Electrokinetic behaviour of conducting polymer modified stainless steel anodes during the enrichment phase in microbial fuel cells

Abstract Two of the major bottlenecks in achieving large-scale power generation with MFCs to date are the low power output and the usually long start-up time, both of which are mainly associated with poor bacterial kinetics and inefficient anode electrode materials. We have demonstrated in this study that the electron transfer kinetics of stainless steel (SS) can be significantly improved by modification with polyaniline (PANi) and polypyrrole (PPy). Furthermore, we have demonstrated that the kinetics of the bacterial growth can be significantly enhanced by the application of a carefully selected external resistance ( R ext ), resulting in significantly shorter start-up time. The half-cell reactors used for the investigations were enriched under different conditions including without R ext (Open circuit mode), with R ext  =  R int (Ohmic region), and with very low R ext (mass transfer region). The MFC anodes enriched under R ext  =  R int gave maximum exchange current density ( j 0max ) on the 4th day of operation. The calculated j 0max for SS wool, PANi-wool, and PPy-wool anodes were 0.3 ± 0.2 A m −2 , 10.5 ± 0.4 A m −2 and 5.0 ± 0.4 A m −2 , respectively. The lowest charge transfer resistance ( R ct ) of 0.23 Ω cm −2 was obtained with SS/PANi-wool anode which exhibited the highest electron transfer kinetics and better compatibility than SS/PPy-wool. The high current drawn from the system during the biofilm establishment phase did not support electroactive biofilm formation because it prevented the growing anode-respiring bacteria (ABR) from providing sufficient electron flow to the counter electrode.