Distribution of relaxation times analysis of rotating disk electrode impedance spectra
Alexander Rampf, Carla Marchfelder, Roswitha Zeis
Abstract
Distribution of relaxation times (DRT) is a valuable analytical tool to identify and quantify individual contributions in electrochemical impedance spectroscopy (EIS) data. This study introduces the DRT method for rotating disk electrode (RDE) measurements using the example of the oxygen reduction reaction (ORR) in alkaline media. A comprehensive peak assignment is presented based on the variation of different parameters, such as the oxygen saturation level in the electrolyte, the rotation rate, and the current density. Two prominent peaks in the low-frequency area are attributed to the oxygen mass transport and the charge transfer of the ORR. Additionally, three minor high-frequency peaks are identified. This assignment may serve as a reference for other researchers who intend to employ DRT for the RDE, regardless of the investigated reaction. Furthermore, a direct correlation between the Koutecký-Levich evaluation and the DRT analysis is demonstrated, indicating that DRT can be used similarly to the Koutecký-Levich analysis to extract kinetic information. This enables the possibility of performing and evaluating long-term in-situ steady-state measurements where the conventional Koutecký-Levich analysis is not applicable.