Publicação
Application of carbon nanomaterials in methane-producing bioelectrochemical syste
| Resumo: | Storage of renewable electricity in the form of methane (CH4) is a promising technology. Electrochemically assisted CH4 production from carbon dioxide (CO2) in a bioelectrochemical system (BES) allows the production of a biological fuel that can be stored and converted into electricity when necessary. In addition, CO2 is simultaneously captured contributing to mitigate climate change and global warming. However, this technology is still at an early stage with various technical and scientific problems and limitations that require further studies. Several aspects related to the biocathode performance, such as the low electron transfer rate between electrode and electrotrophs have been identified as important drawback to be overcame. The work developed in this thesis aimed to study the effect of carbon nanotubes (CNTs), as conductive material, on CH4 production in BESs. The production of CH4 was analyzed in two BESs, one working with a modified electrode (BESCNTs), in which CNTs were deposited, and another one that works as a control with a nonmodified electrode (BES-CTRL). The potential of CNTs to improve CH4 production was investigated under different electrochemical control modes, potentiostatic (at -1.0 V and -1.2 V vs. Ag/AgCl) and galvanostatic (at 2.7 mA and 7.5 mA). Parallel to the production of CH4, CO2 consumption, as well as the current-to-CH4, voltage and energy efficiencies were also evaluated. The results demonstrated that for both electrochemical control modes, the production of CH4 was higher in the presence of CNTs compared to the control assay. The current-to-methane efficiency varied between 15 % and 90 %, in both assays, while the voltage efficiency remained below 0.12 % and energy efficiency below 5.5 %. The study of the microbial community developed at the biocathode under galvanostatic control demonstrated a clear enrichment of methanogens (78 % in BES-CNTs and 86 % in BES-CTRL) compared to the initial inoculum (10 %), However, no significant differences were observed between both BES, since 98 % of the sample was classified as “unknown”. In conclusion, this work contributed with new insights on the effect of carbon nanomaterials to improve biocathode performance on BESs for CH4 production from CO2. |
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| Autores principais: | Fernandes, Bruna Rafaela Cardoso |
| Assunto: | Bioelectrochemical systems Carbon nanotubes CH4 production CO2 reduction Electromethanogenesis Eletrometanogénese Nanotubos de carbono Produção de CH4 Redução de CO2 Sistemas bioeletroquímicos |
| Ano: | 2019 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Storage of renewable electricity in the form of methane (CH4) is a promising technology. Electrochemically assisted CH4 production from carbon dioxide (CO2) in a bioelectrochemical system (BES) allows the production of a biological fuel that can be stored and converted into electricity when necessary. In addition, CO2 is simultaneously captured contributing to mitigate climate change and global warming. However, this technology is still at an early stage with various technical and scientific problems and limitations that require further studies. Several aspects related to the biocathode performance, such as the low electron transfer rate between electrode and electrotrophs have been identified as important drawback to be overcame. The work developed in this thesis aimed to study the effect of carbon nanotubes (CNTs), as conductive material, on CH4 production in BESs. The production of CH4 was analyzed in two BESs, one working with a modified electrode (BESCNTs), in which CNTs were deposited, and another one that works as a control with a nonmodified electrode (BES-CTRL). The potential of CNTs to improve CH4 production was investigated under different electrochemical control modes, potentiostatic (at -1.0 V and -1.2 V vs. Ag/AgCl) and galvanostatic (at 2.7 mA and 7.5 mA). Parallel to the production of CH4, CO2 consumption, as well as the current-to-CH4, voltage and energy efficiencies were also evaluated. The results demonstrated that for both electrochemical control modes, the production of CH4 was higher in the presence of CNTs compared to the control assay. The current-to-methane efficiency varied between 15 % and 90 %, in both assays, while the voltage efficiency remained below 0.12 % and energy efficiency below 5.5 %. The study of the microbial community developed at the biocathode under galvanostatic control demonstrated a clear enrichment of methanogens (78 % in BES-CNTs and 86 % in BES-CTRL) compared to the initial inoculum (10 %), However, no significant differences were observed between both BES, since 98 % of the sample was classified as “unknown”. In conclusion, this work contributed with new insights on the effect of carbon nanomaterials to improve biocathode performance on BESs for CH4 production from CO2. |
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