An insight into the overoxidation of polypyrrole materials

Debiemme‐Chouvy, Catherine; Tran, Mai T.T.

doi:10.1016/j.elecom.2008.04.024

Cited by 90 publications

(72 citation statements)

References 26 publications

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“…[20] It has been reported that when only anions of weak acids (named weak-acid anions), such as monohydrogenophosphate, acetate, carbonate, monohydrogenocarbonate or tartrate ions, which confer a relatively high pH to the Py solution, are present in a pyrrole aqueous solution the electrooxidation of the monomers leads to a pinhole conductive overoxidized polypyrrole (OPPy) film, under potentiostatic or potentiodynamic conditions. [21,22] at the film/solution interface, when the anion concentration begins to increase, due to the anion diffusion from the electrolyte bulk and polymer dedoping (anions are expelled from the polymer when it is overoxidized), PPy nanowires start to grow at the places where O 2 has been formed during step 2.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of formation of templateless electrogenerated polypyrrole nanostructures

Fakhry

Cachet

Debiemme‐Chouvy

2015

Electrochimica Acta

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To cite this version:Ahmed Fakhry, Hubert Cachet, Catherine Debiemme-Chouvy. Mechanism of formation of templateless electrogenerated polypyrrole nanostructures. Electrochimica Acta, Elsevier, 2015, 179, pp.297-303 AbstractIn the presence of a high concentration of weak-acid anions, such as monohydrogenophosphate which confer to a pyrrole aqueous solution a pH around 9, an ultra thin non-conductive overoxidized polypyrrole film is deposited on the electrode under an anodic polarization. In the same experimental conditions, after addition of perchlorate anions (C > 0.5 mM) in the pyrrole solution the electrooxidation of the monomers leads to the synthesis of a superhydrophilic nanostructured conductive polypyrrole film (network of nanofibers or oriented nanowires, 50-120 nm in diameter).The aim of the present paper is to confirm the mechanism that we have previously proposed and so to explain the spontaneous nanostructuration of the electrogenerated polypyrrole films. We have assumed that this templateless formation of nanostructures is notably due to the oxidation of water with production of hydroxyl radicals and nanobubbles of dioxygen. Due to the fact that pyrrole polymerization is associated to the release of protons, we have first verified that the electrode/solution interfacial pH is compatible with the water oxidation potential. For this purpose, during the monomer oxidation the interfacial pH variation has been monitored using a pH electrode having a flat glass membrane which was covered with a Pt grid used as the working electrode. Secondly, the presence of dioxygen nanobubbles has been indirectly confirmed by rotating the working electrode. Indeed rotation of the electrode allows eliminating the nanobubbles present inside the polypyrrole film. For the highest rotation speed tested (94 rad s -1 ), a very thin overoxidized film was electrogenerated. Our results are in good agreement with the fact that the nanobubbles protect the PPy film against the action of the hydroxyl radicals which react with the polypyrrole film leading to its overoxidation.

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Section: Introductionmentioning

confidence: 99%

Mechanism of formation of templateless electrogenerated polypyrrole nanostructures

Fakhry

Cachet

Debiemme‐Chouvy

2015

Electrochimica Acta

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“…23 For electrochemical PPy synthesis, various parameters such as the applied potential or the anodic current, 24 the concentration of monomer, 25 the nature of the supporting electrolyte, 26 and the nature of the working electrode 27 have an influence on the growth kinetics and the final structure of the polymer. 28,29 Polypyrrole nanostructures have been obtained using pyrrole solution containing either monohydrogenophosphate 28 or mixing of monohydrogenophosphate and dihydrogenophosphate (phosphate buffer solution (PBS)) [30][31][32][33][34][35] or carbonate. 36,37 For example, it has been shown that in the presence of only monohydrogenophosphate or carbonate anions, ultra thin overoxidized PPy films are formed.…”

Section: Introductionmentioning

confidence: 99%

Templateless electrogeneration of polypyrrole nanostructures: impact of the anionic composition and pH of the monomer solution

2014

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Different superhydrophilic polypyrrole nanostructures can be electrosynthezised in the presence of anions of weak acid (monohydrogenophosphate) and non-acidic anions (perchlorate) without the need for templates. Actually the type of nanostructures formed depends both on the concentration of anions at the electrode and on the interfacial pH. Depending on the anion composition of the pyrrole aqueous solution the film electrogenerated under a given applied potential is either a very thin membrane (10-20 nm) consisting of overoxidized polypyrrole or a tridimensional film with oriented nanowire array or a network of more or less interconnected nanofibers. The formation of such nanostructures is explained by a side reaction which is water oxidation. Since this reaction is pH-dependent, the pH of the pyrrole solution is one of the key parameter for the synthesis of such nanostructures. The reaction mechanism is discussed and compared to those proposed in the literature for nanofiber network electrosynthesis.Actually in the monomer solution, the role of the anions of weak acid is twofold. On the one hand they allow to limit the decrease of the interfacial pH during pyrrole oxidation and on the other hand to decrease the interfacial anion concentration, so that water oxidation takes place with formation of hydroxyl radicals and dioxygen nanobubbles.

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“…7,8 The presence of strong nucleophiles such as OH -leads to the formation of quinone moieties that disrupt the conjugated backbone thereby affecting the electronic and redox properties of PPy. 9 The positive charge obtained on the polypyrrole during polymerization is often compensated by incorporation of anion in the polymer matrix. Hence the properties of PPy largely depend on the kind of dopant anion used during synthesis.…”

Section: Introductionmentioning

confidence: 99%

“…9,12 The degradation study on PPy has been performed using voltammetric and chronoamperometric techniques. 8 Mostany et al 13 have found that the overoxidation affects the ionic and electronic transport properties of the polymer leading to irreversible degradation of the electroactive properties of the material.…”

Section: Introductionmentioning

confidence: 99%

Effect of p‐toluenesulfonate on inhibition of overoxidation of polypyrrole

Kumar

Singh

Agarwal

et al. 2013

J of Applied Polymer Sci

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Electrochemically synthesized polypyrrole (PPy) films degrade under anodic polarization in aqueous solution. PPy is irreversibly oxidized leading to subsequently to an insulating material. This article highlights the degradation behavior of electrochemically synthesized PPy films using inorganic (perchlorate, ClO 4 À ), organic (p-toluenesulfonate, pTS À ) and mixed (inorganic-organic,anions systems in aqueous solution. The PPy films were subject to overoxidation by means of anodic polarization for a certain period of time and consecutively cyclic voltammetry and electrochemical impedance spectroscopy were employed to investigate the influence of anions used during polymerization on the stability and redox activity of the polymer. The modification in the surface morphology of PPy films due to the application of anodic polarization distinctively shows the effect of degradation at polymer/electrolyte interface. The presence of organic anion in the system (PPy/pTS and PPy/mixed) has shown improved electrochemical activity and is stable to electrochemical degradation for a longer period of time than PPy/ClO 4 À .

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An insight into the overoxidation of polypyrrole materials

Cited by 90 publications

References 26 publications

Mechanism of formation of templateless electrogenerated polypyrrole nanostructures

Mechanism of formation of templateless electrogenerated polypyrrole nanostructures

Templateless electrogeneration of polypyrrole nanostructures: impact of the anionic composition and pH of the monomer solution

Effect of p‐toluenesulfonate on inhibition of overoxidation of polypyrrole

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