**3.1 Thermal Gravimetric Analysis (TGA)**

TGA is frequently used to quantify the amount and thermal stability of PPy in the composite and also to know whether there occurs some interaction between PPy and the other constituent of the composite. The TGA curve of the electrochemically synthesized PPy/chitosan composite on Pt electrode in air showed two stages of the weight loss (Yalcinkaya et al., 2010). The first stage of the thermal degradation was observed at 150- 200ºC and was attributed to removal of the dopant molecule (oxalate ion) from the polymer structure. The decomposition of chitosan chain was indicated by minimum weight loss in temperature range 300-370ºC. On the other hand, the maximum weight loss observed at 380- 400ºC was attributed to the degradation and intrerchain crosslink of the composite. The comparison of results of the PPy/chitosan composite with those obtained from chitosan suggests that an interaction occurs between chitosan and PPy.

Similarly, The TGA analysis of SnO2-PPy nanocomposite from 25 to 700ºC exhibited two weight losses (Cui et al., 2011). The first weight loss, in the temperature range of 25-250ºC, attributed to desorption of physisorbed water, while the second in the range of 250-700ºC, attributed to the oxidation of PPy. Bare SnO2 does not show any weight change in the whole temperature range of the investigation, while the pure PPy is burnt off. So, on the basis of weight change before and after the oxidation of PPy, the SnO2 content in the composite was estimated. TGA analyses of the S/PPy composite, bare S and PPy powder indicated (Wang et al, 2006) that S is burnt completely on temperature up to 340ºC, followed by the oxidation of PPy in the second stage on temperature above 340ºC. The weight loss in the second stage was about 40wt% which represents the amount of PPy in the S-PPy composite. TGA measurements were performed in air. The nanocomposites, SnO2-PPy and S/PPy were prepared by chemical polymerization.

### **3.2 Scanning Electron Microscopy (SEM)**

The morphology of the composite strongly depends upon the nature as well as the method of preparation. From the SEM analyses of pure PPy and its composites it was observed that morphology of the PPy changed significantly when the composite was formed. As, in the case of the PPy/chitosen composite, the SEM image of composite was significantly different compared to that of PPy (cauliflower-like spherical shape) or chitosan (smooth surface) (Yalcinkaya et al, 2010). On the other hand, HRTEM (High Resolution Transmission Electron Microscope) images of pure PPy and graphene nano sheet (GNS)/PPy composite obtained by chemical method (Zhang et.al., 2011) showed that pure PPy has the amorphous structure, while the PPy is homogenously surrounded by GNS in the composite. The particle size of PPy/GNS was found to be smaller than pure PPy.

#### **3.3 X-Ray Diffraction (XRD)**

The XRD pattern of GNS/PPy exhibited diffraction peaks at 2θ ≈ 24.5°, 26° and 42.8º. The diffraction peaks at 2θ ≈ 24.5° and 42.8º correspond to (002) and (100) planes of graphite like structure while that the peak at 2θ ≈ 26º corresponds to amorphous PPy (Zhang et al., 2011). In the GNS/PPy composite, as GNS percentage increased, the broad peak shifted from 2θ ≈ 26º to 24.8º, implying that interaction occurs between GNS and PPy. The Au/PPy core-shell nanocomposites (Liu and Chuang, 2003) displayed a broad maximum at 2θ ≈ 25.1º (d = 3.5 Å) which was ascribed to the closest distance of approach of the planar aromatic rings of Py

Polypyrrole Composites: Electrochemical Synthesis, Characterizations and Applications 139

transition and to the formation of perninfreaniline form (PB) and the spectra of PPy/Cu synthesized in SA and SB indicated a shoulder respectively at 360 and 350 nm, which was

nm which disappeared after addition of Py monomer and a new band of π-π\* transition of PPy appeared in the region 400-500 nm with absorption maximum at 463 nm, showing the formation of Au/PPy nanocomposite with core-shell structure (Liu & Chuang, 2003). The UV-visible absorption spectrum of pure PPy indicated (Konwer et al, 2011) a weaker absorption at 330 nm (π-π\* transition) and stronger absorption at 570 nm (bipolar state of PPy). The PPy/EG (expanded graphite) composite showed a red shift in UV visible spectrum suggesting that EG assists the polymerization in such a way that it maintains a higher conjugation length in the chain of the PPy and there may be possible some coupling between conjugation length of PPy and EG. Estimate of the optical band gap of PPy found by using equation, Egopt (ev) = 1240/λedge(nm), was 2.17 eV, while it decreased to 1.85-1.93

A conductive polymer electrode is a porous material. Various equivalent circuits have been applied to present impedance behavior of the conducting polymer electrodes (Passiniemi & Vakiparta, 1995). But till now, no general equivalent circuit that can satisfy all electrolyteconducting polymer configurations has been reported. In literature, (Levi & Aurabch, 1997, 2004; Lang & Inzelt, 1999; Mohamedi et al., 2001) different equivalent circuit models have been used to treat the experimental data and some of them are given in Fig.3; wherein subscripts 'sl' and 'ct' represent the surface layer and the charge transfer and symbols: Zw, Cint and ZFLW and ZFSW represent Warburg impedance, capacitor due to intercalation and finite length and finite space Warburg type elements, respectively; other symbols have their

Fig. 3. Equivalents circuit (EC) models: (a)Randle`s EC model; (b-d) Modified Randle`s EC (analogs for ion-intercalated electrodes); (e) Meyers EC Model (analog for mixed particle porous electrode); (f) EC model of polymer film electrodes; (g) Voigt and Frumkin and Melik-Gaykazyan (FMG) model (for interfacial boundaries of lithiated graphite electrode).


nano complex showed a band at ~308

assigned to the formation of polybenzoic salt. AuCl4

**3.5 Electrochemical impedance spectroscopy (EIS)** 

eV in PPy/EG with addition of EG.

usual meaning.

like face to face Py rings. However, the XRD of pure PPy film electrodeposited on Au substrate showed the broad maximum at the lower angle, i.e. at 2θ ≈ 19.0º (d = 4.7Å). This may be caused due to scattering from side-by-side Py rings. The estimated values of the coherence length from the Scherrer equation were 11.03 and 9.73Å for Au/PPy nanocomposite and electrodeposited PPy on Au, respectively. The higher coherence value obtained for Au/PPy nanocomposite clearly indicates increased crystallinity and crystalline coherence, which would contribute to the higher conductivity of PPy.

The pure PPy exhibited a broad diffraction peak at 2θ ≈ 24.6°, which is characteristic peak of amorphous like PPy, while the diffraction pattern of PPy/Y2O3 (30wt% oxide) composite was the same as Y2O3 and PPy. It indicated that PPy deposited on the surface of Y2O3 particles has a little effect on crystallization performance of Y2O3 (Vishnuvardhan et al., 2006).

## **3.4 Infra Red (IR)/Raman/UV-visible absorption spectroscopy**

Zhang et al., (2011) recorded the FTIR of pure PPy and PPy/GNS composite and observed that most of peaks, which correspond to PPy, get shifted towards the left when GNS was introduced. This was considered to an association of graphene to the nitrogenous functional group of PPy backbone. The FTIR spectra of PPy-Ag composite showed (Ayad et al., 2009) peaks at 1560 and 1475 cm-1, which correspond to the C-C and C-N stretching vibrations of PPy ring, respectively. The peak position of the composite showed a little shift towards the higher wave number compared to pure PPy. It was probably due to interaction between PPy and Ag particle and improvement of doping level of the polymer.

Raman spectra of PPy/GNS composite exhibited two prominent peaks, at ~1590 (G band) and 1350 (D band) cm-1 which get broadened with increasing amount of GNS in the composite suggesting that the nanocrystalite size decreases due to the phonon confinement (Zhang et al., 2011). A broad peak at 1051 cm-1 and two small peaks at 933 and 981 cm-1 observed for pure PPy and PPy/GNS composite are the characteristic peaks of PPy. In the case of S-PPy composite, peak at ~500 cm-1 corresponds to the S particle and the peak between 800 and 1700 cm-1 corresponds to the PPy nanoparticle suggesting that S-PPy contain both the sulphur (S) and conductive PPy elements (Wang et al., 2006). The Raman spectra of MWCNT exhibited the bands at ~1350 cm-1 (D band) and ~1580 cm-1 (G band), (Fang et. al., 2010). The ratio of D to G band is associated with extent of defect present in the MWCNT and is sensitive to molecular interaction. After PPy deposition D/G ratio decreased which was prominent in short-pulse deposition than that of continuous deposition method. This decrease in D/G ratio is associated with reduction of disorder at the MWCNT surface. Further, Raman spectra of PPy/CNT composite did not produce any additional peaks except the characteristic peaks of CNT and PPy (Kim et al., 2008a). This suggestes that no new chemical bond is formed between CNT and PPy in composite and no chemical change in PPy composite occurs.

UV-visible absorption spectra of the composite PPy-CdS with different CdS contents clearly indicated two absorption bands at 300-400 nm and 700-1000 nm. The former absorption band was assigned to the п-п\* transition and the latter, to the oxidation state of the film. There occurs an increase in absorption of the composite material with CdS concentration, which implies that electronic structure of PPy is affected by CdS (Madani et al., 2011). Sharifirad et al. (2010) prepared PPy on Cu in three aqueous media (citric acid: CA, sodium acetate: SA and sodium benzoate: SB) and recorded their UV-visible specta. The UV spectra of PPy/Cu in CA showed two absorption peaks at 295 and 460 nm, assigned to the π-π\* transition and to the formation of perninfreaniline form (PB) and the spectra of PPy/Cu synthesized in SA and SB indicated a shoulder respectively at 360 and 350 nm, which was assigned to the formation of polybenzoic salt. AuCl4 nano complex showed a band at ~308 nm which disappeared after addition of Py monomer and a new band of π-π\* transition of PPy appeared in the region 400-500 nm with absorption maximum at 463 nm, showing the formation of Au/PPy nanocomposite with core-shell structure (Liu & Chuang, 2003). The UV-visible absorption spectrum of pure PPy indicated (Konwer et al, 2011) a weaker absorption at 330 nm (π-π\* transition) and stronger absorption at 570 nm (bipolar state of PPy). The PPy/EG (expanded graphite) composite showed a red shift in UV visible spectrum suggesting that EG assists the polymerization in such a way that it maintains a higher conjugation length in the chain of the PPy and there may be possible some coupling between conjugation length of PPy and EG. Estimate of the optical band gap of PPy found by using equation, Egopt (ev) = 1240/λedge(nm), was 2.17 eV, while it decreased to 1.85-1.93 eV in PPy/EG with addition of EG.

#### **3.5 Electrochemical impedance spectroscopy (EIS)**

138 Electropolymerization

like face to face Py rings. However, the XRD of pure PPy film electrodeposited on Au substrate showed the broad maximum at the lower angle, i.e. at 2θ ≈ 19.0º (d = 4.7Å). This may be caused due to scattering from side-by-side Py rings. The estimated values of the coherence length from the Scherrer equation were 11.03 and 9.73Å for Au/PPy nanocomposite and electrodeposited PPy on Au, respectively. The higher coherence value obtained for Au/PPy nanocomposite clearly indicates increased crystallinity and crystalline

The pure PPy exhibited a broad diffraction peak at 2θ ≈ 24.6°, which is characteristic peak of amorphous like PPy, while the diffraction pattern of PPy/Y2O3 (30wt% oxide) composite was the same as Y2O3 and PPy. It indicated that PPy deposited on the surface of Y2O3 particles has a

Zhang et al., (2011) recorded the FTIR of pure PPy and PPy/GNS composite and observed that most of peaks, which correspond to PPy, get shifted towards the left when GNS was introduced. This was considered to an association of graphene to the nitrogenous functional group of PPy backbone. The FTIR spectra of PPy-Ag composite showed (Ayad et al., 2009) peaks at 1560 and 1475 cm-1, which correspond to the C-C and C-N stretching vibrations of PPy ring, respectively. The peak position of the composite showed a little shift towards the higher wave number compared to pure PPy. It was probably due to interaction between PPy

Raman spectra of PPy/GNS composite exhibited two prominent peaks, at ~1590 (G band) and 1350 (D band) cm-1 which get broadened with increasing amount of GNS in the composite suggesting that the nanocrystalite size decreases due to the phonon confinement (Zhang et al., 2011). A broad peak at 1051 cm-1 and two small peaks at 933 and 981 cm-1 observed for pure PPy and PPy/GNS composite are the characteristic peaks of PPy. In the case of S-PPy composite, peak at ~500 cm-1 corresponds to the S particle and the peak between 800 and 1700 cm-1 corresponds to the PPy nanoparticle suggesting that S-PPy contain both the sulphur (S) and conductive PPy elements (Wang et al., 2006). The Raman spectra of MWCNT exhibited the bands at ~1350 cm-1 (D band) and ~1580 cm-1 (G band), (Fang et. al., 2010). The ratio of D to G band is associated with extent of defect present in the MWCNT and is sensitive to molecular interaction. After PPy deposition D/G ratio decreased which was prominent in short-pulse deposition than that of continuous deposition method. This decrease in D/G ratio is associated with reduction of disorder at the MWCNT surface. Further, Raman spectra of PPy/CNT composite did not produce any additional peaks except the characteristic peaks of CNT and PPy (Kim et al., 2008a). This suggestes that no new chemical bond is formed between CNT and PPy in composite and no

UV-visible absorption spectra of the composite PPy-CdS with different CdS contents clearly indicated two absorption bands at 300-400 nm and 700-1000 nm. The former absorption band was assigned to the п-п\* transition and the latter, to the oxidation state of the film. There occurs an increase in absorption of the composite material with CdS concentration, which implies that electronic structure of PPy is affected by CdS (Madani et al., 2011). Sharifirad et al. (2010) prepared PPy on Cu in three aqueous media (citric acid: CA, sodium acetate: SA and sodium benzoate: SB) and recorded their UV-visible specta. The UV spectra of PPy/Cu in CA showed two absorption peaks at 295 and 460 nm, assigned to the π-π\*

coherence, which would contribute to the higher conductivity of PPy.

**3.4 Infra Red (IR)/Raman/UV-visible absorption spectroscopy** 

and Ag particle and improvement of doping level of the polymer.

chemical change in PPy composite occurs.

little effect on crystallization performance of Y2O3 (Vishnuvardhan et al., 2006).

A conductive polymer electrode is a porous material. Various equivalent circuits have been applied to present impedance behavior of the conducting polymer electrodes (Passiniemi & Vakiparta, 1995). But till now, no general equivalent circuit that can satisfy all electrolyteconducting polymer configurations has been reported. In literature, (Levi & Aurabch, 1997, 2004; Lang & Inzelt, 1999; Mohamedi et al., 2001) different equivalent circuit models have been used to treat the experimental data and some of them are given in Fig.3; wherein subscripts 'sl' and 'ct' represent the surface layer and the charge transfer and symbols: Zw, Cint and ZFLW and ZFSW represent Warburg impedance, capacitor due to intercalation and finite length and finite space Warburg type elements, respectively; other symbols have their usual meaning.

Fig. 3. Equivalents circuit (EC) models: (a)Randle`s EC model; (b-d) Modified Randle`s EC (analogs for ion-intercalated electrodes); (e) Meyers EC Model (analog for mixed particle porous electrode); (f) EC model of polymer film electrodes; (g) Voigt and Frumkin and Melik-Gaykazyan (FMG) model (for interfacial boundaries of lithiated graphite electrode).

Polypyrrole Composites: Electrochemical Synthesis, Characterizations and Applications 141

The preparation method strongly influences the electrochemical reaction activity of PPy. CVs of PPy films deposited on GC by using three different methods, constant current, constant potential electrolysis and CV, at the scan rate of 100 mV/s in the potential region from -0.20 to 1.02 V vs. Ag/AgCl in 0.1M PBS (Phosphate buffer saline) have shown that the galvanostatically deposited polymer film had the greatest electrochemical activity than that of potentiostatically deposited film. A triple lyer of PPy films on the GC electrode, obtained by sequential electrodeposition method, has the worst redox capacity (Lee et al., 2005). The charge transport properties in the PPy matrix depends upon the nature and concentration of the doping anions. The charge transport properties of a triple lyer of PPy films on the GC electrode, obtained by sequential electrodeposition method, were examined by CV under Ar

¯, ClO4

mVs-1 from -0.8 to +0.8 V/SCE (Nguyen Cong et al., 2005). The changes in shape and characteristics of CVs were observed with doping anions. For instance, the increase of the

current intensities. In fact, in its oxidized state the PPy incorporates the doping anions in order to neutralize the positive charges (dications, i.e. bipolaron) created on its backbone by the electropolymerization process. The switching between the oxidized and reduced states implies the deintercalation/intercalation of these anions, whose ability to move depends on their

Recently, CVs of sandwich-type electrodeposited composite films of PPy and CoFe2O4 on graphite (G) having structure G/PPy/(PPy(CoFe2O4)/PPy in Ar-deoxygenated 0.5 M KOH containing K2SO4 as a dopant anion indicated a broad anodic and a broad cathodic maxima corresponding to establishment of the redox couple,[PPy+. SO42-]/[PPy + SO42-] (Singh et al., 2004), transport of doping anion being a diffusion controlled one. Features of CVs of pure PPy and composite electrodes were similar. Similar results were also found from the study of CVs of similar sandwich type composites of PPy with LaNiO3 (Singh et al., 2007b), La1 xSrxMnO3 (0≤x≤0.4) (Singh et al., 2007a), Cu1.4Mn1.6O4 (Nguyen Cong et al., 2002a), NixCo3-

Very recently, CVs of nanocomposite systems, MnO2/PPy, SO42- (Sharma et al, 2008), PPyCl (PPy films doped with Cl¯), Cl¯ and PPyClO4 (PPy films doped with ClO4¯), ClO4¯ (Sun et al.,

that the specific capacitance of composites are greatly enhanced in comparison with those obtained for their respective constituents elements/materials. Further, the CV curves of PEDOT/h-PPy and PPy doped with ClO4¯ have rectangle like (i.e. ideal) shapes while CV

Conductive polymers are presently being considered as potential materials for corrosion protection of metals. They can substitute conventional protection materials such as chromates and phosphates used in the electroplating and paint industries with stronger more resistant and environmentally friendly coatings. The traditional anticorrosion materials provide

A conductive organic coating forms a physical barrier against corrosive agents and a passive layer on the metal surface. The corrosion protection efficiency of this organic coating can be

excellent corrosion protection coatings but their toxicity has been severely questioned.

curves for MnO2/PPy, PPy doped with Cl¯ and PEDOT/c-PPy are non ideal.

¯, NO3

¯, SO4


¯ (520 mV/SCE) is accompanied by a drop in the peak

2-) solution at a scan rate of 10

¯ (440

¯ (380 mV/SCE) < PF6

(Wang et al., 2007) have shown

atmosphere in Py-free 0.15M KA (A = Cl¯, PF6

mV/SCE < NO3

**4. Applications** 

**4.1 Corrosion protection coatings** 

anodic peak potential (Epa) in sequence Cl¯ (150 mV/SCE) < ClO4

¯ (490 mV/SCE) < SO4

nature. This explains the changes in shape of the CVs.

xO4 (x = 0.3 and 1.0) (Nguyen Cong et al., 2002b).

2009) and PEDOT/c-PPy, ClO4¯ and PEDOT/h-PPy, ClO4

The EIS spectra (i.e. Nyquist plots) of several composites such as S/T-PPy (Tubular PPy) and S/G-PPy (Granular PPy) (Liang et al., 2010), PEDOT/h-PPy (Poly 3,4 ethylenedioxythiophene/horn like-PPy) (5:1) (Wang et al., 2007), PPy films on DuPont 7012 carbon composite (Li et al., 2005), S-PPy(Wang et al., 2006) and Si/PPy (9:1) (Guo et al. 2005) reported in literature displayed a small semi-circle at high frequencies and a straight line at lower frequencies. The observed linearity at low frequencies has been ascribed to the anion diffusion in the composite matrix and the semicircle in the high frequency region, to the contact resistance and charge transfer resistance. Only in the case of PEDOT/h-PPy, a line indicating a capacitive behavior related to the film charging mechanism at low frequencies was observed.

The EIS study of sandwich-type composite film electrodes of PPy and a mixed valence oxide have generally produced more or less similar Nyquist plots. Each Nyquist curve indicated a capacitive behavior at low frequencies, a small semicircle (or an arc) at high frequencies and more or less a linear curve at intermediate frequencies. The observed semicircle at high frequencies is considered to be produced due to contribution of the charge transfer reaction (Singh et al., 2004). In some cases, no semicircle corresponding to the charge transfer reaction is observed (Malviya et al., 2005; Singh et al., 2007a); in these cases the charge transfer resistance is thought to be much smaller than the sum of the film and solution resistances. In fact, at higher frequencies, the diffusion of anions (ClO4 ¯, Cl¯ or SO4 2-) into the polymer matrix dominates the impedance results and that a conventional semi-infinite Warburg response is observed. At relatively lower frequencies, the ∆Zim/∆Zreal value increases with decreasing frequency and that the impedance response results a capacitivetype behavior. Thus, a change over seems to take place from the semi-infinite Warburg regime to the finite Warburg regime with the variation of frequency from high (100 KHz) to to a low value (20 mHz).

The spectra obtained were analyzed by fitting the equivalent circuits, Rs(RQ)Q', Rs(R1Q1)(R2C2)(R3C3)C4W4, RsQWC, LR(RQ)(RQ)Q and LR(RQ)(RQ), where Rs is solution resistance, Q is constant phase elemnt, W is Warburg resistance and C is capacitance.The apparent diffusion coefficient (Da) for transport of anions particularly SO4 2- in the polymer matrix were also estimated at varying potentials. Estimates of Da values for SO42- anions at a constant potential, E = -0.1 V vs SCE in deoxygenated 0.5M K2SO4 + 5mM KOH at 25°C were 1.1, 12.1, 2.5, 0.7, 0.60 × 10-7 cm2 s-1 in binary composites of PPy and LaNiO3, LaMnO3, La0.8Sr0.2MnO3, La0.7Sr0.3MnO3 and La0.6Sr0.4MnO3, respectively.

#### **3.6 Cyclic Voltammetry (CV)**

During the CV, the PPy film electrode-electrolyte system involves the redox couple, PPy+/ PPy (Kaplin & Qutubuddin, 1995), where PPy is the neutral species (associated with three to four monomer units) and PPy+ is the radical cationic species or polaron (one positive charge localized over three to four monomer units). In the oxidized state, the PPy is positively charged and so, some anions get migrated from solution into the polymer matrix so as to maintain electroneutrality. Similarly, on reduction, as electrons are injected and the positive charge on the polymer chain disappears, some anions leave the PPy matrix and enter into the solution. The formation of a second redox couple, PPy++/ PPy+, has also been proposed (Genies and Pernaut, 1985) to explain two reduction peaks observed in some CVs. PPy++ is the dicationic species or bipolaron. The counterion concentration will be greater for a PPy film containing both polaron and bipolaron species than for a film containing only polaron species (Kaplin and Qutubuddin, 1995).

The preparation method strongly influences the electrochemical reaction activity of PPy. CVs of PPy films deposited on GC by using three different methods, constant current, constant potential electrolysis and CV, at the scan rate of 100 mV/s in the potential region from -0.20 to 1.02 V vs. Ag/AgCl in 0.1M PBS (Phosphate buffer saline) have shown that the galvanostatically deposited polymer film had the greatest electrochemical activity than that of potentiostatically deposited film. A triple lyer of PPy films on the GC electrode, obtained by sequential electrodeposition method, has the worst redox capacity (Lee et al., 2005).

The charge transport properties in the PPy matrix depends upon the nature and concentration of the doping anions. The charge transport properties of a triple lyer of PPy films on the GC electrode, obtained by sequential electrodeposition method, were examined by CV under Ar atmosphere in Py-free 0.15M KA (A = Cl¯, PF6 ¯, ClO4 ¯, NO3 ¯, SO4 2-) solution at a scan rate of 10 mVs-1 from -0.8 to +0.8 V/SCE (Nguyen Cong et al., 2005). The changes in shape and characteristics of CVs were observed with doping anions. For instance, the increase of the anodic peak potential (Epa) in sequence Cl¯ (150 mV/SCE) < ClO4 ¯ (380 mV/SCE) < PF6 ¯ (440 mV/SCE < NO3 ¯ (490 mV/SCE) < SO4 ¯ (520 mV/SCE) is accompanied by a drop in the peak current intensities. In fact, in its oxidized state the PPy incorporates the doping anions in order to neutralize the positive charges (dications, i.e. bipolaron) created on its backbone by the electropolymerization process. The switching between the oxidized and reduced states implies the deintercalation/intercalation of these anions, whose ability to move depends on their nature. This explains the changes in shape of the CVs.

Recently, CVs of sandwich-type electrodeposited composite films of PPy and CoFe2O4 on graphite (G) having structure G/PPy/(PPy(CoFe2O4)/PPy in Ar-deoxygenated 0.5 M KOH containing K2SO4 as a dopant anion indicated a broad anodic and a broad cathodic maxima corresponding to establishment of the redox couple,[PPy+. SO4 2-]/[PPy + SO4 2-] (Singh et al., 2004), transport of doping anion being a diffusion controlled one. Features of CVs of pure PPy and composite electrodes were similar. Similar results were also found from the study of CVs of similar sandwich type composites of PPy with LaNiO3 (Singh et al., 2007b), La1 xSrxMnO3 (0≤x≤0.4) (Singh et al., 2007a), Cu1.4Mn1.6O4 (Nguyen Cong et al., 2002a), NixCo3 xO4 (x = 0.3 and 1.0) (Nguyen Cong et al., 2002b).

Very recently, CVs of nanocomposite systems, MnO2/PPy, SO42- (Sharma et al, 2008), PPyCl (PPy films doped with Cl¯), Cl¯ and PPyClO4 (PPy films doped with ClO4 ¯), ClO4 ¯ (Sun et al., 2009) and PEDOT/c-PPy, ClO4¯ and PEDOT/h-PPy, ClO4 - (Wang et al., 2007) have shown that the specific capacitance of composites are greatly enhanced in comparison with those obtained for their respective constituents elements/materials. Further, the CV curves of PEDOT/h-PPy and PPy doped with ClO4¯ have rectangle like (i.e. ideal) shapes while CV curves for MnO2/PPy, PPy doped with Cl¯ and PEDOT/c-PPy are non ideal.
