Publicação
Desenvolvimento de uma célula de biocombustível enzimática de glicose / oxigénio baseada em transdutores de minas de grafite
| Resumo: | Nowadays, society is heavily dependent on multiple types of energy that are spent in numerous applications. Most of this energy is derived from non-renewable sources such as nuclear and fossil fuels that may represent serious environmental, social and economic concerns. The future of energy supply depends on the innovative design of green, sustainable, and efficient systems for the conversion of clean and readily available energy sources. Biofuel cell is a sustainable, micro-energy production technology with promising applications in the biotechnological field and small consumable electronics. It is based on the application of biological entities such as microorganisms or enzymes in electrochemical transducers to convert the chemical energy of specific compounds into electrical signals. Particularly, enzymatic glucose/O2 biofuel cells have been widely studied due to their promising implantable applications since energy can be extracted from biological fluids to power critical devices such as pacemakers. The main objective of this work was the development of an enzymatic glucose/O2 biofuel cell using low-cost pencil graphite electrodes (PGE) for the enzymatic transduction. Bioanode was based on the immobilization of glucose oxidase (GOx) enzyme for catalysis of glucose fuel while biocathode was based on the immobilization of bilirubin oxidase (BOx) enzyme for reduction of the oxidant O2. The experimental work began with the electrochemical characterization of PGE and comparison with conventional electrodes. Good voltammetric results were obtained for PGE in terms of cathodic/anodic peak intensities, peak-to-peak separation (∆Ep) and electron transfer rate constant (k0 ) justifying therefore their selection as a transducer for the immobilization of enzymes. In order to improve the electrochemical performance of PGE, nanostructuration of the electrode surface was assessed using different carbon nanomaterials (multi-walled carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs), reduced graphene (rGO)) through cyclic voltammetry (CV). Prior to biofuel cell assembly, the biocathode and the bioanode were individually characterized as biosensors for the respective enzyme substrates. Therefore, the bioelectrode for O2 was first developed by immobilizing BOx into a previously modified PGE (PGE-rGO-MWCNTs) using a pyrene-based succinimidyl ester (PBSE) cross-linker. After assessing enzyme immobilization by CV, O2 was detected by amperometry achieving a sensitivity of 600 µA.mM-1 .cm-2 and a limit of detection of 0.1 mM. When applied as a biocathode, the polarization curves resulted in an open circuit potential (OCP) of 0.52 V vs Ag/AgCl and generated a maximum current density of 170 µA.cm-2 in the presence of O2. The bioelectrode for glucose was fabricated in a similar way, however, using SWCNTs instead of MWCNTs (PGE-rGO-SWCNTs-PBSE-GOx). Although being efficiently immobilized in the electrode surface enabling direct electron transfer, the amperometric analysis revealed some instability and unreproducible problems, requiring the use of a mediator to facilitate the electron transfer between the enzyme and the electrode. In this mediated condition the sensitivity achieved was 55 µA.mM-1 .cm-2 and the limit of detection was 0.09 mM. Finally, the GOx and BOx bioelectrodes were assembled as bioanode and biocathode in a glucose /O2 biofuel cell. In mediated electron transfer conditions, the membraneless biofuel cell achieved an OCP of 0.45 V and generated a power density of 26 µw.cm -2 . A membraneless glucose/O2 biofuel cell was therefore successfully fabricated though requiring the use of a diffusional mediator to achieve maximum power. |
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| Autores principais: | Tavares, Miguel Ângelo Lopes |
| Assunto: | Biofuel cell Biosensors Enzymes Carbon nanomaterials Pencil graphite electrodes Células de biocombustível Biossensores Enzimas Nanomateriais de Carbono Elétrodos de Minas de Grafite |
| Ano: | 2020 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Instituto Politécnico do Porto |
| Idioma: | inglês |
| Origem: | Repositório Científico do Instituto Politécnico do Porto |
| Resumo: | Nowadays, society is heavily dependent on multiple types of energy that are spent in numerous applications. Most of this energy is derived from non-renewable sources such as nuclear and fossil fuels that may represent serious environmental, social and economic concerns. The future of energy supply depends on the innovative design of green, sustainable, and efficient systems for the conversion of clean and readily available energy sources. Biofuel cell is a sustainable, micro-energy production technology with promising applications in the biotechnological field and small consumable electronics. It is based on the application of biological entities such as microorganisms or enzymes in electrochemical transducers to convert the chemical energy of specific compounds into electrical signals. Particularly, enzymatic glucose/O2 biofuel cells have been widely studied due to their promising implantable applications since energy can be extracted from biological fluids to power critical devices such as pacemakers. The main objective of this work was the development of an enzymatic glucose/O2 biofuel cell using low-cost pencil graphite electrodes (PGE) for the enzymatic transduction. Bioanode was based on the immobilization of glucose oxidase (GOx) enzyme for catalysis of glucose fuel while biocathode was based on the immobilization of bilirubin oxidase (BOx) enzyme for reduction of the oxidant O2. The experimental work began with the electrochemical characterization of PGE and comparison with conventional electrodes. Good voltammetric results were obtained for PGE in terms of cathodic/anodic peak intensities, peak-to-peak separation (∆Ep) and electron transfer rate constant (k0 ) justifying therefore their selection as a transducer for the immobilization of enzymes. In order to improve the electrochemical performance of PGE, nanostructuration of the electrode surface was assessed using different carbon nanomaterials (multi-walled carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs), reduced graphene (rGO)) through cyclic voltammetry (CV). Prior to biofuel cell assembly, the biocathode and the bioanode were individually characterized as biosensors for the respective enzyme substrates. Therefore, the bioelectrode for O2 was first developed by immobilizing BOx into a previously modified PGE (PGE-rGO-MWCNTs) using a pyrene-based succinimidyl ester (PBSE) cross-linker. After assessing enzyme immobilization by CV, O2 was detected by amperometry achieving a sensitivity of 600 µA.mM-1 .cm-2 and a limit of detection of 0.1 mM. When applied as a biocathode, the polarization curves resulted in an open circuit potential (OCP) of 0.52 V vs Ag/AgCl and generated a maximum current density of 170 µA.cm-2 in the presence of O2. The bioelectrode for glucose was fabricated in a similar way, however, using SWCNTs instead of MWCNTs (PGE-rGO-SWCNTs-PBSE-GOx). Although being efficiently immobilized in the electrode surface enabling direct electron transfer, the amperometric analysis revealed some instability and unreproducible problems, requiring the use of a mediator to facilitate the electron transfer between the enzyme and the electrode. In this mediated condition the sensitivity achieved was 55 µA.mM-1 .cm-2 and the limit of detection was 0.09 mM. Finally, the GOx and BOx bioelectrodes were assembled as bioanode and biocathode in a glucose /O2 biofuel cell. In mediated electron transfer conditions, the membraneless biofuel cell achieved an OCP of 0.45 V and generated a power density of 26 µw.cm -2 . A membraneless glucose/O2 biofuel cell was therefore successfully fabricated though requiring the use of a diffusional mediator to achieve maximum power. |
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