Relative Resiliency of Bioanode Electrochemical Resistances with Changes in Interelectrode Spacing in Microbial Electrolysis Cells

Bioelectrochemical systems, such as microbial electrolysis cells (MECs), are more complex systems than abiotic electrochemical cells, as their performance can be impacted by microorganisms on the anode resulting from differences in materials (electrodes) and architectures (electrode spacing). Using the electrode potential slope (EPS) method, we quantified impacts on performance due to anode type (graphite brush or flat carbon felt) and changes in electrode spacing in MECs in terms of anode resistance separately from cathode resistance, anolyte and catholyte solution resistances, and total internal resistance. Carbon‐felt anodes had resistances (41–49 mΩ m ² ) substantially higher than those of brushes (11–14 mΩ m ² ), demonstrating the importance of the anode materials on performance. Both brush and felt anode resistances were unaffected by changes in spacing (and thus changes in solution resistances) when these anodes were moved further (2 cm) away from the cathode. This lack of a change with electrode location indicated stable performance of the exoelectrogenic microorganisms on the anodes despite the lower current densities due to increased solution resistances. These results show that large changes in MEC performance result from electrode materials but not from changes in current densities resulting from increased internal resistances due to larger electrode spacing.