With annual global energy consumption predicted to double by 2050 and CO2 emissions having already reached crisis point, the growing demand for renewable and environmentally clean power sources has been propelled to the forefront of academic and industrial research. One strategy currently under investigation is the employment of enzymes in enzymatic fuel cells (EFCs), which convert chemical energy to electrical energy. This research focused on comparing the use of different protein-stabilising agents in low-cost bilirubin oxidase (DOD) from Mycothecium verrucaria cathodes with sandwich architcctures, for biocatalysis of the electrochernical oxygen reduction reaction (ORR). As a novel route towards EFC cost reduction, Super P (carbon black powder, CBP) was initially selected as an electronically conductive enzyme support material. To increase direct electron transfer, COOH functionalisation of the CDP was investigated and characterised with ATR-FTIR, CHN and thermogravimetric analysis and the Boehm titration technique. Chemical oxidation yielded surface COOH concentrations ranging between 0.16 - 1.70 mmol g-I, which was determined with cyclic voltammetry (CV) to be outside of the sui table range for application within BOD cathodes. This resulted in the use of multi -walled carbon nanotubes (MWCNTs) as the enzyme supp0l1 material. The effect of several room temperature ionic liquids (RTlLs) on BOD activity was also investigated, resulting in the novel identification of three RTlLs that are BOD-compatible in the absence of water: l-ethyl-3-methylimidazolium ethylsulfate (EMIM-EtS04), l-elhyl-3- methylimidazolium diethylphosphate (EMIM-Et2P04) and 1,3-methylimidazoliulll dimethylphosphate (MMIM-Me2-P04). Two BOD cathodes, utilising the non-ionic surfactants (N ISs) Triton X-l00 and Tween 20, were developed, optimised and characterised. 1'riton X-lOO was detennined to be the favourable NIS for three-layer BOO cathode fabrication, compared to Tween 20, especially with respect 10 electrode current densities (-81 vs. -60μA cm-2 at 0.3 V vs. Ag/AgCI at pH 5.0) attributed to the BOD-catalysed ORR. Chronoamperornetric studies over a period of 8 days showed no difference between the stability of the two BOD cathodes.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:610910 |
| Date | January 2014 |
| Creators | Markowska, Anna Lucyna |
| Publisher | University of Surrey |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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