Impact of external resistance acclimation on charge transfer and diffusion resistance in bench-scale microbial fuel...

Reducing the external resistance (R_ext) 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 Ω to 20 Ω during acclimation reduced R_CT by 31% (from 6.12 ± 0.09 mΩ m² to 4.21 ± 0.03 mΩ m²) and R_d by 18% (from 3.4 ± 0.2 mΩ m² to 2.8 ± 0.1 mΩ m²) at a set anode potential of -115 mV during EIS. Overall R_An decreased by 27%, to 5.13 ± 0.02 mΩ m² for acclimation at 20 Ω, 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.