Bioelectrochemical characterization of a biogas-producing microbial electrolysis cell (MEC): advantages and...

Electroanalytical techniques can be used to provide new insights into the electrochemical response of microbial bioelectrodes with some limitations due to complex interphase biofilm-electrode. In this work, characterization techniques, including open-circuit voltage, cyclic voltammetry, and electrochemical impedance spectroscopy, were applied to the bioanode, while chronoamperometry was used for the MEC with nine combinations of applied voltage and biomass content for anodic biogas production. The open-circuit potential was characteristic of the bioanode at -0.4 V ± 0.02 V vs. Ag/AgCl; the cumulative charge evolution allowed differentiation of operation conditions, reaching a total charge between 30C and 170C. Three distinct profiles were found among the voltammograms including oxidation peaks, oxidation waves and no faradaic signals. The charge transfer resistance estimated via electrochemical impedance spectroscopy only allowed differentiation of the final from the initial conditions. A nonlinear correlation was found between electrochemical parameters and biogas volume and its composition. This work presents a method for the systematic electroanalysis of bioelectrodes and provides information on their behavior under different biomass and applied voltage conditions.