Electricity production and electrochemical impedance modeling of microbial fuel cells under static magnetic field

Two-chamber microbial fuel cells (MFCs) were exposed to static magnetic field (MF) of field strengths 0 mT, 100 mT, 200 mT, and 300 mT, and the electricity production of the MFCs under the influence of the MF was investigated using electrochemical methods. The results show that the start-up periods of MFCs in MF were shorter than that without. The MFC with a 100-mT MF needed the shortest time (7 days) to obtain a stable voltage output. The maximum power density of 1.56 W m−2 was for a field strength of 200 mT, which was the best among the MFCs. The impact of the MF on the charge transfer resistances (Rct) of the anode, cathode, and whole MFC was analyzed by electrochemical impedance spectroscopy (EIS). A new method was developed to extend the equivalent circuit (EC) model to the whole MFC by connecting the anode and cathode models in series. The simulated results show that anode Rct values are much higher compared than at the cathode. The cell and anode Rct values were reduced by 56.6% and 57.2%, respectively, for the 200-mT MF. It was also found that there is an optimal intensity MF range for the microorganisms. ► MFCs were exposed to magnetic fields to improve the electricity production. ► The influences of magnetic fields with different intensities were investigated. ► Each component of reactors was tested by EIS. ► The equivalent circuit to fit EIS of whole cell is on the basis of those of anode and cathode. ► The primary influence of magnetic field on MFCs is the reduction of anode activation loss.