Chronoamperometry and linear sweep voltammetry reveals the adverse impact of high carbonate buffer concentrations on anode performance in microbial fuel cells

Anode performance in microbial fuel cell (MFC) is usually examined by monitoring anode potentials in whole-cell polarization tests. However, this method does not fully test anode capabilities at higher current densities. To determine maximum anode current densities over a range of carbonate buffer (CB) concentrations we examined electrode performance using chronoamperometry, linear sweep voltammetry (LSV), and electrode potentials during polarization tests. Maximum anode current densities using chronoamperometry at +200 mV reached 42 ± 1 A m⁻² in 200 mM CB, with lower current densities using 300, 400 mM, or 50 mM CB, consistent with anode LSV data. However, upper current densities were limited to <25 A m⁻² when analyzed using polarization data due to solution and cathode resistances limiting higher current densities. The maximum power density of 3270 ± 50 mW m⁻² in 200 mM CB was similar to that obtained with higher buffer concentrations, incorrectly suggesting no adverse impact of higher CB concentrations on anode performance. Analysis using the electrode potential slope (EPS) method showed a clear and measurable unfavorable impact of higher CB concentrations on anode resistances. These results demonstrate that impacts of solution chemistry on anode performance could require current densities higher than those possible using polarization data.