Seven steps to reliable cyclic voltammetry measurements for the determination of double layer capacitance

Discovery of electrocatalytic materials for high-performance energy conversion and storage applications relies
on the adequate characterization of their intrinsic activity, which is currently hindered by the dearth of a protocol
for consistent and precise determination of double layer capacitance (CDL). Herein, we propose a seven-step
method that aims to determine CDL reliably by scan rate-dependent cyclic voltammetry that considers aspects
that strongly influence the outcome of the analysis, including (1) selection of a suitable measuring window, (2)
the uncompensated resistance, (3) optimization of measuring settings, (4) data acquisition, (5) selection of data
suitable for analysis, (6) extraction of the desired information, and (7) validation of the results. To illustrate the
proposed method, two systems were studied: a resistor-capacitor electric circuit and a glassy carbon disk in an
electrochemical cell. With these studies it is demonstrated that when any of the mentioned steps of the procedure
are neglected, substantial deviations of the results are observed with misestimations as large as 61% in the case
of the investigated electrochemical system. Moreover, we propose allometric regression as a more suitable model
than linear regression for the determination of CDL for both the ideal and the non-ideal systems investigated. We
stress the importance of assessing the accuracy of not only highly specialized electrochemical methods, but also
of those that are well-known and commonly used as it is the case of the voltammetric methods. The procedure
proposed herein is not limited to the determination of CDL, but can be effectively applied to any other analysis
that aims to deliver quantitative results via voltammetric methods, which is crucial for the study of kinetic and
diffusion phenomena in electrochemical systems.