Microbial fuel cells are bioelectrochemical systems producing electrical energy from microbial reactions. These systems have been considered as renewable energy sources; however, questions remain on how these systems can be effectively optimized for practical applications. Several electrochemical tests were employed in this study to investigate the MFCs performance. Four double-chamber cells were assembled as follows: MFC1 contained anode solution only, MFC 2 contained anode solution plus substrate, MFC 3 contained anode solution and substrate inoculated with biocatalyst, and MFC4 a one year old cell operated on a regular inoculation and substrate feeding schedule. All four cells contained phosphate buffer solution in cathode chambers. The polarization curves were obtained based on LSV from -15 to +700 mV and from +15 to -700 for both anode and cathode respectively, at a scan rate of 1mV/s to determine the maximum attainable power in each MFC. Then tafel curves and exchanging currents were obtained from polarization data to study the reaction rates in different assemblies. Various internal resistances of anode were separated using EIS at the OCPa in a frequency range of 100KHz- 10mHz. The CV was performed for both anode and cathode using a potential range of -700 to +700 mV (vs. SCE) at a scan rate of 1 mV/s. This analysis clearly demonstrated the activity of biocatalyst in power production. Overall, the results showed that in an MFC, power is produced once the reactor is inoculated with appropriate microbial culture. Electrochemical tests indicated no biological redox activity prior to inoculation. With the addition of cell suspension, reaction rate and consequently maximum current increased from 92.5 to 142mA/cm2 indicating that substrate oxidation in anode and oxygen reduction in cathode was the dominant process in the reactor. The i0 values confirmed this finding. In Bode plots, reduction of the impedance and the phase angle at low frequency, demonstrated reduction of polarization resistance of the anode ( ) approximately 6.5 and 11.4 times less in MFC 2 and MFC 3 than MFC1, respectively. In MFC4 increased because of the formation of biofilm.

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