Effect Of Electrode Modification On Performance Of Microbial Fuel Cell

Microbial fuel cell (MFC) is a novel green technology which can directly change substrates in wastewater to electronical energy. As a synthetical process of physical, electrochemistry and microbiology, the performance of MFC can be affected by many factors. Among these, the electrode material and biofilm on electrode are the two key factors.In this paper, the carbon felt was used as the basic electrode material. The novel organic material, silane coupling agents (SCAs) and conductive polymers were applied to modify carbon felt electrodes, and the influence of these materials to MFC performance was investigated. This paper mainly focused on the relationship among the electrode material, MFC performance and the biodiversity of electrode biofilm.Three kinds of SCAs KH550, KH580 and KH792 were used to modify the anodes of MFC. The amino-SCAs KH550 and KH792 can effectively improve MFC performance and the power densities were increased by 50% and 28.5% respectively. However, the sulfydryl-SCA KH580 did not promote MFC performance, even slowed the startup speed. According to the biodiversity analysis, the predominated phyla were Proteobacteria and Firmicutes on all anodes. After modified, the anode biodiversity became higher, and the change was mainly caused by different adsorption of bacteria on anode materials. Furthermore, in view of the structure of these SCA materials and anode biodiversity, functional groups, rather than alkyl chains, were responsible for the biodiversity variation.Two conductive polymers, polyaniline (PANI) and poly (aniline-co-o-aminophenol) (PANOA) were used to modify MFC anode, which promoted power densities by 35% and 18% respectively. Besides, both anode bacteria number and anode biodiversity became higher with the help of conductive polymers, which was probably responsible for the improved MFC performance.Polyaniline (PANI) and its three co-polymers poly (aniline-co-o-aminophenol) (PANOA), poly (aniline-co-2,4-diaminophenol) (PANDAP) and poly (aniline-1, 8-diaminonaphthalene) (PANDAN) were applied to modify both MFC abiotic cathode and biocathode. For abiotic cathode (Group A), these materials, due to their chemical catalysis for oxygen, increased power density by about 300%. The highest two were PANOA and PANDAP. While for biocathode (Group B), the highest were PANDAP and PANDAN, which promote the power density by 180%. With the help of chemical catalysis of conductive polymers and biocatalysis of cathode biofilm, the performance of MFC can be totally increased from 35.3 mW/m2 (Unmodified, abiotic-cathode) to 285 mW/m2 (PANDAN modified, biocathode). The functional groups on conductive polymers can endow new advantages to MFC performance. The-OH helped MFC showed less sensitivity to DO and pH change in cathode. While the-NH3 can enhance adsorption of bacteria, which enriched bacteria more rapidly and adsorb higher bacteria number.Exploring new effective and low cost electrodes is a hot topic in MFC study in future. The relationship among electrode material, MFC performance and biofilm biodiversity still need to be further discussed and more effort on it.