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Invited for this issue's Front Cover is the group of Professor Fabio La Mantia at the University of Bremen (Germany). The cover picture shows the developed theoretical variance of the error on the admittance and how this expression captures the experimental values of the standard deviations of the real and imaginary parts of the admittance. Read the full text of the Research Article at 10.1002/celc.202200109.

Different strategies can be used to acquire dynamic impedance spectra during a cyclic voltammetry experiment. The spectra are then analyzed by fitting them with a model using a weighted non‐linear least‐squares minimization algorithm. The choice of the weighting factors is not trivial and influences the value of the extracted parameters. At variance with the classic electrochemical impedance spectroscopy, dynamic impedance measurements are performed under non‐stationary conditions, making them typically more prone to errors arising from the voltage and current analog‐to‐digital conversion. Under the assumption that the noise in the voltage and current signals have a constant variance along the measurement and that it is uncorrelated between distinct samples, we calculate an expression for the expected variance of the error of the resulting immittances, which considers the specific procedure used to extract the spectra under the time‐varying nature of the measurements. The calculated variance of the error is then used as a rigorous way to evaluate the weighting factors of the least‐squares minimization, assuming that the fitted model is ideally exact and that there are no systematic errors. By exploring two classical electrochemical systems and fitting the measured spectra with a transfer function measurement model, namely with the Padé approximants, we show that the variance evaluated with our method captures the frequency dependence of the resulting residuals and can be used for reliably performing the complex non‐linear least‐squares fitting procedure.

The Front Cover shows the developed theoretical variance of the error on the admittance and how this expression captures the experimental values of the standard deviations of the real and imaginary parts of the admittance. More information can be found in the Research Article by R. Chukwu et al.