Electrochemical impedance spectroscopy studies on microbial fuel cells

Recent design improvements helped increase the power densities of Microbial Fuel Cells (MFCs) by orders of magnitude by decreasing the internal ohmic resistance. With the ohmic resistance of the MFC systems no longer a dominant issue, identification of other intrinsic resistances is the need of the hour. Electrochemical Impedance Spectroscopy (EIS) is a useful tool to delineate the individual contributions from different resistances to the overall cell impedance. Preliminary EIS experiments were conducted with acetate fed two-chamber MFC inoculated with Geobacter Sulfurreducens and using a ferricyanide catholyte. Results showed that the anode played a dominant role in limiting the kinetics of the bio-electrochemical reaction, thereby contributing to the majority of the polarization loss. Based on the equivalent electrical circuit fitting of the EIS data, parameters such as charge transfer resistance, membrane resistance and exchange current density have been estimated for the first time for the case of MFCs.