Conducting polymers voltammogram

Figure 4. Log intensity vs. potential plots (Tafel plots) obtained from the voltammograms of a platinum electrode submitted to a 2 mV s l potential sweep polarized in a 0.1 M LiC104 acetonitrile solution having different thiophene concentrations. (Reprinted from T. F. Otero and J. Rodriguez, Parallel kinetic studies of the electrogeneration of conducting polymers mixed materials, composition, and kinetic control. Electrochim, Acta 39, 245, 1994, Figs. 2, 7. Copyright 1997. Reprinted with permission from Elsevier Science.)...

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. 

From Eq. (68), following a procedure similar to that described for chronoamperograms and voltammograms, theoretical coulovoltagrams were obtained as a function of the variables studied. The results189 can be observed in Fig. 67. Some new effects can be deduced from these experimental curves, which will allow us to provide a complete description of the electrochemistry of conducting polymers. 

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.]...

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 ... 

The conducting polymers show a significant non-faradaic component of the electrochemical mechanism. The essential differences of faradaic and non-faradaic systems in equilibrium behavior, trends of galvanostatic charge - discharge curves and cyclic voltammograms have been shown, and criteria for the identification of these mechanisms are proposed [8],... 

The broad nature of the current peaks in the voltammogram of conducting polymers such as poly pyrrole has been interpreted in a number of w one of which was to attribute it to the movement of anions across the polymei, electrolyte interface, a vital process if the overall charge neutrality of the film is to be maintained. The participation of the electrolyte in the electrochemistry of the polymer film is easily seen by comparing the response of polypyrrole in a variety of different electrolytes (see Figure 3.74). 

Representative voltammograms for the polymerisation of aniline/AChE at sonochemically fabricated templates showed that aniline may be polymerised under acidic conditions to form a conducting polymer that... 

Besides methanol and ethanol, only a few other small molecules (HCOOH, HCHO, CO), have been oxidized at electron conducting polymer electrodes modified by incorporation of platinum microparticles. The first study on formic acid oxidation at Pt particles dispersed in a PAni matrix was carried out, as early as 1986, by Gholamian et al. [57], They found that the incorporation of 100 pg cm of Pt into PAni was sufficient to enhance considerably the oxidation rate of formic acid (ten-fold increase). The cyclic voltammograms recorded with 0.5 M HCOOH in 0,5 M H2SO4 displayed an enhanced oxidation current particularly for the first oxidation peak at 0.2 V/SCE, attributed to the oxidation of the weakly adsorbed intermediate (reactive species). The second peak, at 0.6 V/SCE, attributed to the oxidation of the strongly chemisorbed... 

An alternative model uses the Crank-Nicholson method to generate a voltammogram that consists of a layer with a series of microscopic formal potentials, most situated at O.OV and the rest equally spaced 50 mV apart. This also yields a voltanmiogram (Fig. 6.16) similar to the experimental one (Fig. 6.14). The basis for this is the fact that different oligomers of different chain length possess a range of redox potentials. Thus at least qualitatively, two models may account for the electrochemical behavior of a conducting polymer coated on an electrode. 

Figure 2.21 Electrochromic switching behavior of glass/FTO/WO /ion-conductive-polymer-membrane/Niji jO/PANI/FTO/glass device (a) cychc voltammograms after the 50th and 300th cycles between -0.8 and +1.7 V at scan rate 20 m V/s (b) chronocoulometry curves and optical transmittance changes at X = 480 nm measured after 201 switches between -1.7 and +1.0 V and (c) the in situ optical spectra for bleached and colored states measured after 201 switches between -1.7 and +1.0 V and corresponding coloration efficiency. Reprinted with permission from [233]. Copyright (2012) Elsevier.

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