The electrochemical impedance spectra (EIS) of nonlinear and unstable electrochemical systems are numerically simulated. The effects of linear and exponential potential drifts on the EIS of anodic dissolution are examined. For direct dissolution, the numerical results are compared with the analytical solutions. For the case of dissolution via an adsorbed intermediate, Langmuir and Frumkin adsorption isotherms are considered. The simulated spectra are subjected to Kramers Kronig Transform (KKT). KKT is found to be effective in revealing the inconsistencies in the impedance spectra of unstable systems, even though it does not always flag the nonlinearities. It is shown that if the data were to be analyzed without validation by KKT, it can lead to incorrect choice of reaction mechanism or equivalent circuits. © 2010 Elsevier Ltd.

Srinivasan Ramanathan

Department Of Chemical Engineering

ADSORBED INTERMEDIATES

Analytical solutions

Anodic dissolution

ELECTROCHEMICAL IMPEDANCE SPECTRA

Electrochemical systems

FRUMKIN ADSORPTION ISOTHERMS

Impedance spectrum

KRAMERS KRONIG TRANSFORMS

Langmuirs

Non-Linearity

Numerical results

POTENTIAL DRIFT

reaction mechanism

SIMULATED SPECTRA

Unstable system

Adsorption

Electrochemical corrosion

Electrochemistry

Equivalent circuits

Mathematical transformations

Solid solutions

dissolution

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IIT Madras

Electrochimica Acta

The effect of instabilities on the nonlinear electrochemical impedance spectroscopic (NLEIS) response of a simple electron transfer reaction in a kinetic and diffusion-controlled regime was studied using classical Fe2+/Fe3+ redox couple on a gold electrode. Numerical simulations were employed to calculate the NLEIS response, and the predictions were compared with experimentally acquired NLEIS data. Instabilities were introduced by continuously changing the dc potential or the active species concentrations. At high frequencies, the effect of potential instabilities manifested more clearly in higher harmonic signals than at the fundamental frequency. In case of changes in species concentrations which did not break the symmetry, the higher harmonics were not particularly more sensitive than the fundamental. An analysis of the results shows that multiple factors contribute to the higher harmonics. The sensitivity of second harmonics to the instabilities arises from the nonlinear component of the rate constant as well as the interaction between the rate constant oscillations and concentration oscillations at the applied frequency. The results show that NLEIS can be used to quickly identify instabilities which alter the symmetry. © The Author(s) 2019.

Journal of the Electrochemical Society

Analysis of instabilities in electrochemical systems using nonlinear electrochemical impedance spectroscopy

Concretes with fly ash, slag, limestone calcined clay, etc. exhibiting high resistivity are being used to enhance the chloride resistance of structures – to achieve durability. Prior to use, the engineers need to determine the chloride threshold (Cl th ) of such highly resistive steel cementitious (S-C) systems (a key parameter to estimate service life). Most Cl th tests involve repeated measurements of polarization resistance (R p ) and detection of corrosion initiation of steel embedded in hardened cementitious system (a sol-gel structure with partially filled pores). The high resistivity of such systems should be considered while interpreting the electrochemical response to determine R p . This paper experimentally evaluates the suitability of LPR and EIS techniques for assessing R p of steel embedded in highly resistive systems. Experiments were conducted with lollipop type specimens (steel reinforcement embedded in mortar cylinders). The following three types of mortar having various resistivities were prepared: (i) ordinary portland cement (OPC), (ii) OPC + fly ash, and (iii) limestone calcined clay cement. Experimental observations on how the following three factors affect the electrochemical response in highly resistive S-C systems are provided: (i) resistivity of concrete covering the embedded steel, (ii) electrode configuration, and (iii) electrochemical test parameters. It was found that electrochemical impedance spectroscopy (EIS) can detect corrosion initiation in highly resistive systems at earlier stages than the linear polarization resistance (LPR) technique. Also, the guidelines on how to use EIS technique to determine the R p of steel embedded in highly resistive S-C systems are provided. © 2019 Elsevier Ltd

Investigation on the polarization resistance of steel embedded in highly resistive cementitious systems – An attempt and challenges

Nonlinear Electrochemical Impedance Spectroscopy (NLEIS) is a method of characterizing an electrochemical systems by applying a large amplitude sinusoidal perturbation signal. This article presents a comprehensive review of existing literature on NLEIS analysis development and applications. Two types of NLEIS reports available in the literature, viz. one in which only the fundamental impedance is studied and the other in which both the fundamental and higher harmonic responses are analyzed, are reviewed. Early reports on the development of NLEIS methodology are compiled. Recent advances in the application of NLEIS, in particular in the area of fuel cells, are summarized. In addition, applications of related techniques such as total harmonic distortion and Volterra kernel are included in the purview of this article. There is a large scope for applying NLEIS to understand electrochemical processes. The roadblocks that need to be overcome to enable wider application of NLEIS are identified, and directions for further research are suggested. © The Author(s) 2017. Published by ECS. All rights reserved.

Review - Nonlinear electrochemical impedance spectroscopy

The impedance spectral response of electrochemical systems to multi sine (MS) potential perturbations was simulated using numerical techniques. The MS waves comprised of odd harmonic waves and were applied to a simple electron transfer reaction, and a reaction with an adsorbed intermediate. The governing equations were solved without linearization. Two choices of frequency sets with phases corresponding to the minimum crest factor were employed. The effects of large amplitude perturbations, potential instability, noise and solution resistance were investigated. The EIS data were subjected to Kramers Kronig transforms (KKT). The results show that (i) if large amplitude perturbations are used, the spectra acquired using MS appear to be noisy and they violate KKT, (ii) potential drifts and noise effects are successfully identified by KKT and (iii) in the presence of a significant solution resistance, the kinetic equations must be employed along with the equivalent circuit model to estimate the kinetic parameters. © The Electrochemical Society.

ECS Transactions

Multi-sine EIS-drift, non linearity and solution resistance effects

The effect of solution resistance on the nonlinear electrochemical impedance spectra under quasi-potentiostatic conditions was investigated by numerical simulations. An electron transfer reaction, a reaction with an adsorbed intermediate and a reaction exhibiting negative resistance were chosen as the candidates and large amplitude perturbations were employed. The potential across the interface drifts initially and stabilizes after a certain time, which depends on the solution resistance and the kinetic parameter values. The fraction of the applied potential drop occurring across the metal-solution interface depends on the frequency and the amplitude of the perturbation as well as the value of solution resistance. This in turn leads to the possibility that, for a given conditions, a part of the spectrummay be acquired in the linear regime while the remaining part may be acquired in the nonlinear regime. The sensitivity of the Kramers Kronig transform (KKT) to identify these cases is evaluated. The results show that although the spectra are distorted by poorly conducting solution, the sensitivity of KKT to identify the nonlinear effects is not enhanced by the introduction of significant solution resistance. © Springer-Verlag 2011.

Journal of Solid State Electrochemistry

Numerical investigations of solution resistance effects on nonlinear electrochemical impedance spectra

Electrochemical Impedance Spectroscopy (EIS) is a sensitive technique for determining the mechanistic pathway of an electrochemical reaction. In particular, the low frequency behavior of the impedance at various over-potentials can help differentiate between very similar mechanisms. Nine different mechanisms related to anodic dissolution of metals are simulated and the EIS patterns that are expected for these mechanisms are identified. This library of patterns reported here will help in eliminating certain mechanisms and identifying mechanisms with the least number of parameters that can be applied for modeling experimental EIS data. © 2009 Elsevier B.V. All rights reserved.

Fulltext

Journal of Electroanalytical Chemistry

Identification of reaction mechanism for anodic dissolution of metals using Electrochemical Impedance Spectroscopy

Journal of The Electrochemical Society

On the Sensitivity of the Kramers–Kronig Relations to Nonlinear Effects in Impedance Measurements

Israel Journal of Chemistry

On Selection of the Perturbation Amplitude Required to Avoid Nonlinear Effects in Impedance Measurements

Calculation of the rate constants of nickel electrodissolution in acid medium from EIS

Reflections on the history of electrochemical impedance spectroscopy

Effect of potential drifts and ac amplitude on the electrochemical impedance spectra

Journal	Electrochimica Acta
ISSN	00134686
Open Access	No