Nyquist impedance

Introducing the complex notation enables the impedance relationships to be presented as Argand diagrams in both Cartesian and polar co-ordinates (r,rp). The fomier leads to the Nyquist impedance spectrum, where the real impedance is plotted against the imaginary and the latter to the Bode spectrum, where both the modulus of impedance, r, and the phase angle are plotted as a fiinction of the frequency. In AC impedance tire cell is essentially replaced by a suitable model system in which the properties of the interface and the electrolyte are represented by appropriate electrical analogues and the impedance of the cell is then measured over a wide... 

It is now time to look at the Nyquist impedance plot of a real cell. Figure 8.12(a) shows such an impedance plot for the all-solid-state cell, IT0/W03/PE0-H3P04/1T0(H), at 8°C. The two ITO layers are needed as transparent electronic conductors (cf. Section 8.1.2). 

The Nyquist impedance plots for the cells with Nafion 117 and Nafion 112 at room temperature with fully humidified reactant gases were shown in Figure 5.32... 

FIGURE 8.1 Nyquist impedance plot for a zeolite Y-associated poly(p-phenylenevinylene)... 

Figure 5.33 presents the effect of particle size on the Nyquist impedance behavior of the electrode [75]. The plot shows that the effect of particle size is opposite to that of the diffusion coefficient, that is, a decrease in the particle radius shifts the appearance of the transition region to higher frequencies. In smaller particles, hydrogen needs to travel only... 

Fig. 5. 33 Change in the Nyquist impedance due to variation in the average particle size of the metal hydride electrode. The simulations were done at a diffusion coefficient value of 2.0 x 10 ° cmVs [75].

When a charge transfer proceeds at the electrode, the equivalent circuit consists of Cd and the charge-transfer resistance Ra. in parallel. Therefore, the corresponding Nyquist impedance plot represents a semicircular arc. Analogous to the case just considered above, a replacement of Cd by the CPE leads to a change from a semicircular arc to a depressed semicircular arc. 

Fig. II.5.5 Nyquist impedance plot due to finite length diffusion with a transmissive boundary condition...

Fig. IL5.7 Nyquist impedance plot due to a porous electrode with log-normal distribution of the pore sizes and with double-layer charging only...

The EIS method can also be employed to reveal the properties of different electrolytes with the same electrode active material. Bettini et al. [55] reported the Nyquist impedance profiles of four different ILs (l-dodecyl-3-methylimidazolium... 

Impedimetric Biosensors for Nano- and Microfluidics, Fig. 10 The principle of IME impedimetric detection of the antibody immobilization and the bacterial attachment, (a) Nyquist impedance spectra of the IME-based biosensor upon antibody immobilization and bacterial attachment with different number of E. coli 0157 H7 cells on their surface, a = antibodies only, b = 4.36 x 10 OTJ/ml, c = 4.36 x 10 CFUAnl, d = 4.36 x 10 CHJ/ml, and e = 4.36 x 10 CEU/ml. Data points from left to right correspond to decreasing frequency. Amplitude voltage 5 mV Electrolyte 10 mM [EefCNlg] (1 1) in 0.01 M PBS, pH 7.4. (b) The linear relationship betwetm the electron transfer resistance and logarithmic value of E. coli concentrations daived from Fig. 10a... 

Figure 4.4.33. Nyquist impedance diagrams for Alloy-22 in deaerated, saturated NaCl (6.2 m) -I-0.001 m HCl (pH = 3) solution at 80°C as a function of potential in the passive state, showing a comparison between the experimental and simulated data, with the latter being calculated from parameter values obtained by optimization of the reduced PDM (Figure 4.4.32) on the experimental data (After D. Macdonald et al. [2004]).

For detailed investigations of electrodes, more complex equivalent circuits are necessary which are described in the literature [7,8]. In solid-state electrochemistry mostly Nyquist impedance plots are used, which are suited to ... 

Figure 2.21. Nyquist impedance in the Randles model (model with C in black model with CPE in gray)...

Nyquist impedance plot comparing ideal vertical impedance of capacitor (thin line) and that of supercapacitor (thick line). Equivalent series resistance (ESR) is derived from the intercept of the real impedance axis followed by the equivalent distributed resistance (EDR) of a porous electrode. Source Kotz, R. 2000. Electrochimica Acta, 45,2483-2498. With permission.)... 

TSC inhibitor [26], Notice from this Figure 3.11 that the Nyquist impedance semicircles increase with increasing content of the TSC inhibitor. This implies that the polarization resistance (iip) also increases with additions of this inhibitor, which in turn, decreases the corrosion rate (Cji) as indicated in Table 3.3. 

Fig. 9.13 (a) Nyquist Impedance (Z) plots for MEAs made with the Nafion 1,135 and the Nafion/ S-SWCNT eomposite membrane. The measurements carried out at room temperature with a flow of humidified and O. Insert the high-frequency range at higher magnification, (b) polarization curve for the Nafion 1,135 and theNafion/S-SWCNT composite membrane obtained at 60°C with... 

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