Evaluation of electrode and solution area-based resistances enables quantitative comparisons of factors impacting microbial fuel cell performance

Abstract

Direct comparisons of microbial fuel cells (MFCs) based on maximum power densities are hindered by different reactor and electrode sizes, solution conductivities, and materials. We propose an alternative method here, the electrode potential slope (EPS) analysis, to enable quantitative comparisons based on anode and cathode area-based resistances and operating potentials. Using the EPS analysis, the brush anode resistance (RAn= 10.6 ± 0.5 mΩ m2) was shown to be 28% less than the resistance of a 70% porosity diffusion layer (70% DL) cathode (Rcat = 14.8 ± 0.9 mΩ m2), and 24% less than the solution resistance (RΩ = 14 mΩ m2) (acetate in 50 mM phosphate buffer solution). Using a less porous cathode (30% DL) did not impact the cathode resistance, but it reduced the cathode performance due to a lower operating potential. With low conductivity domestic wastewater (RΩ = 87 mΩ m2), both electrodes had higher resistances, with RAn = 75 ± 9 mΩ m2 and RCat = 54 ± 7 mΩ m2 (70% DL). Our analysis of the literature using the EPS analysis shows how electrode resistances can easily be quantified to compare system performance when the electrode distances are changed or the electrodes have different sizes.