Application of the Mott-Schottky model to select potentials for EIS studies on electrodes for electrochemical charge storage

Electrochemical Impedance Spectroscopy (EIS) is a powerful technique to understand the electrode-electrolyte interaction and to evaluate degradation, resistive behaviour and electrochemical activity of energy storage materials used in batteries, pseudocapacitors and supercapacitors among others. However, it can sometimes be misused or under-interpreted. To effectively acquire EIS results, the voltages imposed to the working electrode at which EIS spectra are obtained, shall be critically selected. This work follows a previous study on the EIS response of Nickel-Cobalt hydroxide, and highlights how the Mott-Schottky model can be used as a complementary tool to explain EIS results obtained at different potentials. The Mott-Schottky model is used to understand further the fundamental processes occurring at the electrode-electrolyte interface of nickel-cobalt hydroxide in alkali media and to explain the changes in conductivity of the material that ultimately determine the electrode electrochemical activity. The applicability of the model to assist in the potential selection for EIS studies on other important charge storage materials such as MnOx and MoOx is discussed too.