Study Onanode Performance Of Microbial Fuel Cell

Microbial fuel cells (MFCs) convert biomass energy into electrical energydirectly via electro-active micro-organisms which are gaining increasing attentions inmany areas for the past few years. MFC-based technologies such as microbialelectrolysis cell, microbial desalination cell, microbial reverse-electrodialysis cell andbiosensor have great promising applications. However, the low power density of MFCremains one of the main obstacles for their practical applications. So, the basic way tooptimize the anode that serves as both a carrier of bacteria and an electron collector inMFC is to facilitate the electrons transfer and thus to improve the MFC overallperformance. The anode surface characteristics, such as surface area, surface potential,surface biocompatibility, and surface roughness significantly affect the anodicreaction.Aiming at improving MFC’s anode poor performance by using nano-materials inthis paper, carbon nano-structured materials and polyaniline have been used to modifythe MFC anodes to increase specific surface and minimize the anode energy loss inthe system which could significantly improve the charge transfer efficiency and thebacterial biofilm loading as well as the overall performance of MFC. Based on theabove research purposes, the main work and results of this thesis are summarized asfollows: this paper’s(1) A two-chamber MFC was constructed whose cathode and anodecompartments are all of a volume of40mL. Its operation parameters (substrateconcentration, electrode spacing, operating temperature) are analyzed and optimized.Experiments show that MFC voltage curves are more regular, good reproducibilitywhen the substrate concentration are0.5g/L,1.0g/L. A cycle time of MFC with0.5g/L,1.0g/L substrate concentration are50h,72h respectively, and MFC with1.5g/L,2.0g/L concentration substrate are120h,160h. Poor reproducibility and longer cycletime are also unfavorable for studying other factors (different anode material andcathode catalytic activity, etc.) affect the performance of MFC. Therefore, thesubstrate concentration is choosen to be1.0g/L in all experiments of this paper. Inaddition, the operating temperature is set at25℃~30℃and electrode spacing is2cm.(2) The graphene with specific surface area of535m2/g is obtained by usingchemical reduction method. In the present study, the graphene modified carbon cloth (GNS/CC) is used as a microbial fuel cell anode and the performonce was comparedagainst that of the multi-walled carbon nanotubes modified carbon cloth(MWCNT/anode) and unmodified carbon cloth (CC/anode). The maximum powerdensity of microbial fuel cell with GNS/anode is1.4times and2times larger than thatof the MFC with MWCNT/anode and CC/anode respectively. The great improvementis attributed to the fact that the graphene has large specific surface area, high electricalconductivity and good biocompatibility.(3) A novel microbial fuel cell (MFC) anode is fabricated by electrochemicallyreducing graphene oxide (ERGNO) first and coating polyaniline (PANI) nano-fibersafterwards on the surface of carbon cloth (CC). ERGNO/CC is prepared using anelectrochemical synthesis method of reducing graphene oxide. UsingPANI-ERGNO/CC and ERGNO/CC as the MFC anodes, the maximum power densityobtained is1390mW/m2and1003mW/m2, respectively, which is3and2.1times ofthe MFC with CC anode. The electrochemical activities have been investigated by CVand electrochemical impedance spectroscopy (EIS). The electrodes are characterizedby scanning electron microscopy (SEM) and Raman spectroscopy (RS). The reason isthat PANI-ERGNO and ERGNO increase specific surface and minimize the anodeenergy loss in the system which could significantly improve the bacterial biofilmloading and decrease the internal resistance of MFC effectively as well as increase theoverall performance of MFC.