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| Author(s): |
Graziela Cristina Sedenho
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT) |
| Defense date: | 2021-02-25 |
| Examining board members: |
Frank Nelson Crespilho;
Ana Flavia Nogueira;
Marcos Jose Leite Santos;
Nelson Ramos Stradiotto;
Susana Ines Cordoba de Torresi
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| Advisor: | Frank Nelson Crespilho |
| Abstract | |
If we consider that part of cellular respiration is a model of energy obtention, it is envisioned that natural bioelectrochemical systems can be mimicked for the sustainable obtaining of electricity, as in biofuel cells (BFC) and aqueous batteries. Based on that, four topics in the state-of-the-art in electrochemical energy conversion are considered: (i) the electrode-electrolyte interface structure; (ii) the use of bioinspired molecules in a semi-solid aqueous battery; (iii) the use of biocatalysts on high-performance electrodes; and (iv) the use of microorganisms as autonomous entities for converting energy from organic substrates. In this context, this thesis explores these four topics in independent but complementary chapters: the detailed study about the effect of the structure and composition of carbon electrodes on the electrochemistry of quinones applied in aqueous-organic redox flow batteries and in BFC (in Chapter I); the development of an aqueous, semi-solid, non-corrosive and low toxicity microbattery (Chapter II); the use of bilirubin oxidase (BOD) in a gas diffusion electrode to reduce O2 to water (Chapter III); and the application of Saccharomyces cerevisiae in the conversion of chemical energy contained in carbohydrates into electricity (Chapter IV). It was concluded that edge-like defects and oxygenated functional groups, such as C-O and C=O, are crucial for obtaining high-performance carbon electrodes for energy conversion systems. In fact, when of flexible carbon fibers-based electrodes with these properties are used in aqueous semi-solid microbatteries, with organic and organometallic redox molecules in agarose hydrogel, a capacity of 0.79 mA h was obtained, which is able to meet the needs of small biomedical devices. In the case of biocatalysis to reduce O2 to water, the results indicate that the incorporation of BOD into a biogel matrix in a gas diffusion electrode can generate currents of 1.52 mA cm-2 and unprecedented operational stability, contributing to overcome critical issues for the practical application of BFCs. At last, a proposal for an extracellular electron transfer mechanism for Saccharomyces cerevisiae applied in microbiological BFC is shown. It was verified, for the first time, that the film of extracellular polymeric substances secreted by the yeast is able to confine flavoproteins that exchange charge with the electrode. Therefore, the results presented here cooperate to the advance in the field of bioelectrochemical and bioinspired energy conversion systems, as they contribute overcoming their critical issues and elucidating fundamental aspects in this area. (AU) | |
| FAPESP's process: | 15/22973-6 - Development of Microbial Fuel Biocells for Bioproduction and Oxidation of Ethanol |
| Grantee: | Graziela Cristina Sedenho |
| Support Opportunities: | Scholarships in Brazil - Doctorate |