Reviewing the fundamentals of supercapacitors and the difficulties involving the analysis of the electrochemical findings obtained for porous electrode materials

After a brief presentation of the major aspects involving supercapacitors, their fundamental aspects were reviewed with special emphasis on recent advances accounting for the electric double layer models proposed for porous carbon-based electrodes containing electrochemically active sub-nanometer pores. Despite these important considerations, the main focus of this review is concerned with the major difficulties found in trying to interpret the electrochemical findings obtained for porous electrodes in the presence and absence of a pseudocapacitance (e.g., Faradaic process) due to presence of distributed and dispersion capacitance effects. In this sense, we present a comprehensive analysis concerned with the misuse of the classic electrochemical methods initially proposed for the study of ideally flat and/or spherical electrodes that are commonly adapted to evaluate the specific capacitance exhibited by porous electrodes. We critically discussed the main pitfalls arising from the incorrect interpretation of the electrochemical findings obtained in the time and frequency domains using different electrochemical characterization methods. For the sake of reuniting our better understanding of the electro-chemistry of porous electrodes used in supercapacitors, we investigated the most relevant and recent papers in the field. Finally, we highlight some specific electrochemical methodologies proposed for the study of porous electrodes and some guidelines to establish a laboratory protocol to collect the most relevant information about the supercapacitors are presented.