Dynamic Electrochemical Impedance Spectroscopy

Sacci and Harrington [133] recently developed hardware and software for DEIS. They typically used 34 frequency numbers 1, 3, 5, 7, 9, 11, 13, 17, 21, 25, 31, 37, 44, 52, 64, 75, 90, 100, 110, 130, 170, 210, 250, 310, 370,440, 520, 640, 750, 900, 1000, 1100, 1300, and 1700, that is, the smallest frequency chosen was multiplied by these numbers to obtain real frequencies. The data were sampled continually during the potential sweep, and the FFT was performed on blocks of 4,096 (or 2,024) points. A schema of a DEIS system, based on the Keithley KUSB3116 

FT-EIS allows for measurements of nonstationary systems evolving slowly with time or during a potential sweep. In addition, it allows for detecting and quantifying the presence of time variance and nonlinear distortions in experimental data [123-127, 135]. In these experiments, a series of odd harmonics was applied from which every third or fourth frequency was removed. They were 1, 3, 9, 11, 15, 17, 21... or 3, 5, 7,11, 15, 17, 19, 21, 25... This method was applied to study organic coatings on A1 [125], The signal contained frequencies between 0.1 Hz and 

FT-based measurements allow for faster measurements because all the frequencies are applied at the same time, and to carry out impedance measurements during the potential sweep, it is assumed that the changes during the data block used for transformation are negligible (pseudostationary). FT-based measurements also permit one to determine time variance and nonlinear distortions in the data. However, the cost of this convenience is a lower amplitude for each frequency compared to classical EIS. This produces a weaker signal and larger noise. The interest in this method is constantly increasing. 

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Darowicki K, Kawula J (2004) Validity of impedance spectra obtained by dynamic electrochemical impedance spectroscopy verified by Kramers-Kronig transformation. Pol J Chem 78(9) 1255-60... 

Dahlstrom PK, Harrington DA, Seland F (2012) A study of methanol oxidation by dynamic electrochemical impedance spectroscopy. ECS Trans 41 35-47... 

Fig. 3.12 Schema of dynamic electrochemical impedance spectroscopy system (From Ref. [133]. Reproduced by permission of Electrochemical Society)...

K. Darowicki, P. Slepski, Dynamic electrochemical impedance spectroscopy of the first order electrode reaction, J. Electroanal. Chem., 2003,547, pp. 1-8. 

Although not dealt with in this chapter, AC impedance measurements (sometimes called electrochemical impedance spectroscopy) are important in studying electrode dynamics. Generally in this method, a sinusoidal voltage (10 2 to 105 Hz) is applied to the cell, the phase angle and the amplitude of the response current are measured as a function of... 

The coupling of biomimetic dynamic interfaces with electrochemical impedance spectroscopy has shown value in the study of ion transport studies across tethered bilayers [56]. Electrochemical impedance spectroscopy may prove valuable used in conjunction with the previously described techniques [57, 58]. Again electrode construction with readily chemically adaptable surface materials such as gold, silver and glass/silica amongst others make this a promising approach for introducing functional interfaces. 

Conventional kinetics is largely concerned with the description of dynamic processes in the time domain, and in consequence few conceptual problems are encountered in understanding time resolved experiments. By contrast, frequency resolved measurements often pose more of a challenge to understanding, in spite of the obvious correspondence between the time and frequency domains. This conceptual difficulty may explain why the only frequency resolved method to achieve universal acceptance in electrochemistry is electrochemical impedance spectroscopy (EIS) [27-29], which analyses the response of electrochemical systems to periodic (sinusoidal) perturbations of voltage or current. It is clear that EIS is a very powerful method, and there... 

Besides these potentiometric-based methods, a series of electrochemical techniques can be applied to the detection of biomolecular interactions. Depending on the desired dynamic detection range and the specific properties of the system under study, techniques such as electrochemical impedance spectroscopy, voltage step capacitance measurements, amperometry, differential pulse voltammetry, square wave voltammetry, AC voltammetry, and chronopotentiomet-ric stripping analysis can be used for label-free detection of DNA, proteins, and peptides [1]. Often these techniques require the use of redox mediators. Electrochemical impedance spectroscopy (EIS), in particular, is a very promising technique for DNA biosensing [2,3]. 

In this work, it will be demonstrated that simultaneous acquisition and analysis of impedance and gravimetric data in a single cyclic potential scan (Fig. 1) enables a detailed electrochemical characterization of dynamic non-stationary eleetrode/eleetrolyte interfaces. The combination of electrochemical impedance spectroscopy (EIS) and electrochemical quartz crystal microbalance (EQCM) techniques is used to characterize the underpotential... 

Figure 16.1 Relaxation times of physical processes present in fuel cell operation and corresponding electrical measurement techniques. The dynamic range spans over 15 orders of magnitude. Fast processes are covered by electrochemical impedance spectroscopy.

As discussed in piAL 11], using electrochemical impedance spectroscopy (EIS) to analyze a PEM electrolyzer very clearly reveals slow diffusion dynamics (very low frequencies), and less clearly, fast diffusion dynamics (low/medium frequencies) and very fast diffusion dynamics (high/very high frequencies). As, for our purposes, the truth of this observation is veiy comprehensive, we shall consider it to be general hereafter. 

Analyzing the dynamic behavior of a corrosion system requires special techniques, which differ essentially from conventional dc techniques, such as measurements of the open circuit potential, polarization curves, weight loss, or other physicochemical parameters. Based on dynamic system analysis and linear system theory (LST), electrochemical impedance spectroscopy (EIS) is one of the most powerful nonconventional techniques. 

The two preceding electroanalytical techniques, one in which the measured value was the current during imposition of a potential scan and the other a potential response under an imposed constant current, owe their electrical response to the change in impedance at the electrode-electrolyte interface. A more direct technique for studying electrode processes is to measure the change in the electrical impedance of an electrode by electrochemical impedance spectroscopy (EIS). To relate the impedance of the electrode-electrolyte interface to electrochemical parameters, it is necessary to establish an equivalent circuit to represent the dynamic characteristics of the interface. 

Dynamic behavior of an ensemble or array of nanomaterial is dependent on the time scale in chronoamperometry, frequency in electrochemical impedance spectroscopy (EIS) and scan rate for a voltammetric measurement. It depends on three parameters diffusion or depletion layer thickness ( ), size or radius of curvature of each nanocomponent ((), spaeing between nanocomponents in sparse distribution or width of nanodeposit or roughness For sparse nanostructures, response switch between kinetic or... 

Yun et al. developed a label-free immunosensor based on aligned MWCNT arrays. Antibodies were attached to MWCNT ends, and binding of model antigen mouse IgG to the antibody-modified surface resulted in an increase in the electron-transfer resistance. Formation of the antibody-antigen complex was monitored by CV and electrochemical impedance spectroscopy (EIS), resulting in a DL of 200 ng mL with a dynamic range up to 100 pg mL for IgG. 

In this regard perturbation analysis like step analysis and electrochemical impedance spectroscopy (EIS) can show the way (Choudhury et al., 2005, Jenseit et al., 1993). The popular trend of using transmission line model for EIS analysis may not be sufficient to diagnose the dynamic mechanisms. Thus to understand and decouple the effects, there is a need to develop and validate comprehensive transient models based on first principles. With the availability of increased computational power it may be possible to develop online fault diagnosis analyzer systems for the actual field units. 

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