Spectroscopy electrochemical impedance

An electrochemical cell can be modeled by some common circuit elements corresponding to the electrical response of certain structures at or near the interface. In one particularly useful model, shown in Fig. 11a. a resistor is in series 

If instead of a direct potential an alternating (i.e., sinusoidal) signal is applied to the model electrode circuit in Fig. II a, the complex impedance can be measured. The impedance Z is the quotient of E and /  

The reversible electrochemical process is characterized by the following features  

The peak position does not change with the scan rate. 

Peak separation between the cathodic peak potential and the anodic potential (AEp) is a constant given by the following equation  

The thermodynamic potential of the redox reaction can also be obtained by averaging the anodic peak potential and the cathodic peak potential. However, for a reversible system, kinetic parameters such as reaction rate cannot be obtained because the reaction rates for both forward and backward reactions are extremely fast. 

For an irreversible system (O + e — R), the peak current is reduced and given by the following equation  

Electrochemical impedance spectroscopy techniques record impedance data as a function of the frequency of an applied signal at a fixed potential. A large frequency range (65 kHz-1 mHz) must be investigated to obtain a complete impedance spectrum. Dowling et al. and Franklin et al. demonstrated that the small signals required for EIS do not adversely affect the numbers, viability, and activity of microorganisms within a biofilm. EIS data may be used to determine the inverse of the corrosion 

The effects of different primers (metallic zinc, aluminum, and phosphate) over steel and an additional polyurethane topcoat over an epoxy 

Electrochemical impedance spectroscopy (EIS) provides indirect information about the surface phenomena of all kinds of electrodes [32]. The high-frequency part of impedance spectra of electrodes is usually attributed to surface phenomena such as Li-ion migration through surface films, surface film capacitance, and interfacial charge transfer [33]. However, it should be noted that EES provides very ambiguous information. A special skill, as well as experience, is needed for a reliable assignment of spectral features to the time constants of a complicated electrochentical system such as that of composite electrodes [34]. 

Before measuring the active mass itself and the composite electrodes, the intrinsic surface chemistry related to the Al CC, carbon black, and the chosen electrolyte solution can be measured by polarizing Al foil electrodes to high potentials, following ex situ measurements by surface-sensitive techniques (FTIR, Raman, XPS). In fact, the intrinsic surface chemistry of Al/solution systems can be measured in situ by FTIR and Raman spectroscopic methods. In order to understand the surface chemistry of composite cathodes, the following experimental steps are recommended  

Pristine particles of the active mass of interest should be stored at several temperatures (e.g., 30 °C, 60 °C) in the chosen electrolyte solutions. The solntion 

It is recommended to prepare electrodes comprising only A1 foil and the active mass— particles embedded by light pressnre into soft A1 foil electrodes. Such electrodes can be polarized, cycled, and then measnred by FTIR spectroscopy (reflectance modes such as grazing angle reflectance or specular reflectance modes in which there are commercial accessories available), Raman, and XPS. 

Finally, composite electrodes can be measnred after cycling. Particles scraped from cycled electrodes can be measnred by FTIR spectroscopy (diffuse reflectance mode), Raman, XPS, and high-resolntion electron microscopy. Changes in the surface chemistry due to cycling, aging, and different temperatures can be measured by impedance spectroscopy. 

Electrochemical impedance spectroscopy (EIS) is also commonly employed for analysis of enzymatic electrode systems [11], EIS is performed by overlaying a range of alternating current (AC) perturbation signals to an electrode that is under direct current (DC) bias. A Nyquist plot is then generated, and variations of the frequency response can then be used to interpret limiting mechanisms associated with charge transfer. 

This section aims to present the basics of electrochemical impedance spectroscopy (EIS) and to give some example of application in the electrochemical energy storage area. For more detailed information about this technique, the reader can refer to more specific works [10-13]. 

FIGURE 1.16 Evolution of 1/i on 30% platinized carbon plus polymer versus the reciprocal of the square root of the rotation speed (sample with 25% Nafion). (From Ayad, A., et al., J. Power Sources, 149, 66, 2005.) 

Although simple impedance measurement can tell the existence of an anodic film, electrochemical impedance spectroscopy (EIS) can obtain more information about the electrochemical processes. In general, the anode/electrolyte interface consists of an anodic film (under mass transport limited conditions) and a diffuse mobile layer (anion concentrated), as illustrated in Fig. 10.13a. The anodic film can be a salt film or a cation (e.g., Cu ) concentrated layer. The two layers double layer) behave like a capacitor under AC electric field. The diffuse mobile layer can move toward or away from anode depending on the characteristics of the anode potential. The electrical behavior of the anode/electrolyte interface structure can be characterized by an equivalent circuit as shown in Fig. 10.13. Impedance of the circuit may be expressed as 

FIGURE 10.13 Illustration (a) and equivalent circuit (b) of an anode/electrolyte interface structure. 

If a monochromatic alternating voltage U (t) = Um sin (cot) is applied to an electrode then the resulting current is I (t) = Im sin (cot -- ) where is the phase difference between the voltage and the current and Um and /m are the amplitudes of the sinusoidal voltage and current, respectively. Then the impedance is defined as 

Now let us sum up the following definitions resistance Zf (also R), reactance Z (also X), magnitude of impedance Z, conductance Y (also G), susceptance Y (also B), quality factor Q = z /Z = y /I , dissipation factor D = l/Q = tan5, loss angle 8. 

Frequently used procedures in modelling include the conversion of a parallel circuit to a series one and the conversion of a series circuit to a parallel one. 

The series circuit and the parallel circuit must be electrically equivalent. This means the dissipation factors tan 5 must be the same and the absolute values Z = 

The following equations enable these procedures to be performed [1]  

EIS is an efficient electrochemical technique for studying a variety of chemical, electrochemical, and surface reactions. This technique is used due to the ability of the method to give information on both the bulk and the interfacial properties of polymer-coated electrodes. EIS is the technique which is measuring impedance (complex 

Many membrane proteins are electrogenic, that is, translocate a net charge across a membrane. Consequently, it is possible to monitor their function directly by measuring the current flowing along an external electrical circuit upon their activahon. The techniques of choice for these measurements are EIS and potenhal-step chronoamperometry or chronocoulometry, because the limited volume of the ionic reservoir created by a hydrophilic spacer in solid-supported biomimetic membranes cannot sustain a steady-state current. 

A plot that has been frequently adopted in the literature to display an impedance spectrum as rich in features as the M plot is the Y /ft) versus Y /wplot, sometimes called a Cole-Cole plot [3-5]. Here Y and Y are the in-phase and quadrature component of the electrode admittance. However, it can be shown that this plot yields a semicircle for a series combination of a resistance and a capacitance, and 

FIGURE 1.8 CV for a PIGE modified with a microheterogeneous deposit of zeolite Y. Potential scan rate, 50 mV/sec. 

Electrochemical cells can be represented via an equivalent circuit formed by an association of impedances that pass current with the same amplitude and phase angle of the real cell under a given potential input. Thus, for a series RC circuit, the impedance and the phase angle are given by  

EIS is the experimental technique based on the measurement, under equilibrium or steady-state conditions, of the complex impedance of the cell at different frequencies of an imposed sinusoidal potential of small amplitude. As a result, a record of the variation of impedance with frequency (impedance spectrum) is obtained. Typically, EIS experiments are conducted from millihertz to kilohertz, so that available information covers a wide range of timescales (Retter and Lohse, 2005). 

For this equivalent circuit, the Nyquist plot provides a circumference arc with a maximum of imaginary impedance located at O),, , = The variation of the total 

For properly describing electrochemical processes, additional impedance elements have been introduced. The Warburg impedance (Raistrick and Huggins, 1982 Honders and Broers, 1985) is representative of diffusive constraints, being defined, for the case of linear diffusion, as a frequency-dependent impedance given by  

ASTM G106 describes a method to check the equipment and technique for collecting and presenting EIS data [16]. Type 430 stainless steel is to be tested in 0.005 M H2SO4-f 0.495 M Na2S04. A 10-mV amplitude signal is applied at the corrosion potential at 8-10 steps per decade from 10 000 to 0.1 Hz. The results of round-robin testing are provided. 

For a linear system, the current response will be a sine wave of the same frequency as the excitation signal, but shifted in phase. Since the impedance is the ratio of two sine waves, it is a complex number that can be represented by an amplitude and a phase shift or as the sum of real and imaginary components, Z(co) = Z ( )) + jZ (co). 

Complete commercial systems including both hardware and software allow EIS measurements and data analysis to be made rather easily. However, some care should be taken when using this approach, since the generation of artifacts and the misinterpretation of data are possible. A 

For the data in Fig. 6, the ohmic and polarization resistances can be determined to be about 0.3 and just under 100 cm, respectively. The value of Rp is slightly higher than that determined by linear polarization (Fig. 4) in a measurement that just preceded the EIS experiment on the same electrode. The double layer capacitance is seen to be 1/3000 SI cm = 333 pF cm . The polarization resistance determined by EIS can be used to determine the corrosion rate with the Stern-Geary equation, just as was described above for polarization resistance determined by linear polarization. EIS data provide no estimation of the Tafel slopes, which are required in the Stem-Geary equation. 

The other common plot for impedance data in corrosion is the complex plane plot or Nyquist plot, in which the imaginary component is plotted as a function of the real component at each frequency. The data from Fig. 6 are plotted in Fig. 7 in 

The simplest on-chip circuit that can be conceived is for differential OCP measurement, although complex electrostatic discharge protection needs to be incorporated. 

Many standard electrochemical techniques can be used, depending on the biological system to be studied. In the presence of redox markers in solution, modification of the electrode resulting from biomolecular interaction affects the impedance of the system, which can be measured by using electrochemical impedance spectroscopy (ElS). EIS is a very promising technique, in particular for the detection of DNA hybridization. 

In EIS, the impedance of the system is measured by applying a small ac signal and by the frequency scanned (typically between 10-100 kHz and 1 Hz or less). Stable impedance spectra can be obtained with electrically charged redox markers in solution. The data can be fitted with an equivalent electrical circuit, where the most important components are the charge transfer resistance Ret and the double layer/biolayer capacitance Cdi. 

On the other hand, a change in capacitance is expected upon biomolecular interactions. When a large target biomolecule interacts with the immobilized probe, the biolayer thickness increases, causing a decrease in the total capacitance of the S5 em. 

The maximum percentage change of charge transfer resistance upon hybridization with fully complementary target oligonucleotides was obtained with samples prepared by co-immobilization of oligonucleotide probes and mercaptohexanol with a DNA mole fraction of 20%. This corresponds to a mean probe surface density of 5.4 X 10 cm .  

The reader will note that there has been a steady increase in the level of sophistication of the PDM, with the introduction of barrier layer dissolution, and the relaxation therein, interstitial cations, hydride barrier layers, and bilayer structures. Current work in the author s laboratory is focused on extending the PDM to consider vacancies in the substrate metal and their annihilation on grain boundaries, precipitates, and dislocations, and the incorporation of the porous outer layer in oxide/oxide bilayer structures. 

All interfacial reactions that result in a change in oxidation state contribute to the total current density, which is written as 

Reference Defects Considered Character of Interfacial Reactions Relaxations Comments 

Chao et al. [1982] Stainless steel. Cation vacancies + anion vacancies Equilibrium, no dissolution of the barrier layer Concentrations of cation and anion vacancies Successfully accounted for phase angle 7t/4. 

Macdonald and Nickel. Cation vacancies Reversible reactions with Concentrations of cation and Demonstrated the importance 

Samin Sharifi-Asl and Digby D. Macdonald University of California at Berkeley, Departments of Materials Science and Engineering and 

Martin Fleischmann was an electrochemical impresario, who conducted his exploration of the subject with all of the skill and knowledge of a master symphony maestro. His many, impressive accomplishments are cataloged in this book and in the scientific literature, and serve as a beacon for those who follow in his footsteps. Although Martin did not use impedance methods extensively in his own work, he did use electrochemical impedance spectroscopy (EIS) to explore electrochemical processes at electrodes of different geometries [1,2]. However, it was his masterful treatment of electrochemical reaction mechanisms that forges the link between Martin s work and that of others who seek to define reaction mechanisms using impedance techniques. 

In this chapter, the point defect model (PDM), describing the formation and breakdown of passive films, is reviewed and developed. It is shown how important model parameters can be extracted from experimental impedance data and used to calculate the steady-state barrier layer thickness and passive current density as a function of voltage. In particular, the model is used to define the mechanism of the formation of CU2S on Cu in sulfide-containing brine. The present studies were conducted to provide a scientific basis for estimating the lifetimes of copper canisters in crystalline rock repositories in Sweden for the disposal of high level nuclear waste (HLNW). 

Developments in Electrochemistry Science Inspired by Martin Fleischmann, First Edition. Edited by Derek Fletcher, Zhong-Qun Xian and David E. Williams. 

Departamento de Quimica AnaUtica, Facultad de Ciencias Qutmica, Universidad Complutense de Madrid, Complutense de Madrid, Avda. Complutense, 28040, Madrid, Spain 

The wholesomeness of food is the real proviso for healthy life. Food freed from microbial and chemical cross-contaminations adds on to its hygienic and nutritive value. Infectious diseases spreading every day through food have become a life-threatening problem for millions of people around the world. In fact, food or food products are the potent transmitting agent of more than 250 known diseases [1]. 

EIS is a powerful electrochemical technique capable of detecting small changes occurring at the solution-electrode interface. Accordingly, EIS has been extensively exploited for 

Edited by Alberto Escarpa, Marfa Cristina Gonzdlez and Miguel Angel Ldpez. 2015 John Wiley Sons, Ltd. Published 2015 by John Wiley Sons, Ltd. 

For impedance measurements, a small sinusoidal AC voltage of small amplitude (typically 5-10 mV) is applied, and the current response, that differs in amplitude and phase (phase difference, 0) with the applied voltage, is determined. The impedance is calculated as the ratio between them [9]. 

It is well known that electrical resistance is the ability of a circuit element to resist the flow of electrical current. For a flow of DC current i to an applied DC potential E, the resistance is given by Ohm s law as 

However, in the real world, circuit elements exhibit much more complex behavior the simple concept of resistance cannot be used and in its place, impedance, a more general circuit parameter, is used. Like resistance, imp ance is the ability of the system to impede the flow of electrical current through it. Though it is similar to resistance, impedance is not time independent it is a time- or frequency-dependent parameter. Similar to resistance, impedance is defined as the ratio of the time-dependent current to the time-dependent potential. 

Electrochemical impedance is usually measured by applying an AC potential to an electrochemical cell and then measuring the current through the cell (Barsoukov and Macdonald, 2005, Ivers-Tiff et al., 2003, Orazem and Tribollet, 2008, Springer et al., 1996). The response to this potential is an AC current signal. According to ASTM G-15, the definition of electrochemical impedance is the frequency-dependent, complex valued proportionality factor, AE/Ai, between the applied potential (or current) and the response cmrent (or) potential in an electrochemical cell. This factor becomes the impedance when the perturbation and response are related linearly (the factor value is independent of the perturbation magnitude) and the response is caused only by the perturbation. 

A DC voltage results in current i showing system resistance R, whereas a sinusoidal potential results in a sinusoidal current showing system impedance. 

For a linear system, the current response is shifted in phase (( )) and has a different amplitude, /q, given as 

Definitions, Basic Relations, the Kramers-Kronig Transforms 

SEI layer during extended cycling as shown in Figs. 1.25 and 1.27. 

Impedance measurements for Si nanotubes with SiO constraining iayer. Reprinted with permission from Ref 109. Copyright 2012, Nature Pubiishing Group. 

These results, along with the galvanostatic cycling results shown in Fig. 1.28, highlight the importance of SEI growth and control for achieving Si electrodes with good capacity retention. 

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Other techniques to detennine the corrosion rate use instead of DC biasing, an AC approach (electrochemical impedance spectroscopy). From the impedance spectra, the polarization resistance (R ) of the system can be detennined. The polarization resistance is indirectly proportional to j. An advantage of an AC method is given by the fact that a small AC amplitude applied to a sample at the corrosion potential essentially does not remove the system from equilibrium. 

Electrochemical Impedance Spectroscopy (EIS) and AC Impedance Many direct-current test techniques assess the overall corrosion process occurring at a metal surface, but treat the metal/ solution interface as if it were a pure resistor. Problems of accuracy and reproducibility frequently encountered in the application of direct-current methods have led to increasing use of electrochemical impedance spectroscopy (EIS). 

Although the above experiments involved exposure to the environment of unbonded surfaees, the same proeess oeeurs for buried interfaces within an adhesive bond. This was first demonstrated by using electrochemical impedance spectroscopy (EIS) on an adhesive-covered FPL aluminum adherend immersed in hot water for several months [46]. EIS, which is commonly used to study paint degradation and substrate corrosion [47,48], showed absorption of moisture by the epoxy adhesive and subsequent hydration of the underlying aluminum oxide after 100 days (Fig. 10). After 175 days, aluminum hydroxide had erupted through the adhesive. 

Electrical characteristics of surface films formed electrochemically can be analysed using frequency response analysis (FRA) (sometimes called electrochemical impedance spectroscopy, or This technique is... 

The capacitance. The electrical double layer may be regarded as a resistance and capacitance in parallel see Section 20.1), and measurements of the electrical impedance by the imposition of an alternating potential of known frequency can provide information on the nature of a surface. Electrochemical impedance spectroscopy is now well established as a powerful technique for investigating electrochemical and corrosion systems. 

The method is referred to as electrochemical impedance spectroscopy (EIS), by Mansfield... 

Electrochemical Impedance Spectroscopy see Frequency Response Analysis. 

Frequency Response Analysis the response of an electrode to an imposed alternating voltage or current sign of small amplitude, measured as a function of the frequency of the perturbation. Also called Electrochemical Impedance Spectroscopy. 

Electrochemical impedance spectroscopy (EIS) in a sufficiently broad frequency range is a method well suited for the determination of equilibrium and kinetic parameters (faradaic or nonfaradaic) at a given applied potential.268,269 EIS has been used to study polycrystalline Au, Cd, Ag, Bi, Sb, and other electrodes.152249 270-273... 

Electrochemical impedance spectroscopy leads to information on surface states and representative circuits of electrode/electrolyte interfaces. Here, the measurement technique involves potential modulation and the detection of phase shifts with respect to the generated current. The driving force in a microwave measurement is the microwave power, which is proportional to E2 (E = electrical microwave field). Therefore, for a microwave impedance measurement, the microwave power P has to be modulated to observe a phase shift with respect to the flux, the transmitted or reflected microwave power APIP. Phase-sensitive microwave conductivity (impedance) measurements, again provided that a reliable theory is available for combining them with an electrochemical impedance measurement, should lead to information on the kinetics of surface states and defects and the polarizability of surface states, and may lead to more reliable information on real representative circuits of electrodes. We suspect that representative electrical circuits for electrode/electrolyte interfaces may become directly determinable by combining phase-sensitive electrical and microwave conductivity measurements. However, up to now, in this early stage of development of microwave electrochemistry, only comparatively simple measurements can be evaluated. 

Papakonstantinou, P., Zhao, J. F., Richardot, A., McAdams, E. T., and McLaughlin, J. A., Evaluation of Corrosion Performance of Ultra-thin Si-DLC Overcoats with Electrochemical Impedance Spectroscopy, Diamond Relat. Mater, Vol. 11,... 

The UPD and anodic oxidation of Pb monolayers on tellurium was investigated also in acidic aqueous solutions of Pb(II) cations and various concentrations of halides (iodide, bromide, and chloride) [103]. The Te substrate was a 0.5 xm film electrodeposited in a previous step on polycrystalline Au from an acidic Te02 solution. Particular information on the time-frequency-potential variance of the electrochemical process was obtained by potentiodynamic electrochemical impedance spectroscopy (PDEIS), as it was difficult to apply stationary techniques for accurate characterization, due to a tendency to chemical interaction between the Pb adatoms and the substrate on a time scale of minutes. The impedance... 

Ragoisha GA, Bondarenko AS, Osipovich NP, Streltsov EA (2004) Potentiodynamic electrochemical impedance spectroscopy Lead underpotential deposition on tellurium. 1... 

ENA was recently used for remote on-line corrosion monitoring of carbon steel electrodes in a test loop of a surge water tank at a gas storage field. An experimental design and system for remote ENA and collection of electrochemical impedance spectroscopy (EIS) data (Fig. 13) have been presented elsewhere. In the gas storage field, noise measurements were compared with electrode weight loss measurements. Noise resistance (R ) was defined as... 

Electrochemical impedance spectroscopy, AC probes. EIS, although around since the 1960s, has primarily been a laboratory technique. Commercially available probes and monitoring systems that measure EIS are becoming more widely used, especially in plants that have on-staff corrosion experts to interpret the data or to train plant personnel to do so. 

Electrochemical impedance, weight loss, and potentiodyne techniques can be used to determine the corrosion rates of carbon steel and the activities of both sulfate-reducing bacteria and acid-producing bacteria in a water injection field test. A study revealed that the corrosion rates determined by the potentiodyne technique did not correlate with the bacterial activity, but those obtained by electrochemical impedance spectroscopy (EIS) were comparable with the rates obtained by weight loss measurements [545]. 

Makharia R, Mathias ME, Baker DR. 2005. Measurement of catalyst layer electrolyte resistance in PEECs using electrochemical impedance spectroscopy. J Electrochem Soc 152 A970-A977. 

Itagaki, M. Fukushima, H. Inoue, H. Watanabe, K. Electrochemical impedance spectroscopy study on the solvent extraction mechanism of Ni(II) at the water 1,2-dichloroethane interface. J. Electroanal. Chem. 2001, 504, 96-103. 

In this paper we present results from independent studies on the stage 2 to stage 1 transition area that show some unexpected features (anomalies). The results are obtained by electrochemical impedance spectroscopy (EIS), entropy measurements (AS(x)) and in situ x-ray diffractometry (XRD). The aim is to understand the mechanism of stage transition dealing with the observed anomalies. 

Examination of the membranes with a variety of physicochemical techniques, from related electrochemical approaches (as electrochemical impedance spectroscopy (EIS), voltammetry and chronoamperometry) to more sophisticated characterization methods (spectroscopy and microscopy), actually serves the same end as the theory and leads to a deeper understanding of the chemistry behind the functioning of these sensors [5, 6],... 

C.M. Ruan, L. Yang, and Y. Li, Immunobiosensor chips for detection of Escherichia coliO 51 Wl using electrochemical impedance spectroscopy. Anal. Chem. 74, 4814-4820 (2002). 

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