Preparation on iron of a polypyrrole (PPy) electrode modified with copper by the electrochemical cementation process

Conducting polypyrrole electrodes obtained under galvanostatic electropolymerization on iron from aqueous solutions of pyrrole and oxalic acid were modified with copper particles using the electrochemical cementation process. The electrochemical response of these modified electrodes was compared to that of the unmodified polymer electrode and also to that of bare metallic copper. The modified polypyrrole electrode showed noticeable enhancement for the rate of proton reduction.     

Humic acid/polypyrrole on a paraffin‐impregnated graphite electrode and its use in arsenic extraction

A novel and simple electrode with rapid preparation was developed with humic acid (HA) and polypyrrole (PPy) films. The method for modified electrode preparation embraced the abrasive transfer technique on a paraffin‐impregnated graphite electrode (PIGE) followed by the electrochemical incorporation of a PPy polymeric film upon bare PIGE and PIGE/HA electrodes. Cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry were used for the study of the modified electrodes. Morphological characterization was performed by scanning electron microscopy. The obtained results demonstrated that the presence of HA did not affect the electrical properties of the system but indeed provoked changes in the polymer morphology, turning it more granular. Next, PIGE/HA/PPy was tested in arsenic solutions [As(V)] because arsenic contamination of water is an important worldwide environmental issue because of the sources of arsenic contamination of water come from both natural processes and anthropogenic activities. The modified electrode displayed good and reversible extraction properties toward the analyte in acid medium and was 18% more efficient than a previously reported PPy‐modified electrode (PIGE/PPy). From an environmental standpoint, this novel application of conductive polymer properties with the chelating capacity of humic substances constitutes a first step in the development of more efficient technologies for the removal of contaminants present in soil–water media. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Electrochemical preparation and characterization of poly(1-amino-9,10-anthraquinone) films

Poly(1-amino-9,10-anthraquinone), PAAQ, films were prepared by electrochemical oxidation of the monomer, AAQ, in acetonitrile using LiClO₄ as supporting electrolyte. The influence of scan repetition, scan rate and monomer concentration on the formation of polymer film was studied. The electrochemical behavior of the formed polymer films was investigated in both non-aqueous and aqueous media. The prepared films were found to be more stable in organic solvents than in aqueous solutions. The investigated organic solvents are methanol, ethanol, acetone, carbon tetrachloride, benzene, and chloroform. The polymer film shows electrochemical response in both non-aqueous and aqueous media. In non-aqueous solutions it has a wide potential range of electroactivity (from −1.5 to +1.3 V). In aqueous media the polymer film shows electrochemical response in the potential range between −0.3 and +1.3 V only. The presence of quinone units suggests potential applications in diverse areas such as electrocatalytic processes and lithium ion batteries.     

Preparation and characterisation of poly(3,4-ethylenedioxythiophene) and poly(3,4-ethylenedioxythiophene)/poly(neutral red) modified carbon film electrodes, and application as sensors for hydrogen peroxide

Poly(3,4-ethylenedioxythiophene) (PEDOT) films have been prepared for the first time on carbon-film electrodes (CFE) in aqueous solution using electropolymerisation by potential cycling, potentiostatically and galavanostatically. Characterisation of the modified electrodes was done by cyclic voltammetry and electrochemical impedance spectroscopy and the stability of the polymer films was probed. The coated electrodes were tested for application as hydrogen peroxide sensors, by oxidation and reduction. A novel polymer film was also formed by modification of CFE by co-electropolymerisation of EDOT and the phenazine dye neutral red (NR) – (PEDOT/PNR) with a view to enhancing the properties for sensor applications. It was found that hydrogen peroxide reduction at the PEDOT/PNR coated electrodes could be carried out at a less negative potential, the sensor performance comparing very favourably with that of other polymer-modified electrodes reported in the literature.     

Synthesis of 10 nanometric copper clusters in a polymer matrix by a solution‐reduction synthesis (SRS)

Nanometric metal clusters in a polymer host were synthesized by a solution‐reduction route in a swelling cathode film (SCF) containing metal ions (such as Cu²⁺). The TEM results show that the scale of the clusters is about 10 nanometers and the distribution of their diameter is very narrow. The X‐ray diffraction and the electron diffraction patterns confirm that the reduced clusters are the crystallites of metal (copper). The scale of nanometric clusters is affected by the electrochemical conditions in the reactions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1857–1864, 2000     

Stability and electrical properties of polyaniline films formed with EDTA and FeEDTA in the electrolyte

The incorporation of EDTA and Fe([scii/iii])EDTA into polyaniline films has been achieved by electropolymerization of aniline in acid solutions at constant potential. The stability and electrical properties of these films have been studied by cyclic voltammetry and electrochemical impedance spectroscopy. The presence of FeEDTA species inhibits the second redox process in the polymer film corresponding to the emeraldine/pernigraniline transition and decreases degradation of these films upon cycling to positive potentials. EDTA increases the degree of cross-linking reactions within the film and leads to less conducting and thinner films compared to those obtained with FeEDTA in the electrolyte.     

Conducting poly(<Emphasis Type="Italic">N</Emphasis>-(1-Naphthyl) ethylene-diamine dihydrochloride) electropolymerization,characterization and electroanalytical applications

Uniform conducting polymer films of poly(N-(1-Naphthyl) ethylene-diamine dihydrochloride), PNED, were prepared conveniently and reproducibly by the anodic oxidation of the monomer, N-(1-Naphthyl) ethylene-diamine dihydrochloride, NED, in an acidic aqueous solution using the conventional potentiodynamic technique. The different parameters influencing the preparation conditions like monomer concentration, solvent constitution, scan range, scan rate, scan repetition, rotation speed of the working electrode and the type of the substrate were investigated and the optimum preparation conditions are specified. The stability of the prepared films was tested in both aqueous and non-aqueous media. The characteristics of the polymer films and their electrochemical activity towards catalyzing some technologically promising redox reactions were also examined. The films were found to be very stable in aqueous solutions and in some organic solvents like acetone, acetonitrile, and chloroform and dimethyl sulfoxide. The film stability was found to depend on the solution pH. The polymer films were capable of catalyzing the redox processes of several natural products and amino acids e.g. vitamin C and glycine. The polymer film possesses electrochromic properties and the color of the film changes from purple to violet to dark blue and then to brown according to the preparation and/or polarization conditions. The electrochromic properties are related to polaron formation, which subsequently oxidizes to diimine species followed by the oxidation of the aromatic ring. The mechanism of the polymerization process was investigated and discussed. The process involves deprotonation reactions and a head-to-tail coupling of the oxidized monomer with cation radicals. An erratum to this article can be found at     

Electrocatalytic oxidation of chlorophenols by electropolymerised nickel(II) tetrakis benzylmercapto and dodecylmercapto metallophthalocyanines complexes on gold electrodes

This work reports on the use of nickel(II) tetrakis benzylmercapto (NiTBMPc) and dodecylmercapto (NiTDMPc) metallophthalocyanine complexes films on gold electrodes for the electrochemical oxidation of 4-chlorophenol (4-CP) and 2,4,5-trichlorophenol (TCP). Both NiTBMPc and NiTDMPc complexes were successfully deposited on gold electrodes by electropolymerisation. The films were electro-transformed in aqueous 0.1 M NaOH solution to the ‘O-Ni-O oxo’ bridged form. For both complexes, films with different thickness were prepared and characterised by electrochemical impedance and UV-vis (on indium tin oxide) spectroscopies and the results showed typical behaviour for modified electrodes with increasing charge transfer resistance values (R_p) with polymer thickness. The poly-Ni(OH)NiPcs showed better catalytic activity than their poly-NiPcs counterparts.     

Electrochemical synthesis and anticorrosive properties of Nafion-poly(aniline-co-o-aminophenol) coatings on stainless steel

The objective of this work was to compare the electrochemical behavior and possible anticorrosive properties of composite with Nafion^®, poly(aniline-co-o-aminophenol) (P(An-co-OAP)) and polyaniline (PAn) films with those of corresponding simple films. The electrochemical synthesis of polymer films was carried out on stainless steel AISI 304 (SS) surfaces by using the cyclic potential sweep (CPS) deposition. Scanning electron microscopy (SEM) was used for the characterization of the structure and morphology of deposited films. Evaluation of anticorrosive properties of films in 0.5 M H₂SO₄ without and with chlorides was achieved by monitoring the open circuit potential (E_OC) of coated SS electrodes as well as by tracing the anodic current-potential polarization curves. These studies have shown that the SS remains in its passive state in the presence of polymer coatings. Composite with Nafion^®, P(An-co-OAP) and PAn films, keep their redox activity in chloride-containing acid solutions providing almost a complete protection of the SS substrate against pitting corrosion. These films prevent chloride exchange with solution because of the cation permselectivity of the Nafion^® membrane. The charge compensation during redox reactions occurs mainly by protons since sulfonate groups of Nafion^® act as dopants in composite films. The redox behavior of the Nafion^®-P(An-co-OAP) film is improved as compared with that of the Nafion^®-PAn film in both Cl⁻-free and Cl⁻-containing solutions. This behavior may be ascribed to the functional group -OH that facilitates charge compensation through proton during redox reactions.     

Electrochemical behaviour of metal hexacyanoferrate converted to metal hydroxide films immobilized on indium tin oxide electrodes—Catalytic ability towards alcohol oxidation in alkaline medium

In this work, we demonstrate a simple method to modify indium tin oxide (ITO) electrodes in order to perform electro-catalytic oxidation of alcohols in alkaline medium. Metal hexacyanoferrate (MHCF) films such as nickel hexacyanoferrate (NiHCF) and copper hexacyanoferrate (CuHCF) were successfully immobilized on ITO electrodes using an electrochemical method. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the structural and morphological aspects of MHCF films. Cyclic voltammetry (CV) was used to study the redox properties and to determine the surface coverage of these films on ITO electrodes. Electrochemical potential cycling was carried out in alkaline medium in order to alter the chemical structure of these films and convert to their corresponding metal hydroxide films. SEM and XPS were performed to analyze the structure and morphology of metal hydroxide modified electrodes. Electro-catalytic oxidation ability of these films towards methanol and ethanol in alkaline medium was investigated using CV. From these studies we found that metal hydroxide modified electrodes show a better catalytic performance and good stability for methanol oxidation along with the alleviation of CO poisoning effect. We have obtained an anodic oxidation current density of ∼82 mA cm⁻² for methanol oxidation, which is at least 10 fold higher than that of any metal hydroxide modified electrodes reported till date. The onset potential for methanol oxidation is lowered by ∼200 mV compared to other chemically modified electrodes reported. A plausible mechanism was proposed for the alcohol oxidation based on the redox properties of these modified electrodes. The methodology adapted in this work does not contain costlier noble metals like platinum and ruthenium and is economically viable.     

Voltammetric behavior study of folic acid at phosphomolybdic-polypyrrole film modified electrode

The electrochemical behavior of folic acid at the Keggin-type phosphomolybdate (PMo₁₂) doped polypyrrole (PPy) film modified glassy carbon electrode (PMo₁₂-PPy/GCE) was studied. PMo₁₂ doped PPy modified electrodes were achieved during the electrochemical preparation of the polymer films in aqueous solution. The redox behavior of the modified electrode was described by cyclic voltammetry. The electrochemical behavior of folic acid at PMo₁₂-PPy/GCE was studied by 0.5 order differential voltammetry. Numerous factors affecting the reduction peak currents of folic acid at PMo₁₂-PPy/GCE were optimized to maximize the sensitivity. The results showed that folic acid had high inhibitory activity toward the reduction of modified electrode in 0.01 M H₂SO₄. The reduction peak currents were directly proportional to the concentration of folic acid from 1.0 × 10⁻⁸ to 1 × 10⁻⁷ M with correlation coefficient of 0.9976, a detection limit of 1.0 × 10⁻¹⁰ M of folic acid was estimated. From the inhibitory effect of folic acid on PMo₁₂-PPy/GCE, the apparent formation constant of folic acid with the modified film was estimated. This modified electrode showed excellent sensitivity and stability for the determination of folic acid. The response mechanism of folic acid at PMo₁₂-PPy/GCE was discussed in detail.     

Electrochemical behavior of Au nanoparticle deposited on as-grown and O-terminated diamond electrodes for oxygen reduction in alkaline solution

Au nanoparticle was electrochemically deposited on both as grown and oxygen-terminated (O-terminated) boron-doped diamond (BDD) films. The surface coverages of Au nanoparticle were 0.07 and 0.18 corresponding to the areas of Au 0.012 and 0.029 cm², respectively, as noted from linear sweep voltammetry. The SEM studies indicated different morphologies of Au deposition such as random distribution of small spherical particles at both the grain boundaries and the facets on the as grown diamond film and clusters principally on the cross edges of two facets on the O-terminated diamond. The electrochemical behavior for oxygen reduction was examined using differential pulse voltammetry (DPV), which confirmed the higher catalytic efficiencies of Au deposited as grown and O-terminated BDD electrodes when compared to a polycrystalline Au electrode. Moreover, the mechanism of Au nanoparticle deposited BDD films for the oxygen reduction was investigated by ac impedance and hydrodynamic voltammetric methods.     

载铂聚苯胺/聚砜复合膜修饰电极对甲醇的电催化氧化行为研究

采用循环伏安法制备聚苯胺(PAN)/聚砜(PSF)复合膜修饰电极,在其上电沉积铂粒子,制得载铂聚苯胺/聚砜复合膜修饰电极,用循环伏安法和交流阻抗法研究它对甲醇的电催化氧化行为。复合膜的化学组分用FTIR进行表征,复合膜内层载铂后的表面形态用SEM进行表征。结果表明,复合膜的内层(与工作电极接触的一面)是聚苯胺,外层(与溶液接触的一面)是聚砜,铂粒子在复合膜内层的多孔聚苯胺上均匀沉积,从而使载铂聚苯胺/聚砜复合膜修饰电极对甲醇有好的电催化氧化性能。     

Electrochemical properties of benzylmercapto and dodecylmercapto tetra substituted nickel phthalocyanine complexes: Electrocatalytic oxidation of nitrite

Nickel tetrakis(benzylmercapto)phthalocyanine (NiTBMPc) and nickel tetrakis(dodecylmercapto)phthalocyanine (NiTDMPc) complexes were synthesized and their spectral and electrochemical properties reported. The CV showed four or five redox processes for NiTBMPc and NiTDMPc, respectively. For the first time, spectroelectrochemistry gave evidence for the formation of Ni^II/Ni^I process in a NiPc complex. The rest of the processes were ring based. The NiTBMPc complex was successfully deposited on both gold and glassy carbon electrodes by electropolymerisation while NiTDMPc complex was deposited on gold electrode only. The films were electro-transformed in aqueous 0.1 M NaOH solution to the O–Ni–O oxo bridged form. The modified electrodes were characterized using electrochemical impedance spectroscopy and the results showed typical behavior for modified electrodes. Electrodes with poly-Ni(OH)Pcs films exhibited higher charge transfer resistance values, R_p than their corresponding poly-NiPcs films counterparts. All the modified electrodes showed improved catalytic activities than the unmodified electrodes towards nitrite ions electrooxidation. Better catalytic activities were observed for the modified electrodes when they were transformed to O–Ni–O oxo bridge form. All the modified electrodes exhibited high resistance to electrode surface passivation.     

Characterization of the barrier layer of nanoporous alumina films prepared using two different contact configurations

We investigated the structure of the barrier layers of nanoporous alumina formed by anodization of aluminum films laid over platinum electrodes by cyclic voltammetry technique and scanning electron microscopy. Two methods of anodization were employed in this study—the conventional sub-surface anodization method and a novel pipette anodization method. Measurements of the electron transfer rate constant values at these alumina-modified electrodes demonstrated very different alumina microstructures at the barrier layer region for these two types of alumina-modified electrodes. The sub-surface anodized electrode consists of a barrier layer, which forms a kinetic barrier for the electrochemical reaction of a redox probe at the underlying platinum electrode. In contrast, the quasi-reversible electrochemical behaviour of a redox probe at the pipette-anodized electrodes closely resembles the reaction observed at a bare platinum electrode. Scanning electron microscopy revealed pore structures along the underside surface of the alumina overlayer of a pipette-anodized electrode. These results indicate alumina modified eletrodes fabricated using the pipette anodization method comprise channels which penetrate the barrier layer, giving rise to ‘barrier layer-free’ alumina films.     

Electrodes covered with thin,permeable polymer films

Because of the recent interest in electrodes modified with thin polymer films the question of permeability of such films to electrolytes and electroactive species is discussed. Glow-discharge polymer films prepared on platinum electrodes from 4-vinylpyridine were used as model systems. They were investigated mainly with electrochemical techniques. ln particular, the analysis of the electrode impedance over a frequency range of 10–3000 Hz gave valuable information about the structure of the metal—polymer interface in presence of the electrolyte.The films prepared on the anode of the glow discharge were found to act as semi-permeable membranes. Hydrogen could be oxidized on the platinum—polymer interface of these polymer covered electrodes at rates comparable to uncovered platinum, while the films were impermeable to iron ions. The matrix prepared on the cathode was more rigid due to cross-links, and thus less permeable.The polymer matrix was more or less electroactive itself. This was probably due to quinone-type groups formed with oxygen and water after the glow-discharge polymerization process. The oxidation and reduction of these groups gave rise to a Warburg-type contribution to the electrode impedance.     

Optimization of the electropolymerization of 1-amino-9,10-anthraquinone conducting films from aqueous media

The optimum conditions for the electrochemical preparation of poly(1-amino-9,10-anthraquinone), PAAQ, films in environmentally safe aqueous solutions were investigated. The conducting polymer films were prepared by electrochemical oxidation of 1-amino-9,10-anthraquinone, AAQ, in sulfuric acid solutions in the potential range from 0.0 to +1.3 V. The influence of scan repetition, scan rate, and monomer concentration on the formation process and the properties of the polymer film were studied. The electrochemical response of the formed polymer film was investigated in both aqueous and non-aqueous media. The polymer films were found to be stable in aqueous acidic media. In non-aqueous solutions, like acetonitrile, dimethyl sulfoxide and dioxin, the polymer films showed remarkable degradation. The best electrochemical response of the PAAQ films was found to be in the potential range between +0.3 and +0.9 V. The presence of quinone units in the polymer film chain suggests promising applications of these conducting polymers in lightweight (rechargeable) batteries, electrochromic display devices, and biosensor and corrosion protection.     

Electrochemical and oxygen reduction behaviour of solid silver-bismuth/antimony electrodes in KOH solutions

Oxygen reduction behaviour at silver-low bismuth/antimony electrodes was investigated by electrochemical methods in KOH solutions. The electrochemical redox characteristics such as peak multiplicity, peak currents and peak potentials on these electrodes under both potentiostatic steady state and cyclic voltammetric conditions were obtained. The anomalies associated with the redox peak potential values both in the anodic and cathodic branches of the cyclic voltammograms were attributed to the distinct electrochemical behaviour of bismuth/antimony on the electrode surface along with silver. The behaviour of these electrodes for the electrocatalytic cathodic reduction of oxygen was also investigated both by potentiostatic steady state and cyclic voltammetric techniques under rotating conditions. The kinetic parameters corresponding to the electrochemical reduction of oxygen on these electrodes were obtained. These electrodes were ranked with respect to their electrocatalytic activity both for the oxygen reduction and evolution reactions.     

Influence of chromium content on microstructural and electrochemical supercapacitive properties of vanadium nitride thin films developed by reactive magnetron co-sputtering process

Two-dimensional nanostructured transition metal nitride-based thin film electrodes have been gaining importance in the electrochemical supercapacitor applications. In this work, Cr doped vanadium nitride (VN) thin films as an electrode material for high-performance supercapacitors have been demonstrated. In this study, reactive magnetron co-sputtering technique was adopted to fabricate phase pure VN as well as VN films doped with different Cr contents. These films were directly investigated as electrodes without using any additional binders. The phase purity and the surface chemistry of the Cr doped VN thin films were investigated using XRD and XPS techniques. Furthermore, EDS and X-ray elemental mappings were used to confirm the content of Cr and its distribution in these electrode films. The Cr −5.7 at. % doped VN thin film electrodes exhibited an extraordinary supercapacitor performance with the maximum areal capacitance of 190 mF/cm² compared to the areal capacitance of 27 mF/cm² for the un-doped VN at a scan rate of 10 mV/s. Moreover, the Cr-5.7 at. % doped VN thin film electrodes showed excellent electrochemical cycling stability and excellent reversibility with the capacitance retention of 92.4 %. It could be noticed that the incorporation of metal such as Cr could be a viable method to improve the electronic or ionic conductivity of the metal nitrides for supercapacitor applications.     

Etude de la polymerisation electrochimique de triphenylamines substituees par le groupe hydroxy-1 ethyle. Preparation d'electrodes modifiees par des films de polymeres redox

Upon anodic oxidation of 4-(1-hydroxyethyl) triphenylamine 1 and 4,4′-di(1-hydroxyethyl)tri-phenylamine 2, a redox polymer grows on the electrode, and another one precipitates in the solution. The mechanism of polymerization of these carbinols is discussed on the basis of electrochemical, infrared and mass studies. The polymerization, initiated by oxidation, proceeds by acid catalysis. The redox polymer contains benzidine and triphenylamine moieties.Study of electrodes modified by electropolymerization of 1 shows that the rate of film electrochemical reactions is controlled by the rate of diffusion of the electrochemical charge through the film.