Studies On The Membrane Separator And Electrode Materials For Microbial Fuel Cell Applications

Microbial fuel cell (MFC) is a technology for electricity generation where bacteria oxidize organic material and has good prospects in water treatment application. However, the output power of MFCs is only about 10-2-10’W/m2 now, and their application is severely restricted. The membrane separator and electrode materials are two important components of MFC system, and have a great influence on the electricity production performance. Herein, in this dissertation, two kinds of ion exchange membranes and a β-MnO2 modified graphite felt electrode material were prepared, and their performance in MFC were investigated.Firstly, a series of cation exchange membranes (CEM) with different ion exchange capacities (IECs) based on side-chain type sulfonated poly(aryl ether)s (sSPFAE) were prepared. Their properties in double chamber MFCs were investigated and compared with commercial CEM. The obtained sSPFAE membranes with thickness of 80 μm had IEC of 0.97～1.56 mmol/g, showed water uptakes about 20.9～41.7% at 30 ℃ and proton conductivities of 27.3-60.5 mS/cm, which were higher than those for commercial CEM (22 mS/cm,420 μm). The membranes also showed excellent dimensional stability (< 2%). For the MFC with sSPFAE membranes, the internal resistance was about 29～64 Ω1 based on power density peak and the slope of the polarization plots and decreased with the increase in IEC. All the sSPFAE membrane outperformed commercial CEM with columbic efficiency of 47.7～55%, and the maximum power output reached 657.3 mW/m2 for the membrane of sSPFAE-1.56. The anodic charge transfer resistance occupied about 76～88% of the total resistance of MFC according to EIS analysis based on analog equivalent circuit. The result of CV> EIS and electrode potential test indicated that the membrane separator have a great influence on the mass transfer and the anode charge transfer impedance.Secondly, a series of anion exchange membranes with different IEC based on random quaternary ammonium poly(aryl ether sulfone)s (rQPAES-OH) were prepared. Their properties in double chamber MFCs were investigated and compared with commercial AEM. The obtained rQPAES-OH membranes had IEC of 1.01-1.64 mmol/g, showed water uptakes about 33～58% at 30 ℃ and hydroxide ion conductivities of 14～22 mS/cm, which were higher than those for commercial AEM (21%,6.6mS/cm). For the MFC with rQPAES-OH membrane, the internal resistance was about 62～150 Ω based on power density peak and the slope of the polarization plots and decreased with the increase in IEC. All the rQPAES-OH membrane also outperformed commercial AEM, and the maximum power output reached 506.6 mW/m2 for the membrane of rQPAES-OH-1.64.Finally, β-MnO2 modified graphite felt electrode with different β-MnO2 loading (5-12.7 mg/cm2) were prepared by redox reactions and ultrasonic impregnation, and characterized by XRD, CV, SEM and EIS. Properties of these CF-βMnO2 electrodes as cathode material in double chamber MFC were investigated using air (O2) as electron acceptor. The results indicated that the CF-βMnO2 electrode exhibited better electrochemical behavior than the unmodified graphite felt electrode. The MFC using CF-βMnO2-12.7 as the cathode displayed maximum power density of 115.9 mW/m2 and internal resistance of 82 Ω.