Research on minimizing the MFC internal resistance via a shared electrode MFC-MEC coupling system

Abstract

Although microbial fuel cells (MFCs) are a very clean electricity-producing bioelectrochemical technology, their large internal resistance limits their power generation capacity. To reduce the MFC internal resistance, according to the principle of favorable electric field, a microbial electrolysis cells (MECs) was coupled with MFC to form two kinds of MFC-MEC coupling systems: a shared anode MFC-MEC system (SA-MFC) and a shared cathode MFC-MEC system (SC-MFC). Compared with those of the uncoupled MFC, the total internal resistances (Rtol) of the SA-MFC and the SC-MFC were 2119.04 Ω and 2416.44 Ω, respectively, lower than that of the uncoupled MFC (3392.05 Ω). The average working voltages of the SA-MFC and the SC-MFC reached 121.40 mV and 100.43 mV, respectively, which were 41.71% and 17.23% higher than that of the uncoupled MFC (85.67 mV), and the maximum power output reached 121.03 mW and 94.09 mW, respectively, which were 1.93 times and 1.50 times that of the uncoupled MFC (62.58 mW), indicating that the SA-MFC had optimal power production performance. The reasons for these differences were that the external electric field provided by the MEC created an additional driving force for the electrode reaction, extracellular electron transfer and liquid phase mass transfer, resulting in weakened electrode polarization. This research provides a new way to reduce the internal resistance of MFCs and increase their power output.