Electrochemical impedance spectroscopy transfer function

The methods described in this chapter and this book apply to electrochemical impedance spectroscopy. Impedance spectroscopy should be viewed as being a specialized case of a transfer-function analysis. The principles apply to a wide variety of frequency-domain measurements, including non-electrochemical measurements. The application to generalized transfer-function methods is described briefly with an introduction to other sections of the text where these methods are described in greater detail. Local impedance spectroscopy, a relatively new and powerful electrochemical approach, is described in detail. 

While the emphasis of this book is on electrochemical impedance spectroscopy, the methods described in Section 7.3 for converting time-domain signals to frequency-domain transfer functions clearly are general and can be applied to any t3q>e of input and output. Some generalized transfer-function approaches are described in Chapters 14 and 15. 

C. Gabrielli and B. Tribollet, "A Transfer Function Approach for a Generalized Electrochemical Impedance Spectroscopy," Journal of The Electrochemical Society, 141 (1994) 1147-1157. 

The interfacial reactivity of functional electrodes can mostly influence the amperometric detection signal in the bioelectrocatalytic process. Herein, the electrochemical impedance spectroscopy (EIS) has been applied to investigate the interfacial charge transfer or mass transfer process of bare Ti02/Ti substrates and G0D-Ti02/Ti composite electrodes. The EIS measurements over a frequency from 100000 to 0.01 Hz are carried out in a conventional three-electrode system under a sinusoidal perturbation of 5 mV and a constant potential of -0.4 V. 

IMPS uses modulation of the light intensity to produce an ac photocurrent that is analysed to obtain kinetic information. An alternative approach is to modulate the electrode potential while keeping the illumination intensity constant. This method has been referred to as photoelectrochemical impedance spectroscopy (PEIS), and it has been widely used to study photoelectrochemical reactions at semiconductors [30-35]. In most cases, the impedance response has been fitted using equivalent circuits since this is the usual approach used in electrochemical impedance spectroscopy. The relationship between PEIS and IMPS has been discussed by a number of authors [35, 60, 64]. Vanmaekelbergh et al. [64] have calculated both the IMPS transfer function and the photoelectrochemical impedance from first principles and shown that these methods give the same information about the mechanism and kinetics of recombination. Recombination at CdS and ZnO electrodes has been studied by both methods [62, 77]. Ponomarev and Peter [35] have shown how the equivalent circuit components used to fit impedance data are related to the physical properties of the electrode (e.g. the space charge capacitance) and to the rate constants for photoelectrochemical processes. 

This operation determines the values of R and C that, in series, behave as the cell does at the measurement frequency. The impedance is measured as a function of the frequency of the ac source. The technique where the cell or electrode impedance is plotted V5. frequency is called electrochemical impedance spectroscopy (EIS). In modem practice, the impedance is usually measured with lock-in amplifiers or frequency-response analyzers, which are faster and more convenient than impedance bridges. Such approaches are introduced in Section 10.8. The job of theory is to interpret the equivalent resistance and capacitance values in terms of interfacial phenomena. The mean potential of the working electrode (the dc potential ) is simply the equilibrium potential determined by the ratio of oxidized and reduced forms of the couple. Measurements can be made at other potentials by preparing additional solutions with different concentration ratios. The faradaic impedance method, including EIS, is capable of high precision and is frequently used for the evaluation of heterogeneous charge-transfer parameters and for studies of double-layer structure. 

In fact, ac electrogravimetry is the combination of electrochemical impedance spectroscopy with a fast quartz crystal microbalance. The fluxes of all mobile species are considered, and the usual conditions and treatments of EIS are applied. Beside the electrochemical impedance, an electrogravimetric transfer function, Aw/A ((o), can be derived which contains the dependences of the fluxes of anions, cations and solvent molecules, respectively, on the small potential perturbation. The complex plane plot representations of electrogravimetric transfer functions for PANI are shown in Figs. 3.17 and 3.18. 

Electrochemical impedance spectroscopy (EIS including Faradaic impedance in the presence of a redox probe and non-Faradaic-capacitance methods) is considered as a rapid technique for the characterization of the structure and functional operation of biomaterial-functionalized electrodes (Yang and Bashir, 2008). The immobilization of biomaterials on electrodes produces changes in the capacitance and interfacial electron transfer resistance of electrodes, causing changes in the impedance. Flence, interfacial... 

A parallel development has taken place for related transfer-fimction methods. For electrochemical systems, impedance spectroscopy, which relies on measurement of current and potential, provides the general system response. As described in Chapters 14 and 15, transfer-function methods allow the experimentalist to isolate the portion of the response associated with specific inputs or outputs. 

Song, H. and Macdonald, D.D. (1991) Photoelectrochemical impedance spectroscopy I. Validation of the transfer function by Kramers-Kronig transformation. Journal of The Electrochemical... 

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