Accurate measurement of internal resistance in microbial fuel cells by improved scanning electrochemical impedance spectroscopy

In this study, a scanning electrochemical impedance spectroscopy (EIS) technique is proposed to confirm the variation of internal resistance (R_int) including charge transfer resistance (R_ct) and ohmic resistance (R_ohm) under various working conditions of microbial fuel cells (MFCs). In order to establish a scanning EIS method, overall R_int of the system and R_ct of anode and cathode were measured by EIS under various external resistance conditions. Using this method, it was confirmed that the R_ohm and R_ct of each electrode changed variably. Based on the use of scanning EIS, the rapid increase in the R_ct of anode was found to be the main cause of a power-overshoot. As such, the use of scanning EIS is a methodology that can provide data to understand undesirable phenomena such as power-overshoot and voltage reversal which are generated by the typical operational characteristics of MFCs when used in scale up experiments. The use of scanning EIS should be applied as a novel measurement technique that improves on the use of the open circuit mode based EIS methods.