Oxidative degradation pathway of polyaniline film electrodes

Polyaniline (PAn) is an electrically conducting polymer that can be easily prepared by the chemical and electrochemical oxidation of aniline, and shows excellent stability under ambient conditions. Electrochemical synthesis is generally carried out on metal electrodes in aqueous acidic solutions, such as HClO 4 , HCl and H 2 SO 4 , using potentiostatic, galvanostatic and potential cycling methods. A large number of studies on the redox process of PAn have been performed by means of electrochemical and optical techniques, revealing that electron transfer causes the migration of electrolyte ions into or out of the polymer film. 1 However, the scheme of electropolymerization of aniline, involving the charge-compensation manner, is not well understood. A film prepared from HClO 4 is known to be denser than that from H 2 SO 4 , suggesting that the electrolyte anion plays an important role in the polymerization of aniline. 2,3 According to the reaction scheme proposed by Mohilner et al., polymerization starts by the oxidation of non-protonated aniline to radical cationic species, and proceeds through coupling with another radical; these reactions are accompanied by the release of protons to eliminate the generated positive charges. 4 This suggests that the acidity at the polymer/solution interface increases during the course of aniline oxidation, but the effect of accumulated protons on the rate of polymerization is not determined. Furthermore, side reactions, such as degradation of the polymer, are not negligible during prolonged polymerization. 5 An in situ spectroelectrochemical method is useful to study such unclear problems.In the present study, in situ FTIR spectroscopy was applied to the electrochemical polymerization of aniline, and the growing polymer and polymer/solution interface were investigated on the molecular level. In situ FTIR spectroscopy has proven to be fruitful for studies on the metal/solution interface 6 and an electroactive film.7 An advantage of this technique when used in the latter system is that it allows a simultaneous determination of the polymer structure and movement of electrolyte species through the film. ExperimentalAll chemicals were of reagent grade and used as received. Sulfuric and perchloric acid solutions used as the electrolytes were prepared with those chemicals and doubly distilled water, and higher pH values were adjusted by adding a concentrated NaOH solution.The FTIR spectrometer used was a Shimadzu FTIR 8100M equipped with an external-reflection unit and a HgCdTe (MCT) detector cooled with liquid nitrogen. The spectroelectrochemical cell was similar to that described elsewhere. 8 A flat CaF 2 disk was used as the IR transparent window, and the angle of incidence on the CaF 2 surface was 70˚. Spectroelectrochemical experiments were carried out with a Pt disk (area=0.50 cm 2 ) substrate. The Pt surface was polished to a mirror finish with 0.3 µm alumina paste and sonicated for 10 The electrochemical polymerization of aniline on a platinum electrode in aqueous HClO4 and H...

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“…This conclusion can be represented by Scheme 1, which is consistent with that proposed based on the electrochemical results. 5,20 …”

Section: Oxidative Degradation Of Panmentioning

confidence: 99%

In Situ Observation of Electrochemical Formation and Degradation Processes of Polyaniline by Fourier-Transform Infrared Spectroscopy

1999

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“…In neutral and acid medium this range goes up to ca.1.8 V vs Ag|AgCl. At this highly anodic potential, oxidative degradation of the polymeric film and its irreversible spoilage occurs 44,45 .…”

Section: Introductionmentioning

confidence: 99%

Poly-0-Aminophenol Obtained at High Potentials by Cyclic Voltammetry on Sn0(2): F Electrodes: Application in Quantitative Determination of Ascorbic Acid

Armijo

Canales

Río

et al. 2009

J. Chil. Chem. Soc.

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In the present work the obtention of poly-o-aminophenol (POAP) at high potentials on conducting glass (SnO 2 : F) is reported. The synthesis was carried out by continuous potential cycling in a 1×10 -3 M o-aminophenol (OAP), 0.1 M hydrochloric acid, and 0.1 M potassium chloride solution between -0.2 and 1.5 V at 0.05 V·s -1 vs Ag│AgCl. The polymer growth was followed by cyclic voltammetry, UV-vis spectra, and AFM characterization. The SnO 2 : F modified electrode (SnO 2 : F/POAP) was tested in the electro-oxidation of ascorbic acid (AA) in phosphate buffer solution. This coating showed an important electrocatalytic effect because a negative anodic shift of 0.4 V with respect to a bare SnO 2 : F glass electrode was observed.

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“…PANI also has very good environmental stability and good redox reversibility [1,2]. Low cost and wide availability of aniline and its derivatives marked PANI as an ideal candidate in various applications such as electrochimic devices [3,4], light-emitting diodes [5], gas and pH sensing [6][7][8][9], and many others. Thin films from PANI polymer are frequently studied form of PANI on different substrates and with different techniques of preparations [10].…”

Section: Introductionmentioning

confidence: 99%

Formation and Implementation of PANI Thin Film Polymerization

Shukla¹

2018

IJRASET

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Polyaniline (PANI) is one of the most studied and applied conducting polymers because of the unique conduction mechanism and high environmental stability. PANI could be synthetized by chemical or electrochemical methods. For this study PANI thin films deposited on glass substrate were prepared by chemical bath deposition from anilinium sulfate (precursor) using ammonium peroxodisulfate as strong oxidizing agent. Prepared samples were dried in high voltage static electric field (0.6 -2.7 kV/cm). The most important effect was the increase of PANI thin film conductivity. Results showed changes in the microstructure, morphology, and conductivity of PANI thin films in dependence on high voltage electrical field. Optical transmittance was studied by UV-VIS spectroscopy and Raman microspectroscopy was used to study structural changes in PANI chains. Variances in the range 1480-1650 cm-1 was revealed in Raman spectra. The dependence of conductivity on electric field intensity showed the maximum for samples dried in field of intensity 1.0 kV/cm. This conductivity was 374 S/m. Presented results show the possibility to change the structure properties of PANI thin films using high voltage static electrical field.

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Oxidative degradation pathway of polyaniline film electrodes

Cited by 384 publications

References 7 publications

In Situ Observation of Electrochemical Formation and Degradation Processes of Polyaniline by Fourier-Transform Infrared Spectroscopy

In Situ Observation of Electrochemical Formation and Degradation Processes of Polyaniline by Fourier-Transform Infrared Spectroscopy

Poly-0-Aminophenol Obtained at High Potentials by Cyclic Voltammetry on Sn0(2): F Electrodes: Application in Quantitative Determination of Ascorbic Acid

Formation and Implementation of PANI Thin Film Polymerization

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