Polarization behavior of microbial fuel cells under stack operation

The polarization behavior of microbial fuel cells (MFCs) was evaluated under different stack operation modes, including series, parallel, series–parallel, and parallel–series. During the stack operation, voltages of individual MFCs, subunit stacks, and overall stacks were recorded as a function of the current. Meanwhile, the potentials of individual MFCs’ anode and cathode were also determined via Ag/AgCl electrodes to study the change in potentials under stack operations. The results demonstrated that the MFCs with relatively low ability to generate current were easier to suffer polarity reversal in the series stack, which was confirmed in the series subunit of the series–parallel stack. MFCs with high electroactivity would be enhanced to generate larger maximum power; however, MFCs with low electroactivity outputted smaller maximum power in a parallel stack. The changes in individual MFCs’ behavior under stack operation mode were determined primarily caused by the influences on the behavior of the anode. Results of the present study provide valuable information for optimization of stack operation of MFCs.