Anodic voltammograms

Equations (58) and (66) give us the expression required to simulate the voltammograms and what they change as a function of the different chemical or electrochemical variables. 

---

The characteristic shape of the anodic voltammogram of a Si electrode in aqueous fluoride media, as shown for example in Fig. 3. Id, is surprisingly stable against changes in fluoride concentration (cF) or pH. When the potential of a p-type Si electrode is swept anodic of OCP a steep current rise near 0 V is observed, followed by a sharp peak (Jj) and a narrow plateau (J2). Then a second broad maximum (Ji) is found around a positive bias of 1.5-2.5 V, followed by a broad plateau (J4) extending over several volts, as shown in Fig. 4.7. When electrode rotation is used, these curves are pen-reproducible for a given solution. The hysteresis of the curves approaches zero for slow sweeps [Ch3]. 

Figure 4. Anodic voltammograms on various Ft single-crystal electrodes in 0.5Af H2SO4. The sweep rate was 50 mV s f (From Ref. 30.)...

Figure 5. (A) Voltammograms on Ir and Pt low-index single crystals at 50 mV s in O.SM H2SO4. Solid curves are for Ir and dotted ones for Pt. (B) Anodic voltammograms on various iridium single crystals. (From Ref. 32.)...

Figure 3.13 Electrochemical oxidation of HOOH and reduction of its products at GC electrodes in MeCN (0.1 M TEAP) (a) linear-sweep anodic voltammograms for (A) 0, (B) 0.3, (C) 1.7, and (D) 3.3 mM HOOH (scan rate 2 V min-1 electrode area, 0.46 cm2) (b) rotated-ring electrode cathodic voltammogram (scan rate 10 mV s-1) of the product from the oxidation of 4 mM HOOH at the rotated-disk electrode (rotation rate 1600 rpm) for (A) ED disconnected, and (B) En = +2.6 V versus SCE (c) rotated-ring electrode cathodic voltammogram (scan rate 10 mV s-1) of the products from the oxidation of 1 mM HOOH at the rotated-disk electrode (rotation rate 4900 rpm) for (A) disconnected and (B) ED = +2.6 V versus SCE.

With particular attention to excess interface electrons, an anodic procedure has been performed for n-type InP (100). The anodic voltammogram was similar to Figure 15. No specific characteristics have been observed and a stable overlayer of indium sulfide has been formed. Equations 4, 5 and 6 show the reaction mechanism of aqueous (NH S solution with the InP substrate during anodic sulfidation. Equation 5 is responsible for the anodic dissolution of InP in (NH S solution when the hydroxyl group is dominating the solution. Equation 6 is the one responsible for sulfidation and depositing sulfides. 

Figure 1. Change in the shape of FLINAK-Na20 anodic voltammograms on exposition at 700°C. (initial O concentration 3.9910 Wo) V=0.1V s A=0.21cm exposition time, hours 1- 0,...

Figure 4.7 Anodic voltammograms simulated for model system at different ratios r = Ci/Cf. Anodic i is normalized with respect to the cathodic iimiting current density i. ...

Figure 1. Cyclic voltammograms obtained at v=0,002 V/s on Pt(Pt)-electrode in 0,1M NaOH (1) with additives of 0,03 M of a-alanine (2) and 0,03M of glycine (3) (a) - section of the anodic voltammogram obtained at v = 0,01 V/s during oxidation of Gly (0,05M) from the adsorbed state on...

Potential-excitation signal and voltammogram for anodic stripping voltammetry at a hanging mercury drop electrode. 

The Kad Fischer jack on the back of most pH meters, used to monitor Kad Fischer titrations, suppHes a constant regulated current to the cell, which can consist of two identical (platinum) working electrodes. The voltammograms shown in Figure 9 illustrate the essential features of this technique. The initial potential difference, AH, is small because both redox forms of the sample coexist to depolarize the electrodes. The sample corresponds to the wave on the right-hand (cathodic) side of each figure and is therefore easily oxidized. The titrant is represented by the wave on the left-hand (anodic) side and is therefore easily reduced. Halfway to the end point the potential difference,, remains small, but at the end point the potential difference,... 

Fig. 9. Voltammograms demonstrating a potentiometric titration using dual-polarized electrodes, where the dashed lines indicate the anodic and equal-but-opposite cathodic currents that must be carded by the two opposing electrodes during the titration. Terms are defined in text.

Flavin adenine dinucleotide (FAD) has been electropolymerized using cyclic voltammetry. Cyclic voltammograms of poly (FAD) modified electrode were demonstrated dramatic anodic current increasing when the electrolyte solution contained NADH compare with the absence of pyridine nucleotide. 

Figure 6.2-11 Cyclic voltammogram of dry [BMIM] PFg on Au(in) between the anodic and...

Voltaic cells 64. 504 Voltammetry 7, 591 anodic stripping, 621 concentration step, 621 mercury drop electrode, 623 mercury film electrode, 623 peak breadth, 622 peak current, 622 peak potential, 622 purity of reagents, 624 voltammogram, 622 D. of lead in tap water, 625 Volume distribution coefficient 196 Volume of 1 g of water at various temperatures, (T) 87... 

FIGURE 3-12 Anodic shipping voltammetry the potential-time waveform (a), along with the resulting voltammogram (b). 

Equations (57) and (58) describe the electrochemical oxidation of conducting polymers during the anodic potential sweep voltammograms (/f vs. q) or coulovoltagrams (Qr vs. tj) under conformational relaxation control of the polymeric entanglement initiated by nucleation in the reduced film. They include electrochemical variables and structural and geometric magnitudes related to the polymer. 

Voltammograms of a polythiophene film showing reasonably reversible electrochemistry of both types are shown in Fig. 2.M The formal potentials (average of the anodic and cathodic peak potentials) for p- and n-doping can provide useful estimates of the energies of the polymer s valence and conduction bands and its band gap35... 

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 ... 

Voltammetry, with electrochemical polymers, 408 Voltammograms anodic, 418... 

In the ideal case, reversible cyclic voltammograms of redoxactive films should show completely symmetrical and mirror-image cathodic and anodic waves with identical peak potentials and current levels 34-i37) pjg... 

Fig. 17. Cyclic voltammogram of the water-soluble Rieske fragment from the bci complex of Paracoccus denitrificans (ISFpd) at the nitric acid modified glassy carbon electrode. Protein concentration, 1 mg/ml in 50 mM NaCl, 10 mM MOPS, 5 mM EPPS, pH 7.3 T, 25°C scan rate, 10 mV/s. The cathodic (reducing branch, 7 < 0) and anodic (oxidizing branch, 7 > 0) peak potentisds Emd the resulting midpoint potential are indicated. SHE, standEU d hydrogen electrode.

The additivity principle was well obeyed on adding the voltammograms of the two redox couples involved even though the initially reduced platinum surface had become covered by a small number of underpotential-deposited mercury monolayers. With an initially anodized platinum disk the catalytic rates were much smaller, although the decrease was less if the Hg(I) solution had been added to the reaction vessel before the Ce(lV) solution. The reason was partial reduction by Hg(l) of the ox-ide/hydroxide layer, so partly converting the surface to the reduced state on which catalysis was greater. 

De Souza et al. (1997) used spectroscopic ellipsometry to study the oxidation of nickel in 1 M NaOH. Bare nickel electrodes were prepared by a series of mechanical polishing followed by etching in dilute HCl. The electrode was then transferred to the spectroelectrochemical cell and was cathodicaUy polarized at 1.0 V vs. Hg/HgO for 5 minutes. The electrode potential was then swept to 0.9 V. Ellipsometry data were recorded at several potentials during the first anodic and cathodic sweep. Figure 27.30 shows a voltammogram for Ni in l.OM NaOH. The potentials at which data were recorded are shown. Optical data were obtained for various standard materials, such as NiO, a -Ni(OH)2, p-Ni(OH)2, p-NiOOH, and y-NiOOH. 

---