The accurate use of impedance analysis for the study of microbial electrochemical systems

Abstract

The present critical review aims to portray the principles and theoretical foundations that have been used for the application of electrochemical impedance spectroscopy (EIS) to study electron-transfer mechanisms, mass transfer phenomena and distribution of the heterogeneous properties of microbial electrochemical systems (MXCs). Over the past eight years, the application of this method has allowed major breakthroughs, especially in the field of microbial fuel cells (MFCs); however, it is still most widely extended only to the calculation of internal resistances. The use and interpretation of EIS should greatly improve since the intrinsic knowledge of this field, and efforts and current trends in this field have already allowed its understanding based on rather meaningful physical properties and not only on fitting electrical analogues. From this perspective, the use, analysis and interpretation of EIS applied to the study of MXCs are critically examined. Together with the revision of more than 150 articles directly devoted to this topic, two examples of the correct and improved analysis of EIS data are extensively presented. The first one focuses on the use of graphical methods for improving EIS analysis and the other one concentrates on the elucidation of the constant phase element (CPE) parameters. CPEs have been introduced in equivalent circuit models, sometimes without solid justification or analysis; the effective capacitance has been obtained from CPE parameters, following an unsuitable theory for the case of microbial-electrochemical interfaces. The use of CPE is reviewed in terms of meaningful physical parameters, such as biofilm thickness. The use of a finite-diffusion element is reviewed throughout estimation of accurate values for obtaining the dimensionless numbers, Schmidt and Sherwood, in the context of a dioxygen-reducing-biocathode, under different flow-rate conditions. The use and analysis of EIS in this context are still emerging, but because of the promising potential of MXCs in renewable power generation, wastewater treatment and energy-positive biorefining, among other applications, it becomes necessary to boost our global capacities for the application of EIS-and especially its interpretation-so that we achieve a better understanding and optimization of these systems.

Nanocomposite SPEEK-based membranes for Direct Methanol Fuel Cells at intermediate temperatures

“…P exp = V exp · i and P mod = V mod · i. Since power density is very sensitive to the cell voltage (V 2 ) and a function of the ohmic resistance (R MEA ), see Equation (13), this property has been used for a refined determination of the model parameters and especially the ohmic resistance term [66]. In our case, we conceived a global mean square error factor composed of Σ(V exp -V mod ) 2 · Σ(P exp -P mod ) 2 which was minimized by iterative calculations using a commercial computer software package.…”

Analysis of bio-anode performance through electrochemical impedance spectroscopy

“…In a recent review article [3], the lack of EIS studies in terms of appropriate equivalent circuits that describe the physical-chemical parameters of MES, were addressed. In the same direction, we showed in a previous study and through a systematical experimental approach that the use of traditional models was leading to an underestimation of the diffusion parameter [5].…”

“…In order to analyze their behavior, several electrochemical tools are common in MES research [1], for example chronoamperic measurements to determine polarization curves, and Electrochemical Impedance Spectroscopy (EIS) to study the processes and reactions limiting MES performance [3][4][5].…”

Theoretical Modeling of the Possibility of Acid Producing Bacteria Causing Fast Pitting Biocorrosion

“…Direct update of electrons from an electrode has even seen applications in microbial electro-synthesis to produce useful chemicals using biofilms [14]. Various methods of electron transfer are also discussed extensively in the literature of microbial fuel cells [15], although in most cases, the electron transfer direction is from inside the anodic biofilm cells to the electrode outside with the exception of biocathodes [16]. Iron oxidation can also couple with water or proton reduction to produce H 2 (just as in chemical corrosion without biocatalysis of a biofilm).…”