A method for estimating the capacitance of cathodic biofilms in aerobic systems

Cathodic biofilms play a crucial role in microbial electrochemical systems. Their function as electron acceptors suggests potential applications in carbon sequestration, bioelectrochemical synthesis, and possibly other yet-to-be-discovered microbial technologies. To better understand their electrochemical behavior, it is essential to characterize the complete impedance response on commonly used electrodes, typically high-surface-area carbon fabric or felt. Electrochemical impedance spectroscopy (EIS) is most effective with high-quality electrodes, as it minimizes artifacts caused by suboptimal materials such as carbon fabric. However, no current method allows for reliable EIS analysis using suboptimal electrodes. We developed a method for analyzing the impedance response of aerobic cathodic biofilms grown on carbon fabric electrodes exhibiting catalytic (EC’) behavior. Our approach involves filtering impedance data based on the E 1/2 criterion, enabling equivalent circuit analysis across various electrode surface areas. The method's reliability was confirmed by demonstrating a linear relationship between conductance and steady-state current, as predicted by linearization around E 1/2 for EC’ systems. This new approach is expected to help researchers obtain consistent impedance data in suboptimal experimental conditions where the use of high-quality electrodes, such as glassy carbon, is impractical. • EIS analysis using suboptimal electrodes. • Biofilms exhibiting catalytic (EC’) behavior. • Linear relationship between conductance and steady-state current. • Consistent impedance data in suboptimal experimental conditions.