Electrochemical Properties of Poly-o-Phenylenediamine Films in Solutions with Variable Concentration of Hydronium Ions (original) (raw)
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Charge transfer processes at poly-o-phenylenediamine and poly-o-aminophenol films
Electrochimica Acta, 2005
A comparative study of charge transfer at electrodes modified with the title polymer films was performed mainly in 1 M perchlorate solutions at variable pH by using different electrochemical methods. Experiments with Nafion ® -coated electrodes were carried out to elucidate the role of the supporting electrolyte anions, also exploiting the results of EQCM measurements. In both films, the charge transport is complicated by background conductance that most likely results from bulk residual charge. Both polymers are doped by hydrogen ions and the effects of supporting electrolyte anions are negligible. The results obtained from low-amplitude measurements showed that the charge transport through both polymer films is accompanied by irreversible injection processes at the film interfaces. A capacity dispersion in the low-frequency range, most likely related to the existence of different states of hydrogen ions in the film, was observed for both polyamines. The problems concerning the treatment of the impedance data obtained for slow injection processes are also discussed.
Electropolymerization of p-phenylenediamine (pPD) on Pt-electrode from a deoxygenated aqueous acid medium was carried out using cyclic voltammetry technique. The kinetic parameters were calculated by means of electrochemical data. The experimentally obtained kinetic equation was RP,E ¼ kE [monomer]1.23 [acid] 1.24 [electrolyte]0.94 from the value of the anodic current density. The apparent activation energy (Ea) is found to be 65.1 kJ mol 1. The obtained polymer films have been characterized by X-ray diffraction, elemental analysis, scanning electron microscopy, UV–vis, and IR spectroscopy. The conductivity of the polymer pellets is 6.3 10 7 S cm 1. The mechanism of the electrochemical polymerization reaction has been discussed. TGA is used to confirm the proposed structure and determination of the number of water molecules in the polymeric chain unit.
Journal of the Electrochemical Society, 2013
The electropolymerization of o-Phenylenediamine (oPDA), both in the absence and presence of Fe 3+ in solution, was investigated in detail using cyclic voltammetry concurrently with the quartz crystal microbalance (QCMB) technique. It is shown that a set of redox peaks (A 1 /C 1), seen between 0.05 and 0.4 V is characteristic of the phenazine-like PoPDA polymer, produced by the irreversible radical oxidation of the oPDA monomer at a Au surface and forming an oPDA radical cation that initiates the polymerization step at >0.8 V vs. RHE. The QCMB results showed that ca. 20% of the oxidized product deposits on the Au surface as a redox-active polymer film, with charge compensation by H + injection/expulsion along with some inhalation/exhalation of water. The presence of Fe 3+ in solution during electropolymerization led to very similar electrochemistry, with ca. 50% of the oxidized product forming the redox-active polymer film. The PoPDA films are very smooth and uniform, while films formed in the presence of Fe 3+ are coated with Fe-containing nodules ca. 0.8 μm in diameter, which hinder the further growth of the PoPDA film.
Electrochemical and Spectroelectrochemical Study of m-Phenylenediamine
Chemical Research in Chinese Universities, 2003
Electrochemical and spectroelectrochemical properties of m-phenylenediamine(MPD) were studied by means of cyclic voltammetry and UV-Vis thin-layer spectroelectrochemistry. The cyclic voltammogram of MPD at gold disc electrode has an oxidative peak as well as a reductive peak. But at SnO_(2)∶F film electrode, it has only an oxidative peak, which is an irreversible process. Potential-controlled UV-Vis thin-layer spectra of MPD at SnO_(2)∶F film optically transparent electrode were recorded and a double logarithmic method was applied to treat the spectroelectrochemical data. From the double logarithmic plot, the kinetically modified formal potential E~(0')=0.766 and #alpha#n=0.41 were obtained.
Journal of Applied Polymer Science
Electropolymerization of O-phenylenedi-amine (o-PD) on Pt-electrode from a deoxygenated aqueous acid medium was carried out using cyclic voltammetry technique. The kinetic parameters were calculated by means of electrochemical data. The experimentally obtained kinetic equation was R P , E ¼ k E [monomer] 1.19 [acid] 1.23 [electro-lyte] 0.87 from the value of the anodic current density using cyclic voltammetry technique. The apparent activation energy (E a) is found to be 28.34 kJ mol À1 . The polymer films obtained have been characterized by X-ray diffraction, elemental analysis, scanning electron microscopy, 1 H-NMR, 13 C-NMR, UV-visible, and IR spectroscopy. The mechanism of the electrochemical polymerization reaction has been dis-cussed. TGA is used to confirm the proposed structure and determination of the number of water molecules in the pol-ymeric chain unit. V
Anodic oxidation of p -phenylenediamines in battery grade electrolytes
Electrochimica Acta
The use of anion-inserting organic electrode materials represent an interesting opportunity for developing 'metal-free' rechargeable batteries. Recently, crystallized conjugated diamines have emerged as new host materials able to accommodate anions upon oxidation at potentials higher than 3 V vs. Li + /Li 0 in carbonate-based battery electrolytes. To further investigate the electrochemical behavior of such promising systems, comparison with electroanalytical data of soluble forms of conjugated diamines measured in battery grade electrolytes appeared quite useful. However, the literature on the topic is generally poor since such electrolyte media are not common in molecular electrochemistry. This contribution aims at providing relevant data on the characterization by cyclic voltammetry of unsubstituted, diphenyl-substituted and tetramethyl-substituted p-phenylenediamines. Basically, these three molecules revealed two reversible one-electron reaction upon oxidation corresponding to the electrogenerated radical cation and dication, respectively, combined with the association of electrolyte anions (i.e.,
Poly(o-phenylenediamine) (PoPD) was synthesized from o-phenylenediamine (oPD) using ammonium persulfate (APS) as an oxidizing agent in varying pH of reaction medium. The polymers were characterized by UV-VIS, 1HNMR and FTIR spectroscopy, thermogravimetric and elemental (CHNS) analyses. Solubility tests for the synthesized polymers were performed in various solvents and it was found that the polymer synthesized in lower pH medium was insoluble. The difference in their solubility is due to their structural difference, which can be supported by the proposed mechanisms of polymerizations. The spectral results clearly indicated that the ladder structure was formed in lower pH medium while open ring structure (with some ladder unit) or dimer was formed at higher pH. Fourprobe DC electrical conductivity of the synthesized polymers was also measured. The average DC conductivity of the polymer doped with hydrochloric acid was observed 8.8 x 10-5 S/cm for the synthesized open ring polymer while it was only 1.7 x 10-7 S/cm for the synthesized ladder polymer.
Synthetic Metals, 2008
A method was developed for the determination of the protonation constants (K nH,L HnL ), the stoichiometric factor of the protonation reaction (n) and pH of the half-color transition point (pH 1/2 ) of three different types of electrochemically polymerized poly(aniline) (PANI) and poly(o-methylaniline) (PoMeANI) films. The protonation constants describe the reversible emeraldine base (EB) to emeraldine salt (ES) transition. The calculations of the constants were based on absorbance data obtained from UV-vis measurements of the polymer films equilibrated in pH buffer solutions between pH 2 and 12.
Journal of Electroanalytical Chemistry, 2013
The physico-chemical characteristics of thin poly-(ortho-phenylenediamine) (PPD) films, obtained by electrochemical oxidation of the relevant monomer, are investigated using electrochemical, morphological and spectroscopic techniques. In particular, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) techniques are used to collect information concerning the redox, conductivity and double layer capacitance properties of the PPD film. AFM imaging and Raman spectroscopy results are exploited to characterize the film structure. In this respect, Raman spectra of two possible PPD oligomers are calculated at the B3LYP/6-311G ÃÃ level of the theory.
Electro-oxidation of o-phenylenediamine at platinum electrodes in acetonitrile solutions
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1979
The study of o-phenylenediamine electro-oxidation at platinum electrodes in acetonitrile solutions under different experimental conditions is presented. Cyclic voltammograms show 4 oxidation peaks, which are assigned to o-phenylenediamine, o,o'-diamineazobenzene and protonated o-phenylenediamine anodic oxidation. An additional prepeak system is apparent at potentials less anodic than the first peak in successive scans. This prepeak system evidences the presence of two redox systems diphenylamine and H ÷, derived from the initial oxidation product o-phenylenediamine cation radical. The effect of base and acid addition is also studied, o,o'-Diamineazobenzene was identified as one of the principal soluble products in preparative scale electrolysis and a general mechanism for o-phenylenediamine oxidation is proposed.