD-GDH bioanodes were then coupled with laccase and bilirubin oxidase (BOd) biocathodes, resulting in the enzymatic BFCs operating on glucose (in the presence of O2). Maximum power densities of 113.1 ± 1.5 /-LW cm-2 and 122.2 ± 5.8 /-LW cm-2 were obtained for GOd/laccase and F AD-GDHllaccase enzymatic BFCs, respectively (hydrostatically operating on 200 mM glucose in aerated citrate/phosphate buffer (PH 5.5)). Similarly, maximum power densities of 46.5 ± 2.8 /-LW cm-2 and 35.9 ± 1.3 /-LW cm-2 were obtained for GOd/BOd and FAD-GDHlBOd enzymatic BFCs, respectively (hydrostatic ally operating on 200 mM glucose in aerated citrate/phosphate buffer (pH 6.5)). It was also discovered that GOd produces significant quantities of H202 to deleteriously affect both laccase and BOd and their resulting bioelectrodes/biocathodes; this also results in decreased performances and operational stabilities of GOd-containing BFCs. H20 2 production (by GOd) was shown to rapidly inhibit laccase bioelectrode performances by up to 94%; 50% inhibition of laccase was observed at 1.94 mM H202. Although laccase and BOd are both significantly affected by H20 2, it is demonstrated that bioelectrocatalytic currents of laccase-containing cathodes that are lost in the presence of H20 2 can be recovered by the decomposition of H202 (by catalase). Lost bioelectrocatalytic currents of BOd-containing bioelectrodes cannot be recovered by that same treatment and the production of H20 2 should therefore be avoided. 111
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:616896 |
| Date | January 2014 |
| Creators | Milton, Ros Dean |
| Publisher | University of Surrey |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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