Polypyrrole cyclic voltammogram

Figure 4 compares cyclic voltammograms for a redox polymer (poly-[Fe(5-amino-1,10-phenanthroline)3]3+/2+)91 and p-doping and undoping of a conducting polymer (polypyrrole).92 The voltammogram for the redox... 

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.]...

Figure 18. Cyclic voltammograms of a polypyrrole film in propylene carbonate containing 0.5 M UCIO4.97...

If the film is nonconductive, the ion must diffuse to the electrode surface before it can be oxidized or reduced, or electrons must diffuse (hop) through the film by self-exchange, as in regular ionomer-modified electrodes.9 Cyclic voltammograms have the characteristic shape for diffusion control, and peak currents are proportional to the square root of the scan speed, as seen for species in solution. This is illustrated in Fig. 21 (A) for [Fe(CN)6]3 /4 in polypyrrole with a pyridinium substituent at the 1-position.243 This N-substituted polypyrrole does not become conductive until potentials significantly above the formal potential of the [Fe(CN)6]3"/4 couple. In contrast, a similar polymer with a pyridinium substituent at the 3-position is conductive at this potential. The polymer can therefore mediate electron transport to and from the immobilized ions, and their voltammetry becomes characteristic of thin-layer electrochemistry [Fig. 21(B)], with sharp symmetrical peaks that increase linearly with increasing scan speed. 

Figure 21. Cyclic voltammograms (at 20to lOOmVs-1)of [FefCNJd3"74-electrostatically trapped in polypyrrole films with an alkyl pyridinium substituent at the (A) 1 - or (B) 3-position.243 (Reprinted with permission from J. Phys. Chem. 96, 5604-5610, 1992 Copyright 1992, American Chemical Society.)...

Cyclic voltammetric studies involving polymers, 558 and the nature of charge carriers, 561 and the nucleation loop, 557 of poly (3-methylthiophene), 564 and parallel-band electrodes, 570 Cyclic voltammograms as a function of scan rate, 559 involving polymerization, 559 with polyanaline, 566 of polypyrrole film, 581... 

Fig. 7. Cyclic voltammograms for the oxidation of polyacetylene (PA), polypyrrole (PPy) and polyqnaterthienyl (PQTh)...

Fig. 19. Cyclic Voltammograms of [Pt]polypyrrole (20 nm thick) in CH3CN containing various electrolyte salts. Sweep rates 50 and 100 mVs 1. Reproduced from [262].

Dynamic properties. On the basis of cyclic voltammetry, Diaz et al. (1981) showed that thin films of polypyrrole on an electrode immersed in acetonitrile could be repeatedly driven between the conducting and insulating states, as shown by the stability of the cyclic voltammograms of the films (see Figure 3.73). 

Figure 3.74 Cyclic voltammograms of a 20nm-thick polypyrrole film on Pt in CHjCN containing different electrolytes. Two sweep rates are shown, the voltammograms showing the tower currents were taken at 50mVs , and the larger currents were obtained at lOOmVs"...

Typical voltammograms of a polypyrrole him obtained by the authors are shown in Figure 3.81. If the film was held at —0.6 V vs. SCE prior to cycling, the cyclic voltammogram showed a definite peak, near c. - 0.15 V, as was observed by other workers and is discussed above. The potential at which this peak occurs was found to mark a definite transition point in the behaviour... 

Figure 3.81 Typical cyclic voltammograms of a poly pyrrole film on Pt in Nrsatu rated 1 M NaClOj. The voltammograms were collected immediately after holding the film at -0.6 V vs, SCE for 5 min and after cycling for 5 min. The scan rate was 100 mV s "1 and the film thickness 84 nm. Reprinted from Electrochimica Acta, 36, P.A, Christensen and A. Hamnett, In situ Spectroscopic Investigations of the Growth, Electrochemical Cycling and Overoxidation of Polypyrrole in Aqueous Solution , pp. 1263-1286(1991), with kind permission from Pergamon Press Ltd., Headington Hill Hall, Oxford OX3 0BW, UK.

Thus, it appears that the transition represented by the anodic peak in the cyclic voltammogram of polypyrrole is due to a changeover in the dominant carrier type and is accompanied by a dramatic contraction of the film. The authors strongly suspected that this contraction was due to electro-striction associated with bipolaron formation. As a further test they also carried out experiments intended to test if proton expulsion from the film occurred on oxidation. They found that it did indeed occur but monotonically at alt potentials > -0.6 F, in agreement with the extremely elegant work of Tsai et at. (1987), and so could not be responsible for the relatively sudden contraction at potentials > —0.2 V. 

Polypyrrole Film Formation in Glucose Oxidase Enzyme Solution. Cyclic voltammograms recorded in the GOD and pyrrole solution showed an anodic peak current (E = 1.08 V), which suggested the polymerization of pyrrole in the above solution. However, the polymerization potential moved toward the more positive direction compared to the polymerization potential of PPy doped with Cl ( pa < 1.0 V). This is due to the fact that the polymerization is more difficult to take place in enzyme solution than in Cl solution because the enzyme solution is a much weaker electrolyte than NaCl it may also be due to the less conductive nature of the PPy-GOD film as compared to that of the PPy-Cl film. The polymerization current level was much lower in the enzyme solution than in the Cl solution because of the poor charge-transport property of the enzyme protein molecules. It was found that the constant current method was more suitable than the controlled potential method for making the PPy-GOD film on the GC electrode. 

Fig. 11.13. Cyclic voltammograms of 5 m/Wquinone-hydroquinone and polypyrrole-/> toluene sulfonate, (a) pH 1, (b) pH 3, and (c) pH 5. (Reprinted from D. L. Miller and J. O M. Bockris, Structure of the Polypyrrole/Solution Interphase, J. Electrochem. Soc. 139 970-975,1992. Reproduced by permission of The Electrochemical Society, Inc.)...

Zhou et al. reported template-synthesized cobalt porphyrin/polypyrrole (TPPS-Co/PPy) nanocomposite and its electrocatalysis of oxygen reduction in a phosphate buffer solution (PBS) [97]. With the assistance of ultrasonication and different preparation procedures, the nanocomposite can be electrochemicaUy synthesized with uniform 2-D and 3-D nanostructures. Lines (a) and (b) of Figure 17.8 show the cyclic voltammograms of a cobalt... 

Figure 17.8 Cyclic voltammograms of (a) the TPPS-Co/PPy nanocomposite-coated electrode in the 02-saturated PBS (solid line) (b) the TPPS-Co/PPy nanocomposite-coated electrode in the N2-saturated PBS, and (c) the bare Au electrode in the 02-saturated PBS scan rate is 50 mV s (Reprinted with permission from Journal of Physical Chemistry C., Template-Synthesized Cobalt Porphyrin/Polypyrrole Nanocomposite and Its Electrocatalysis for Oxygen Reduction in Neutral Medium by Qin Zhou, Chang Ming Li, Jun Li et a ., 111, 30, 11216-11222. Copyright (2007) American Chemical Society)...

Fig.3. Cyclic voltammograms obtained for a polypyrrole-anti-HSA electrode generated galvanostatically at a platinum electrode from a solution of 0.5 M pyrrole that was 100 ppm in anti-HSA. Dotted line represents scan for polypyrrole-anti-HSA electrode cycled in 0.1 M NaNOs, whereas solid lines represent subsequent scans in 0.1 M NaNOs that was 100 ppm in HSA (conditions scan rate lOOmV/s).

Figure 11.19 High frequency part of capacitance and resistance of a polypyrrole film as function of the potential. The film was prepared by anodic oxidation in a perchlorate electrolyte. Additionally, the cyclic voltammogram is shown. The film has metal-like properties at positive potentials (E> OV) and neutral state properties at negative potentials (E < -0.5 V).

FIGURE 6.14. Experimental cyclic voltammograms for a 1 -//m-thick polypyrrole film in 1 mol.dm ... 

FIGURE 7.6. Typical cyclic voltammograms of a polypyrrole film on a platinum foil electrode in N2-saturated IM NaC104. Voltammograms were collected immediately after holding the film at-0.6 V for 5 minutes and cycling for 5 minutes scan rate 100 mV/s, film thickness 84nm. (From Ref 20)... 

FIGURE 18.3 Comparison of cyclic voltammograms of polypyrrole (PPy) films in classical electrolyte and ionic liquids. Scan rate 100 mVs . (Reprinted from Pringle, J.M., J. Efthimiadis, PC. Howlett, D.R. MacFarlane, A.B. Chaplin, S.B. Hall, D.L. Officer, G.G. Wallace, and M. Forsyth. Polymer, 45,1447-1453, 2004. With permission.)... 

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