The effect of external resistance on biofilm formation and internal resistance in Shewanella inoculated microbial fuel cells

Abstract

External resistance is one of the important factors that affect the performance of microbial fuel cells (MFCs). In this study, bioelectrochemical and biofilm characterization was conducted for Shewanella oneidensis MR-1 inoculated MFCs with 250 Ω, 500 Ω, 2 kΩ, 6 kΩ and 22 kΩ resistors. Overall, a smaller external resistance resulted in a higher maximum power density and more riboflavin secretion. A maximum power density of 136.8 ± 3.1 mW m⁻² was achieved when MFCs were operated with a 500 Ω resistor, which was 3.7 times that with a 22 kΩ resistor. Electrochemical impedance spectra (EIS) analysis verified an increased internal resistance with a higher external resistance. Meanwhile, more biofilm mass and extracellular polymer substances (EPS) were confirmed on the MFC anode with a higher external resistance.