Cyclic voltammograms dependence

Therefore, given that a multi-electron process can be described as a series of one-electron transfers, more or less separated from each other, the shape of the cyclic voltammogram depends on the following factors 14... 

In heterogeneous electron transfer experiments, the gold electrode with a monolayer film is placed in contact with the solution containing a redox couple [such as Fe(CN)63-/Fe(CN)64- etc.]60-63. The shape of the cyclic voltammogram depends on how effectively the monolayer blocks access for the redox probe to the electrode surface. This method is therefore invaluable for permeability studies. Absence of redox waves close to the formal potential of the probe indicates that the monolayer is completely impermeable for redox probe species. On the other hand, the presence of a redox wave shows either that the monolayer is loosely packed and easily penetrated by external molecules, or the presence of numerous defects and pin-holes in the monolayer. 

Figure 4. (A) Cyclic voltammograms over a range of scan rates for a redox polymer (poly-[Fe 5-amino-1,10-phenanthrotme)3]3+/>)91 and (B) p-doping and undoping of a conducting polymer (polypyrrole) (B). [(A) Reprinted from X. Ren and P. O. Pickup, Strong dependence of the election hopping rate in poly-tris(5-amino-1,10-phenan-throline)iron(HI/II) on the nature of the counter-anion J. Electroanal. Chem. 365, 289-292,1994, with kind permission from Elsevier Sciences S.A.]...

The unusual cyclic voltammograms and responses to large-amplitude potential steps of a variety of conducting polymer films have prompted a number of groups to develop nucleation models for their oxidation. The key features that they have sought to explain are the peaks observed in anodic chronoamperometry (see Fig. 14), and the dependence of the anodic peak position on scan rate207 and the time spent in the undoped state.20 ... 

In practice, AGq will also depend on the coverage of the adsorbate, 6. Since this effect has direct implications for cyclic voltammetry, it will be discussed in more detail in Section 3.3.1 on theoretical cyclic voltammograms. 

FIG. 13 Cyclic voltammogram (a) and potential dependence of the photoresponses (b)-(c) to chopped illumination and lock-in detection associated with the photoreaction in Eq. (40). The CV shows that the polarizable window extended to less than 100 mV. The photocurrent measurements carried out were done in the presence (trace 3) and absence (trace 2) of the redox quencher in the organic phase. (Reprinted with permission from Ref 48. Copyright 1989 American Chemical Society.)... 

FIG. 7 The quinacrine-dependent changes in cyclic voltammograms of the DNA-immobilized An electrode. Experimental conditions are the same as those in Fig. 5. 

Cyclic voltammograms of solutions of the pyrrole monomers also show a dependence on the anion present in the electrolyte and can show multiple peaks with Epa values ranging from + 1.0 to + 1.3 V in acetonitrile [57,279]) (+ 0.8 to + 1.1 V vs. 

The cyclic voltammograms of these systems display quasi-reversible behavior, with AEv/v being increased because of slow electrochemical kinetics. Standard electrochemical rate constants, ( s,h)obs> were obtained from the cyclic voltammograms by matching them with digital simulations. This approach enabled the effects of IR drop (the spatial dependence of potential due to current flow through a resistive solution) to be included in the digital simulation by use of measured solution resistances. These experiments were performed with a non-isothermal cell, in which the reference electrode is maintained at a constant temperature... 

Figure 12. Dependence of the anodic peak current /peak on the potential scan rate v on a logarithmic scale obtained from the cyclic voltammograms for (a) Pt/polished AI2O3, (b) Pt/etched Ni, and (c) Pt/unpolished AI2O3 electrodes. The slope a means (d log /peak / d log v). Here, 14 and v0 means the upper and lower threshold scan rate, respectively. Reprinted from J. -Y. Go et al., A study on ionic diffusion towards self-affine fractal electrode by cyclic voltammetry and atomic force microscopy, J. Electroanal. Chem. 549, p. 49, Copyright 2003, with permission from Elsevier Science.

When the B/C conversion is fast, C is produced close to the electrode surface and is likely to diffuse back and be oxidized there. The situation is similar to the ECE case in the ECE-DISP problem discussed in Section 2.2.5. In the ECE case, the cyclic voltammetric responses depend essentially on the dimensionless rate constant, 2 = (7ZT/F)(k/v), of the B/C reaction in the framework of two subcases according to the order in which the two standard potentials, Z yBand c, lie (note that in the D/C couple, D is the oxidized form). Typical cyclic voltammograms are shown in Figure 2.25a and b for the two subcases. 

Thus, the dimensionless current-potential curves depend on the dimensionless parameters 1, A, A , oq, and a2. Simulating the dimensionless cyclic voltammograms then consists of finite difference resolutions of equations (6.57) and (6.58), taking into account all initial and boundary conditions. Examples of such responses are given in Section 2.5.2 (Figure 2.35). 

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