Mechanism And Application Of Exoelectrogen-electrode Interaction In Microbial Fuel Cell

Microbial fuel cell (MFC) is an emerging process that can generate electricity with simultaneous organic matter removal from domestic and industrial wastewaters. All such time serried contributions awakened the general interest in MFCs and triggered a spiral of research achievements that have steadily raised the performance levels by several orders of magnitude in less a decade.To effectively apply MFC in practice, challenges including low power output and high cost have to be tackled first. Along with the optimization of material and configuration, ohmic resistance was sharply decreased. As a result, activation resistance originated from the electrode reactions became the limiting factor of a higher power output. For the cost, using biocathode instead of noble metal cathode was one of the solutions. All these mentioned above urged the illustration of the interaction mechanism between exoelectrogen and electrodes. The objective of this work is: (i) to investigate the interaction mechanism between exoelectrogen and electrodes; (ii) to find strategies to improve power out of MFCs by decreasing the activation resistance; (iii) to develop biocathode using carbon dioxide as the electron acceptor.During investigation of the interaction mechanism between exoelectrogen and electrodes, a model strain Geobacter sulfurreducens was used. By using quantative analysis methods such as biomass determination, polarization curve, cyclic voltammetry and electrochemical impedance spectroscopy, it was shown that a strong relationship existed between the growth of exoelectricigen and performance of the MFC in the initial stage of biofilm formation. Furthermore, the effect of anode potential on the performance of MFC and growth of exoelectrogen was investigated. The anode potential regulated power generation and growth of exoelectrogen, also an optimal anode range was observed.Enhanced performance of MFC was achieved by applying the interaction mechanism. By using the specific electron transfer chain of phototrophic bacteria, here we enriched a phototrophic exoelectrogenic consortium that can produce electricity in an"H"typed MFC at a high power density (2650 mW m-2, normalized to membrane area) in light, which was 8 fold of that produced by non-enriched consortium in the same reactor. This power density was also the highest among the similar reactors. These results confirmed that regulating the growth of exoelectrogen can affect the MFC activation resistance. A microbial excreted mediator assisted the electron transfer to the electrode. During the experiment, the accumulation of the mediator over time enhanced the electron transfer rate. The HPLC, GC/MS and excitation-emission matrix fluorescence spectroscopy results indicated indole group containing compound representing the dominant mediator component.In this research, a novel biocathode was developed to show a solution for cutting off cost. It is shown here that by illuminating it is possible to develop a biocathode that uses dissolved carbon dioxide (bicarbonate) as acceptor. Bicarbonate was reduced in stoichiometric agreement with current generation, with 0.28±0.02 moles of bicarbonate reduced per mole of electrons. When this biocathode was used in a"H"typed MFC, a power density of 750 mW m-2 was produced. This was 15 fold higher than that achieved with a plain cathode.