The Utility and Limitations of Distribution of Relaxation Times (DRT) Methods for Impedance Analysis

Distribution of Relaxation Times (DRT) models are gaining popularity among researchers employing electrochemical impedance spectroscopy, especially by those studying fuel cells. The main reason for this popularity is that DRT is deemed non-parametric, has a perceived ability to resolve processes with similar timescales, and is considered to provide a model-free description of impedance data. In this manuscript, we show that DRT results are strongly dependent on a user selected parameter and, because the DRT method assumes a specific model, the time constants obtained do not necessarily correlate with those associated with physical systems.