微生物燃料电池（Microbial fuel cell，MFC）是近年迅速发展起来的一种新型燃料电池技术，将之应用于污水处理领域，可以在降解污染物的同时回收电能，因此受到广泛的关注。现阶段制约MFC工程应用的关键问题主要是产能偏低和造价较高。随着反应器结构材料的优化，源于电极表面微生物催化反应的活化内阻逐渐成为制约功率的关键；造价偏高主要来自于阴极使用的贵金属催化剂，利用微生物代替金属催化剂形成生物阴极可有效降低造价。这两个问题的核心均涉及产电菌与电极的契合和相互影响，因此本论文的目的即研究产电菌与电极的作用机制，并对MFC面临的两个关键问题进行探索性研究。在产电菌与电极的作用机制研究部分，以产电模式菌Geobacter sulfurreducens为研究对象，利用生物量测定、生物膜观察、极化曲线、循环伏安曲线和电化学阻抗谱等分析手段，定量解析了产电菌能量代谢与MFC产电的相互关系。研究表明在生物膜发展初期产电菌生物量和MFC的极限电流呈相关关系。改变阳极电势调控产电菌能量代谢对MFC的启动过程、产电性能和产电菌的生长均有显著影响，并存在最佳的电势范围。本研究在阳极富集获得了一类高产电能力的光合产电菌，在两瓶型MFC中输出功率密度可达2650 mW m-2，是黑暗对照条件的8倍，在同类反应器中亦位居前茅。推测由于光合菌的特殊电子传递途径降低了电子供体的实际电势，从而促进产电菌的生长并提高了输出功率，本研究再次证明调控产电菌的能量代谢可影响MFC的活化内阻。研究表明本试验条件下光合产电菌的机理是介体传递型，气质联用和三维荧光光谱的结果显示该介体属于吲哚类物质。本研究首次实现了以二氧化碳作为电子受体的生物阴极过程，为降低MFC造价提供了一条新的思路。针对阴极产电菌的能量代谢需求，输入光能克服能量壁垒，实现了微生物催化的阴极产电和固碳过程。碳酸氢钠的去除和累积电量成明显的化学计量关系，为0.28±0.02 mol C mol-1 e。在两瓶型MFC中，使用该生物阴极，输出功率密度可达750 mW m-2，比空白对照提高了15倍。
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.
