Electronic impedance spectroscopy

Electronic impedance spectroscopy (EIS) is used to measure the polymer dielectric properties and the changes in these properties with exposure time. This is based on the interaction of an external field with the electric dipole moment of the sample, often expressed by permittivity. Dielectric thermal analysis (DETA) measures the permittivity, capacitance and dielectric loss of a polymer sample under an oscillating electric field as a function of temperature. The dielectric properties of a blend system in general depend on structure, crystallinity, morphology and additives. " ... 

In situ electron transport measurements on conducting polymers are commonly made by using a pair of parallel-band electrodes bridged by the polymer [Fig. 9(A)].141142 Other dual-electrode techniques in which the polymer film is sandwiched between two electrodes [Fig. 9(B)],139,140 rotating-disk voltammetry [Fig. 9(C)],60,143 impedance spectroscopy,144,145 chronoamperometry,146 and chronopotentiometry147 have also been used. 

Impedance spectroscopy is best suited for the measurement of electronic conductivities in the range 10 -7to 10 2S cm 1.145 In principle, it is perhaps the best method for this range, but it is often difficult to interpret impedance data for conducting polymer films. The charge-transfer resistance can make measurements of bulk film resistances inaccurate,145 and it is often difficult to distinguish between the film s ionic and electronic resistances.144 This is even more of a problem with chronoamperometry146 and chronopotentiometry,147 so that these methods are best avoided. 

Impedance, for measurement of the potential of zero charge, 35 Impedance blocks, for polypyrrole, 577 Impedance spectroscopy of electronically conducting polymers, 576 Indium... 

AC Impedance spectroscopy, 237 Auger electron spectroscopy, AES, 254 High resolution electron energy loss spectroscopy, HREELS, 43, 69 Infrared spectroscopy, IRS, 39, 69 Surface enhanced Raman spectroscopy, SERS, 256... 

Impedance Spectroscopy, 21-22 Inner sphere electron transfer, 47-48 Ion transfer reaction, 39-40... 

The initial stages, notably the formation of a monolayer on a foreign substrate at underpotentials, were mainly studied by classical electrochemical techniques, such as cyclic voltammetry [8, 9], potential-step experiments or impedance spectroscopy [10], and by optical spectroscopies, e.g., by differential reflectance [11-13] or electroreflectance [14] spectroscopy, in an attempt to evaluate the optical and electronic properties of thin metal overlayers as function of their thickness. Competently written reviews on the classic approach to metal deposition, which laid the basis of our present understanding and which still is indispensable for a thorough investigation of plating processes, are found in the literature [15-17]. 

Within the electroanalytical sector, potentiometry and voltammetry are the principal methods applied in electronic tongue studies, followed by impedance spectroscopy. 

The state of charging, mainly of sealed cells, can be studied using galvanos-tatic methods [353] and electrochemical impedance spectroscopy [354-356] (see reviews [357, 358]). The battery behavior was analyzed using electronic network modeling [359, 360]. 

It should also be recalled that a full electrochemical, as well as spectroscopic and photophysical, characterization of complex systems such as rotaxanes and catenanes requires the comparison with the behavior of the separated molecular components (ring and thread for rotaxanes and constituting rings in the case of catenanes), or suitable model compounds. As it will appear clearly from the examples reported in the following, this comparison is of fundamental importance to evidence how and to which extent the molecular and supramolecular architecture influences the electronic properties of the component units. An appropriate experimental and theoretical approach comprises the use of several techniques that, as far as electrochemistry is concerned, include cyclic voltammetry, steady-state voltammetry, chronoampero-metry, coulometry, impedance spectroscopy, and spectra- and photoelectrochemistry. 

Impedance Spectroscopy for More Complex Interfacial Situations. The electrochemical interfacial equivalent circuits shown in Figs. 7.48 and 7.49 are the simplest circuits that can be matched to actual electrochemical impedance measurements. The circuit in Fig. 7.49 would be expected to apply to an electrode reaction that involves only electron transfer (e.g., redox systems of the type Fc3+ + e Fe2+), no adsorbed intermediate. 

Figure 48. The concentration cell experiment together with impedance spectroscopy allows one to separate ionic (

These examples and the general subjects mentioned above illustrate that ion conduction and the electrochemical properties of solids are particularly relevant in solid state ionics. Hence, the scope of this area considerably overlaps with the field of solid state electrochemistry, and the themes treated, for example, in textbooks on solid state electrochemistry [27-31] and books or journals on solid state ionics [1, 32] are very similar indeed. Regrettably, for many years solid state electrochemistry/solid state ionics on the one hand, and liquid electrochemistry on the other, developed separately. Although developments in the area of polymer electrolytes or the use of experimental techniques such as impedance spectroscopy have provided links between the two fields, researchers in both solid and liquid electrochemistry are frequently not acquainted with the research activities of the sister discipline. Similarities and differences between (inorganic) solid state electrochemistry and liquid electrochemistry are therefore emphasized in this review. In Sec. 2, for example, several aspects (non-stoichiometry, mixed ionic and electronic conduction, internal interfaces) are discussed that lead to an extraordinary complexity of electrolytes in solid state electrochemistry. 

Owing to its extraordinary chemical stability, diamond is a prospective electrode material for use in theoretical and applied electrochemistry. In this work studies performed during the last decade on boron-doped diamond electrochemistry are reviewed. Depending on the doping level, diamond exhibits properties either of a superwide-gap semiconductor or a semimetal. In the first case, electrochemical, photoelectrochemical and impedance-spectroscopy studies make the determination of properties of the semiconductor diamond possible. Among them are the resistivity, the acceptor concentration, the minority carrier diffusion length, the flat-band potential, electron phototransition energies, etc. In the second case, the metal-like diamond appears to be a corrosion-stable electrode that is efficient in the electrosyntheses (e.g., in the electroreduction of hard to reduce compounds) and electroanalysis. Kinetic characteristics of many outer-sphere... 

The second meaning of the word circuit is related to electrochemical impedance spectroscopy. A key point in this spectroscopy is the fact that any -> electrochemical cell can be represented by an equivalent electrical circuit that consists of electronic (resistances, capacitances, and inductances) and mathematical components. The equivalent circuit is a model that more or less correctly reflects the reality of the cell examined. At minimum, the equivalent circuit should contain a capacitor of - capacity Ca representing the -> double layer, the - impedance of the faradaic process Zf, and the uncompensated - resistance Ru (see -> IRU potential drop). The electronic components in the equivalent circuit can be arranged in series (series circuit) and parallel (parallel circuit). An equivalent circuit representing an electrochemical - half-cell or an -> electrode and an uncomplicated electrode process (-> Randles circuit) is shown below. Ic and If in the figure are the -> capacitive current and the -+ faradaic current, respectively. 

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