A comparative study of different electrochemical methods to determine cell internal parameters of microbial fuel cells

Abstract The efficient energy recovery from wastewater through microbial fuel cells (MFC) depends on a comprehensive understanding of the electrochemical properties of the system. Different methods to infer electrochemical parameters can be applied. However, the absence of studies confirming the compatibility and inter-validity of these methods makes their comparison difficult. In this study six different electrochemical methods were compared in triplicate MFCs: i) varying circuit resistance (VCR); ii) linear sweep voltammetry (LSV); iii) current interruption (CI); iv) electrochemical impedance spectroscopy (EIS); v) pulse width modulation (R-PWM); and vi) the perturbation observation (P/O) algorithm. Comparative investigations of the ohmic resistances from CI (73.0 ± 11.4 Ω), EIS (70.8 ± 11.1 Ω) and R-PWM (73.3 ± 11.2 Ω) showed high agreement. Further analysis of the activation resistances using detailed model-based methods, such as EIS (26.0 ± 10.9 Ω) and R-PWM (25.0 ± 3.0 Ω) demonstrated that both methods provide identical results. The applicability of the R-PWM mode as a real-time optimization method can be supported by the calculated maximum power densities from VCR and LSV together with the adjusted resistance from the P/O algorithm. In R-PWM mode theoretical power densities up to 95% of the maximum power point can be achieved.