Changes in electrode resistances and limiting currents as a function of microbial electrolysis cell reactor configurations

Abstract

Quantifying the resistances that different components of microbial electrolysis cells (MECs) contribute to the total internal resistance is important for understanding how different reactor configurations affect overall performance. The impact of the reactor architecture was examined here by varying the relative sizes of the electrodes and quantifying the changes in resistances of the electrodes and limiting current densities as a function of the applied potential (Eap). The MECs with equal cathode:anode size ratios (SR=1), showed a steady increase in current up to 1.8 mA for Eap’s ≤ 0.9 V. However, lower limiting currents were obtained for configurations with smaller anodes as shown by a lack of an increase in current for Eap > 0.7 V (limiting current of 0.8 mA, SR=16, and 1.0 mA, SR=4). The largest component of the internal resistance changed with the relative sizes of the electrodes. For example, the cathode resistance was 58% of the internal resistance for the configuration of SR=1 and 51% for SR=2, but the anode was 57% of the internal resistance for SR=16. These results show how differences in reactor architectures can be quantified in terms of individual electrode resistances and limiting currents using polarization data obtained by varying the applied potentials.