Appropriate Use of Electrochemical Impedance Spectroscopy in Water Splitting Electrocatalysis

Abstract

Electrochemical impedance spectroscopy (EIS) is an efficient tool that reveals the electrochemical characteristics of catalysts, surfaces, interfaces, coatings, and so forth. Use of EIS in different areas of energy research wherever current, potential, and charge determine the performance has become inevitable. Electrocatalytic water splitting is one of such fields focused on generating high purity hydrogen, where EIS is used to correlate the activity trends measuring charge transfer resistances (R ct ). In doing so, different conventions are followed. A few perform EIS at the open circuit potential (OCP), a few perform at onset potential or at a potential before onset potential, a few perform at different potentials for different catalysts at which they deliver the same current density, and a large group of people choose a constant potential beyond onset, at which all the studied catalysts show appreciable catalytic activity. Existence of such different practices in using EIS to characterize water splitting electrocatalysts often lead to misinterpretation of the activity trends. Hence, to provide a clear view on the appropriate use of EIS in water splitting electrocatalysis, we have carried out a comparative EIS study on the oxygen evolution reaction (OER) activity trend of stainless steel 304 (SS-304), Co, Ni, and Cu foils in 1 M KOH at all the above-stated conditions and the results showed that the EIS carried out at constant potentials in the catalytic turnover region is appropriate.[a] Dr.

A Complementary Co−Ni Phosphide/Bimetallic Alloy‐Interspersed N‐Doped Graphene Electrocatalyst for Overall Alkaline Water Splitting

“…The estimated EIS parameters namely R s , R ct , and Q are the uncompensated resistance, charge‐transfer resistance, and constant phase element (CPE), respectively. The CPE often occurs in the modified electrodes or electrodes coated with catalyst material due to the high roughness factor [24] . Long‐term stability tests were performed using chronoamperometry at a current density of 15 mA cm −2 for the OER/HER studies.…”

A soft molecular 2Fe–2As precursor approach to the synthesis of nanostructured FeAs for efficient electrocatalytic water oxidation

“…68 The selected potential for EIS (E ¼ 1.51 V) provides considerable catalytic activity (>10 mA cm À2 ) for all the materials. 69 Fig. 3c shows the smallest charge transfer resistance (R ct ) across the electrolyte/electrode interface for FeAs compared to the reference Fe materials (for a detailed discussion see Fig.…”

Methods for the Determination of Valid Impedance Spectra in Non‐stationary Electrochemical Systems: Concepts and Techniques of Practical Importance

“…Electrochemical impedance spectroscopy (EIS) is a widely used, powerful tool for investigation of charge transfer and charge transport processes occurring in electrochemical systems. [1][2][3][4][5][6][7][8] The term "spectroscopy" in the name of the method is justified, since any study of how absorption of electromagnetic radiation depends on frequency can be considered as spectroscopy. A plot containing the intensity of the absorption, i. e., the electrochemical impedance, with respect to the frequency is called a "spectrum".…”