Impact of external resistance acclimation on charge transfer and di ff usion resistance in bench-scale microbial fuel cells

Reducing the external resistance (Rext) for microbial fuel cell (MFC) acclimation can substantially alter the anode performance in terms of charge transfer (R-CT), diffusion (R-d) and total anode resistance (R-An). Electrochemical impedance spectroscopy (EIS) was used to quantify anode impedance at different set potentials. Reducing R-ext from 50 Omega to 20 Omega during acclimation reduced RCT by 31% (from 6.12 +/- 0.09 m Omega m(2) to 4.21 +/- 0.03 m Omega m(2)) and Rd by 18% (from 3.4 +/- 0.2 m Omega m(2) to 2.8 +/- 0.1 m Omega m(2)) at a set anode potential of -115 mV during EIS. Overall RAn decreased by 27%, to 5.13 +/- 0.02 m Omega m(2) for acclimation at 20 Omega, enabling the anode to achieve 38% higher current densities of 29 +/- 1 A m(-2). The results show a clear dependence of acclimation procedures and external resistance on kinetic and diffusion components of anode impedance that can impact overall bioelectrochemical performance.