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.

Srinivasan Ramanathan

Department Of Chemical Engineering

dissolution

Electrochemical corrosion

Metal analysis

Metal recovery

Anodic dissolution

Different mechanisms

Electrochemical reactions

LOW FREQUENCY BEHAVIOR

Mechanistic pathways

reaction mechanism

Sensitive techniques

Electrochemical impedance spectroscopy

Fulltext

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Electroanalytical Chemistry

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

The response of an electrochemical reacting system to potential perturbations during electrochemical impedance spectrum measurement is investigated using numerical simulation. Electrochemical metal dissolution via an adsorbed intermediate species is analyzed and it is shown that applying the potential perturbation causes the average surface coverage to drift. For high frequency perturbations, the final value of the average surface coverage depends mainly on the kinetic parameters and the amplitude of the applied perturbation. Acquiring the data during the first few cycles of perturbations leads to an incorrect calculation of the impedance, particularly for large amplitude perturbations. Repeating the experiments will not identify this drift, while Kramers-Kronig Transform (KKT) can successfully detect this problem. The correct experimental methodology to overcome this effect and obtain the impedance spectra is also described. Another reaction with two adsorbed intermediates is also investigated and it is shown that in certain cases, the violations of linearity criteria can also be detected by KKT. The results illustrate the importance of validating the impedance data with KKT before further analysis. © 2011 Elsevier Ltd. All rights reserved.

Electrochimica Acta

An analysis of drifts and nonlinearities in electrochemical impedance spectra

The dissolution of copper in solutions containing Glutamic acid and hydrogen peroxide is analyzed using EIS. Potentiodynamic polarization studies show that there is no strong passivating layer formed on the copper surface in solutions containing 0.5 wt% Glu and 0.1 vol% hydrogen peroxide. Electrochemical impedance spectra of copper in this solution at various overpotential were acquired and modeled using electrical equivalent circuit and reaction mechanism analysis. The results show that the reaction involves at least two adsorbed intermediates. ©The Electrochemical Society.

ECS Transactions

Analysis of copper dissolution in glutamic acid and hydrogen peroxide using EIS

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.

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

Anodic dissolution of copper in glycine solution at various hydrogen peroxide concentrations was investigated. The dissolution rate increases, reaches a maximum, and then decreases with hydrogen peroxide concentration. Anodic polarization studies and electrochemical impedance spectroscopy (EIS) studies were carried out to determine the mechanistic pathway of anodic dissolution of copper in glycine system at three different hydrogen peroxide concentrations: one at low hydrogen peroxide concentration in the active dissolution region, another in the maximum dissolution region, and the third at the high hydrogen peroxide concentration in the post-peak-dissolution region. The EIS data in complex plane plots show presence of two capacitance loops and one negative capacitance loop. The impedance plot patterns strongly depend on the hydrogen peroxide concentration in solution. Reaction mechanism analysis technique was employed to model the EIS data. A three-step mechanism with two intermediate adsorbates and a parallel dissolution by catalytic mechanism simulates EIS patterns which match the experimental trends. The intermediates are likely to be cupric and cuprous oxides. The essential features of impedance spectra at various overpotentials at three different hydrogen peroxide concentrations are captured by the proposed mechanism. The results also show that the film present on the copper surface in glycine and hydrogen peroxide solutions does not passivate the surface. © 2010 Springer-Verlag.

Journal	Data powered by TypesetJournal of Electroanalytical Chemistry
Publisher	Data powered by TypesetElsevier
ISSN	15726657
Open Access	Yes