Normalized Tafel plots

This equation can be useful for obtaining kinetic parameters for systems in which the normal Tafel plots are complicated by mass-transfer effects. 

Fig. 2 The measured and normalized Tafel plots of thermally and sol-gel prepared DSA for the chlorine evolution reaction. The normalized data correspond to the electronic electrocatalytic factor...

Figure 5.2 RDE voltammogram (VA) and normalized Tafel plot (NTP) obtained for the system Cu Cu(ll), glycine.

Surface concentrations of complex species and ligands can be determined by means described in Chapter 3 further, the normalized Tafel plots (NTPs) can be obtained. However, initially, we shall make use of isosurface concentration voltammetry presented in Section 5.3.1. Using experimental data obtained at constant surface concentrations, one can estimate the value of without any tentative assumptions as to the mechanism of the charge transfer step, that is, for unknown composition of the EAC. It follows from Eq. (4.3) that for t/r = const, the surface concentrations of the components do not depend on time. Selected in this way, data (Figure 8.7) are satisfactorily approximated by the lines with similar slopes, which yield = 0.37 0.03 (see Eq. (8.17)). This value canbe checked by the analysis of individual transients of the potential, but then the composition of the EAC must be established. 

Figure 8.8 Normalized Tafel plots obtained from chronopotentiometric data at cathodic current densities, as indicated. Determined from this NTP kinetic parameters are aiso listed.

Figure 8.16 Normalized Tafel plots obtained by transformation of IPS (malic and tartaric acid systems) and RDE (gluconic acid system) voltammograms. 0.3-0.5M sulfate was used as a supporting electrolyte.

Normalized Tafel plots obtained by transformation of RDE voltammograms. 

Figure 8.25 Normalized Tafel plots obtained from RDE voltammograms at different pH. CuL - species is treated as the EAC.

Figure 9.30 Normalized Tafel plots obtained for 0.01 M Cu(ll) containing different amounts of tetraethylene glycol and 30 pM of chloride (upper part, ordinate to the left) or bromide (lower part, ordinate to the right).

Notice that the same data can be presented as E functions, because the interrelation between surface Cj [ and E is easily obtained. This makes it possible to assign the value of [H+] at any potential of voltammograms and to transform them into normalized Tafel plots (NTPs). Some results of the procedures performed are shown in Figure 11.6. The data obtained at different v are very close and can be approximated by one average NTP. The kinetic parameters of charge transfer... 

Figure 11.6 Normalized Tafel plots obtained at different potential sweep rates for 0.04M glycolic (upper part) and tartaric (lower part) acid solutions. Indicated kinetic parameters are calculated from general regression lines.

Fig. 9.21. Tafel plots of the (a) anodic and (b) cathodic current densities for film thickness varying from 4 to 40 A in steps of 6 A. The cathodic curves have been normalized forr = 0. Barrier height= 1.5 eV. VL=VR= 1.5 harmonic. (Reprinted with permission from W. Schmickler and J. Ulstrup, J. Chem. Phys. 19 217, Fig. 3, copyright 1989, American Chemical Society.)...

Figure 6 shows logarithmic plots of modulus j vs. 17 with data calculated from eqn. (80). Normalized linear Tafel plots are apparent from overpotentials of about 0.1 V. As is apparent from Fig. 6, at this value of overpotential the exponential due to the opposite reaction can be dropped in eqn. (80). 

Fig. 16.4. A Tafel plot for the situation represented in Fig. 16.3 (in normal representation rotated 90° anticlockwise).

Figure 25 Tafel plots for chlorine evolution in 1 M NaCl/3M NaC104/0.01 M HCIO4. Current values are normalized to the number of surface sites. Electrode (geometric) area = 0.785 cm. (Reprinted with permission from A. De Battisti, S. Ferro, M. Dal Colle, /. Phys. Chem. B, 105, 1679. Copyright 2001, The American Chemical Society.)...

As far as the chl.e.r. mechanism is concerned, the same, previously described, investigation has been performed and Figures 24 and 25 respectively report the polarization curve and the Tafel plot (currents normalized to the number of active sites at the electrode surface), for the case of a 1 M NaCl/3 M NaC104/0.01 M HCIO4 test solution. The measured Tafel slope has a value of 0.149 V, and the reaction order with respect to CP is about 0.7 the values of b and R both agree well with a Volmer-Heyrovsky mechanism [24], with a rate-determining electrochemical desorption, provided a value of about 0.7 is assumed for the coverage by the intermediate chlorine radicals [28] ... 

Fig. 17.2 Tafel plots for the (normalized, dimensionless) current, yjy, that accompanies hydrogen evolution in a solution containing 3.4 mM HCl + 1.0 M KCl, corrected for diffuse-double-layer effects, mass transport controlled kinetics and ohmic potential drop, measured at three temperatures (5, 45, 75°C all results fall on the same line of this reduced plot) at a dropping mercury electrode. The slope obtained from this plot is 0.52, independent of temperature. (Based on data from E. Kirowa-Eisner, M. Schwarz, M. Rosenblum, and E. Gileadi, J. Electroanal. Chem. 381, 29 (1995) and reproduced by the authors.)...

Fig. 13 Upper part Tafel curves for ETR on passive iron [24]. The /-values of different authors were normalized taking the ratio ijc. Lower part transfer coefficients taken from the Tafel plot in dependence on the band bending U — Ufb-...

Fig. 5 Theoretical Tafel plots as a function of the reorganization energy. The plots are normalized with respect to the standard rate constant at/) = 0V and A = 1.0 eV. The relative values of are 175 for A = 0.5 eV and 0.0064 for A = 1.5 eV.

Tafel Plots Normalized with Respect to the Surface Concentration of EAC... 

Figure 8.30 Comparison between experimental RDE voltammograms (symbols) and theoretical curves simulated with the indicated kinetic parameters. Tafel plots normalized to the ratio f = [SnLH"]j/[SnLH"](, are shown in the inset.

Figure 9.5 Tafel plots normalized to the ratio of Cj/Cg, where c is the respective concentration of the electrically active complex given at the plots. Transformation of RDE voltammet-...

While the constants and in the Tafel equation (Equation 11.10) can be estimated from the reaction kinetic parameters, these are normally given directly by the linear fit of the Tafel plot for current-polarization or q-ln j measurement for the electrochemical reaction at higher over potential values. Also, with the known values of the/-axis intercept and the Tafel slope of the linear part of the Tafel plot from the linear fit equation, the exchange current density, jo, and transfer coefficient, a, can be computed. 

Figure 4.23 Experimental Tafel plot of cell voltage versus current, corrected for fuel cell ohmic and other losses, so that only cathode polarization losses are remaining. The results are normalized to platinum loading. Results with open circles are with humidified oxygen, and closed circles are with humidified air. The dashed line represents the Tafel slope behavior. Note that for all loadings the Tafel slope for oxygen reduction on platinum is the same but deviates from this behavior under mass-limiting behavior. Also note that the vertical axis is ohmic corrected fuel cell voltage, not electrode overpotential, so the voltage falls with increasing current density. (Reproduced with permission from [9].)...

Tafel plot for redox currents on passivated Fe with different redox systems, i/c = current density normalized for the concentration of the redox system c. (From Schmiclder, W. and Schultze, J.W., in Modem Aspects of Electrochemistry, Vol. 17, J.fXM. Bockris, B.E. Conway, R.E. White, eds.. Plenum Press, New York, p. 357,1986.)... 

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