Electrochemical synthesis of polymer based on 4-(2-furyl) benzenamine: Electrochemical properties,characterization and applications

4-(2-Furyl) benzenamine (FBA), was successfully synthesized by a simple method including substitution of furan on p-nitroaniline followed by reduction of nitro group. Structure of the synthesized monomer was verified using IR, ¹H NMR and GC–MS techniques. Corresponding poly(4-(2-furyl) benzenamine) (PFBA) was electrochemically synthesized in acidic aqueous and organic solutions by cyclic potential sweep method. Characterization of the resulting polymer was performed by cyclic voltammetry (CV), IR, UV–vis spectroscopy, and scanning electron microscopy (SEM). Effect of solvent on the electroactivity of the polymer modified electrode was investigated. The HOMO, LUMO levels and band gap energies of the doped and undoped form of the PFBA were calculated using UV–vis and CV data. The electrochromic properties and corrosion behavior of PFBA were studied. The electrochromic properties of the copolymer film, electrochemically coated on transparent conductive oxide, corroborate multi-color electrochromic behavior of the polymer whenever the applied potential was switched from reducing (yellow) to oxidizing status (green). The FBA polymer was found to exhibit enhanced corrosion protection effect on steel electrode in comparison with corresponding polyaniline (PANI) and polyfuran (PFu) homopolymers based on series of electrochemical measurements in 3.5 wt% NaCl electrolyte solutions.     

Electrochromic behavior and stability of polyaniline composite films combined with prussian blue

The electrochromic behavior of polyaniline–poly(vinyl alcohol) composite films (CPAn–PVA) combined with electrochemically synthesized Prussian blue films (PB) was investigated in LiClO₄? CH₃CN nonaqueous aprotic solution. The combination was achieved by chemical deposition of CPAn–PVA on PB. When the combined films (CPAn–PVA–PB) are prepared with the appropriately low quantity of PB, CPAn–PVA–PB showed various visible absorption spectra overlapped roughly with the absorption of the component materials at different applied potentials. CPAn–PVA–PB provided the color change from green to blue at much lower applied potential than did CPAn–PVA. However, the combined PB eliminates protons from the first oxidized polyaniline chains to decrease the electrochemical activity of polyaniline. Therefore, to construct multicolor electrochromic devices by the combination of polyaniline with the other electrochromic materials, it is necessary to select the materials containing no deprotonation activity. © 1994 John Wiley & Sons, Inc.     

Poly(3‐chlorothiophene) films prepared by the direct electrochemical oxidation of 3‐chlorothiophene in mixed electrolytes of boron trifluoride diethyl etherate and sulfuric acid

3‐Chlorothiophene (CT) was electrochemically polymerized in mixed electrolytes of a boron trifluoride diethyl etherate solution containing 0–20% (by volume) sulfuric acid. The oxidation potentials of the monomer in these media were measured to be only 1.06–1.31 V (vs Ag/AgCl). These values were much lower than that of CT in acetonitrile and 0.1 mol/L (Bu)₄NBF₄ (1.92 V vs Ag/AgCl). Poly(3‐chlorothiophene) (PCT) films with conductivities of 0.1–2 S cm^?1 were obtained. The structure, morphology, and electrochemical behavior of the PCT films also were investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 502–509, 2003     

Electrochemical and chemical investigations of the co-polymers of 3-aminobenzenesulfonic acid with aromatic amines for their application in electrochromic devices

The chemical oxidative polymerization and electrochemical polymerization of 3-aminobenzenesulfonic acid with aromatic amines have been carried out in p-toluenesulfonic acid which acts as a supporting electrolyte as well as an external dopant. The presence of –SO₃H groups in the ABSA co-monomer allows the copolymer to acquire intrinsic protonic doping ability. The electrochemically synthesized polymers and copolymers have been characterized by cyclic voltammetry for analyzing the growth of copolymers and chronoamperometry studies for their applications to the electrochromic devices. In addition to construction of electrochromic devices (ECDs), the electrochromic properties of the polymer films were further investigated. Electrochromic switching stability of the devices was estimated from switching times between their oxidized and reduced states, which indicates that the homopolymers and copolymer can be used for promising electrochromic devices. Chemically synthesized copolymers were also characterized using various techniques like Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy and electrical conductivity at room temperature.     

Synthesis,characterization, and redox and electrochromic behaviors of poly(3-n-octyloxythiophene)

Poly(3-n-octyloxythiophene), a conjugated polymer, which possessed solubility in common organic solvents, was synthesized by electrochemical polymerization in the presence of lithium perchlorate as the supporting electrolyte and sodium dodecyl sulfate as the surfactant in an aqueous medium. Characterizations of the intermediate, monomer, and polymer were performed by NMR spectroscopy, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, and gel permeation chromatography. The process of electrochemical polymerization and the electrochemical redox behaviors were investigated by cyclic voltammetry and the potentiostatic method. A poly(3-n-octyloxythiophene) film that was deposited on a platinum electrode was found to exhibit electrochromic behaviors, and it switched electrochemically between blue–green oxidized and dark red reduced states. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Detection and determination of CrVI in solution using polyaniline modified quartz crystal electrode

Conducting polymers such as polyaniline and polypyrrole exhibit novel sensoric properties and are able to interact chemically or electrochemically with the species of interest for detection. In the current investigation, construction of a sensor based on an electrochemical reaction between Cr^VI and a thin layer of polyaniline, coated at the surface of quartz crystal electrode, is reported. Polyaniline was synthesized, electrochemically, at the surface of quartz crystal electrode. It was then reduced at ?0.1 V versus Ag/AgCl. The modified electrode was exposed to various concentrations of Cr^VI solutions ranging from 10^?7 to 10^?1M. Mass changes of the polymer‐modified electrode due to the reaction between Cr^VI and polyaniline was found to be linear, corresponding to the concentration of Cr^VI. The experiments in both acidic and nonacidic conditions were performed. In both conditions, linear double‐loga thmic calibration curves of mass change of the polymer film versus Cr^VI concentration were obtained. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2772–2780, 2002     

Electrochromism of nickel oxide thin film with polymer gel electrolyte

Polymer gel electrolytes were investigated for an electrochromic device (ECD) using nickel oxide thin film. Poly(ethylene oxide) (PEO) derivatives were cross‐linked and swelled in KOH–aqueous solution giving a hydrogel electrolyte. The ECD containing the uniformly cross‐linked hydrogel showed good result in electrochromic switching performance. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1305–1308, 2002     

Promotional effects on a PtRu/C catalyst-electrode interfaced with aqueous electrolytes: electrochemical metal support interaction (EMSI) and electrochemical promotion of catalysis (EPOC)

The kinetics of the catalytic oxidation of H₂ on PtRu/C gas diffusion electrode (GDE) was studied by interfacing the electrode with aqueous electrolytes at different pH values. The conducting electrolytes were aqueous solutions of varying concentrations of KOH and HClO₄ so that the pH was ranging between 2 and 13. The open circuit catalytic reaction rates exhibit the lowest value at pH = 13, while the catalytic activity is progressively increasing with decreasing pH values. The enhancement of the open circuit catalytic reaction rate can be even an order of magnitude higher in the acidic solution with respect to the alkaline electrolyte. It is shown that the nature of the aqueous electrolyte plays the role of an active catalyst support for the PtRu/C electrode, which drastically affects its catalytic properties. This is substantiated through the electrochemical equilibrium charge transfer reactions at the catalyst-electrode/electrolyte interface:

Au dissolution during the anodic response of short-chain alkylthiols with polycrystalline Au electrodes

The electrochemical characteristics of polycrystalline Au in LiClO₄ electrolyte solutions containing 3-mercaptopropionic acid (MPA) or meso-2,3-dimercaptosuccinic acid (DMSA) were studied with linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) over a wide range of positive potentials vs. Ag/AgCl. The EIS data exhibited linear capacitive behaviour at 0.0 V with either MPA or DMSA added directly to the electrolyte suggesting the formation of an adsorbed layer of the alkylthiol on the electrode surface. Above this potential, a single well-defined impedance loop appeared for electrolyte solutions containing DMSA or MPA, an observation indicative of a charge transfer reaction that could be related to several processes including oxidative desorption, oxidation of the alkylthiol, or Au oxidation/dissolution. To test for Au dissolution, the electrode was held at 0.8 V vs. Ag/AgCl for 12 h in electrolytes containing MPA or DMSA followed by surface analysis with Atomic Force Microscopy and solution analysis with Atomic Absorption Spectroscopy. When the electrolyte contained MPA, the extended potential holding procedure resulted in significant roughening of the electrode with no detectable quantities of Au in the electrolyte. X-ray photoelectron spectroscopy (XPS) analysis of the Au surface revealed an additional species in the Au 4f_7/2 spectrum indicating the presence of an insoluble electrochemically generated Au(I)–MPA species. When the electrolyte contained DMSA, the Au electrode appeared smoother, 56.6 ± 9.6 ppb of Au was detected in the electrolyte and the XPS analysis displayed a single species in the Au 4f_7/2 spectrum indicative of metallic Au after the potential holding procedure. Both observations with MPA and DMSA support the charge transfer resistance to be at least partially related to the corrosion of Au, but also suggest that an electrochemically generated Au–DMSA species is soluble and of potential industrial relevance.     

Electrochemical supercapacitor material based on manganese oxide: preparation and characterization

A novel class of electrochemical supercapacitor electrode material has been electrochemically synthesized from a manganese halide complex in water-containing acetonitrile electrolyte at room temperature. This material has been physically and chemically characterized by scanning electron microscopy, X-ray photoelectron microscopy (XPS), FT-Raman microscopy and cyclic voltammetry. XPS and FT-Raman characterization suggest that this material is composed of manganese oxide with a chemical composition of Mn₃O₄ and containing a moderate amount of carbon. Cyclic voltammetric characterization indicates that this material has higher electronic conductivity than usually seen for manganese oxide and that it shows fast kinetics for the charge-discharge process in both aqueous and acetonitrile electrolytes. The material provides a large pseudocapacitance over a potential window of about 1 V in aqueous electrolyte and about 2 V in acetonitrile electrolyte. It is therefore a good candidate as a material for an electrochemical supercapacitor electrode.     

Synthesis of polyaniline/polytoluidine block copolymer via the pernigraniline oxidation state

Polyaniline was electrochemically synthesized in the emeraldine oxidation state and then converted to the pernigraniline oxidation state by applying an electric potential under optimized conditions. The stability/reactivity of polyaniline in the pernigraniline oxidation state was evaluated in various aqueous media. The products of the reduction of the pernigraniline oxidation state by o-toluidine were analyzed by gel permeation chromatography, ultraviolet–visible and infrared spectroscopies, and cyclic voltammetry. The results are consistent with the synthesis of a diblock copolymer of polyaniline/poly(o-toluidine) and also of some poly(o-toluidine) homopolymer in the emeraldine oxidation state as a side product.     

Electrochemical Behavior of Polyaniline,Poly(o-Anisidine) and Their Copolymer Thin Films in Inorganic and Organic Supporting Electrolytes

Abstract

The influence of inorganic and organic supporting electrolytes on electrochemical, optical, and conducting properties of polyaniline, poly(o-anisidine), and poly(aniline-co-o-anisidine) thin films were investigated. Homo- and copolymer thin films were synthesized electrochemically, under cyclic voltammetric conditions in aqueous solutions of inorganic acids, viz., H₂SO₄, HCl, HNO₃, H₃PO₄, and HClO₄ and organic acids, viz., benzoic acid, cinnamic acid, oxalic acid, malonic acid, succinic acid, and adipic acid, at room temperature. The films were characterized by cyclic voltammetry, ultraviolet (UV)–Visible spectroscopy, and conductivity measurements using four probe technique. The optical absorption spectra indicated that the formation of the conducting emeraldine salt (ES) phase took place in all the inorganic supporting electrolytes used whereas, inorganic supporting electrolytes ES phase formed only with oxalic acid. It was also observed that the current density and conductivity of thin films are greatly affected by the nature and size of the anion present in the electrolyte. The formation of copolymer has also been confirmed by differential scanning calorimetry.     

Current‐voltage characteristics of conducting polypyrrole in solid polyethylene oxide electrolytes

Current‐voltage characteristics were studied for polypyrrole films contacted with different electrolytes in aqueous form and complex polymer solid electrolytes. Cyclic voltammograms for the conducting polymer in aqueous medium exhibited the typical oxidation and reduction peaks, whereas for solid polymer electrolytes, there was large asymmetry in curves; with the anodic current being much higher than that in the cathodic region. A rapid switching‐type response was noted in the case of polyethylene oxide‐cupric chloride complex as solid electrolyte. This effect was pronounced when the same complex contained the polypyrrole deposited within it as a composite. These various results have been discussed in the light of different energy levels in the conducting polymer and the contacting medium, as well as the formation of a microdispersed system with higher charge transport. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2059–2067, 1999     

Synthesis and properties of oxalic acid-doped polyaniline

Conductive polyaniline was synthesized in aqueous 1.0M oxalic acid containing 0.1 M aniline by electrochemical and chemical oxidation and characterized by conductivity, solubility, ultraviolet and infrared spectroscopy, and cyclic voltammetry. The solubility experiments showed that the solubility of oxalic acid-doped polyaniline in dimethylsulfoxide and dimethylformaide increased to a certain extent. The soluble part of the polyaniline was free from impurities such as quinones. Cyclic voltammetric studies in oxalic acid medium revealed that aniline exhibited a similar behaviour to that in H₂SO₄ and the polymerization rate was much slower than that in H₂SO₄.     

Electrocatalytic oxidation of methanol and C1 molecules on highly dispersed electrodes Part II: Platinum-ruthenium in polyaniline

The oxidation of methanol and C1 molecules at electrodes modified with polyaniline and particles of platinum and ruthenium has been studied in aqueous HClO₄ electrolyte. The platinum and ruthenium particles were incorporated into the polyaniline film by electrochemical reduction. The activity for the oxidation of C1 molecules is higher for bimetallic electrodes than for polyaniline-coated electrodes modified with platinum alone. Indeed, a negative shift of more than 100 mV is observed as compared to the potential obtained with a polyaniline film modified by pure platinum. Moreover, the oxidation of methanol is faster and more complete on the Pt-Ru modified polyaniline electrode, since carbon dioxide is the main reaction product.     

Voltammetric and spectroelectrochemical studies on 4-aminophenol at gold electrodes in aqueous and organic media

Voltammetric and UV-Vis spectroelectrochemical studies on 4-aminophenol (4-AP) at gold electrodes have been carried out in conventional electrochemical and in novel spectroelectrochemical cells. As base electrolytes acetonitrile with 10⁻² M tetrabutylammonium hexafluorophosphate as supporting electrolyte and acetate buffer (pH 4.6) solutions have been used. 4-AP was electrochemically oxidized at gold electrodes at potentials >+0.1 V in aqueous solutions and at potentials >+0.5 V in acetonitrile solutions. The formation of an oxidation product has been characterized in situ by UV-Vis spectroscopy in a novel optical thin-layer spectroelectrochemical cell.     

Electrosynthesis and characterization of a conductive polythiophene deriving from a terthiophene monomer

The electrochemical polymerization of the 3,3″-di[(S)-(+)-2-methylbutyl]-2,2′:5′,2″-terthiophene (DMBTT) monomer was carried out potentiodynamically on indium tin oxide (ITO), Pt or glassy carbon (GC) electrodes in anhydrous CH₃CN with TBAPF₆ as supporting electrolyte. Films with good adhesion were obtained for all the tested substrates and they were characterized by various analytical techniques including UV–Vis–NIR absorption spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM), and gel permeation chromatography (GPC). The most outstanding properties of the electrochemically synthesized polymer were compared with those of the same polymer obtained by a chemical method. The film obtained on ITO displayed a reversible electrochromic behavior under potential switching between −0.50 and +1.00 V vs. SCE.     

Polyaniline electrochromic devices with transparent graphene electrodes

Transparent, conductive and uniform graphene films have been prepared and used as electrodes of the electrochromic devices of polyaniline. Polyaniline films on both graphene and the widely used indium tin oxide (ITO) electrodes showed similar electrochemical and spectroelectrochemical properties. However, graphene electrodes exhibited much higher electrochemical stability than ITO in aqueous acidic electrolytes. The performances of the electrochromic devices with graphene electrodes exhibited slight decrease upon voltage switching while those of the devices with ITO electrodes decreased dramatically. After 300 cycles, the electrochromic devices with graphene electrodes showed much larger optical contrast and shorter switching time than those of the devices with ITO electrodes.     

Enhanced activity of carbon-supported PdCo electrocatalysts toward electrooxidation of ethanol in alkaline electrolytes

Carbon-supported Pd and PdCo (1: 2, 1: 1, 2: 1 and 3: 1) catalysts were synthesized by chemical reduction with NaBH₄. Their electrochemical properties were investigated by cyclic voltammetry, chronoamperometry and CO stripping voltammetry in alkaline electrolytes, and compared with commercial Pt/C and PtRu(1: 1)/C catalysts. In electrochemical oxidation of ethanol in an alkaline electrolyte, marked improvements in the current density and onset potential were observed by incorporating Co into Pd/C to form PdCo/C alloy electrocatalysts. The best catalyst PdCo (1: 1)/C showed performance superior to the commercial Pt/C or PtRu/C catalysts. It is shown that the incorporated Co facilitates the oxidation of strongly-adsorbed carbonaceous intermediate species on the surface of Pd by forming OH^? group and reacts away the intermediates from Pd surface. Thus, PdCo(1: 1)/C catalyst is a promising anode catalyst for direct ethanol fuel cells with alkaline electrolytes.     

Examination of the double-layer capacitance of an high specific-area C-cloth electrode as titrated from acidic to alkaline pHs

The titration of the interfacial capacitance of a C-cloth electrochemical capacitor electrode was undertaken for the purpose of evaluating the cyclic voltammetry (CV) responses as a function of the pH of an aqueous electrolyte over the range of 0–14. As the pH was increased from 0 (aqueous H₂SO₄) to a progressively more alkaline (NaOH) solution of pH 11, a 30% loss in capacitance is seen, partly attributable to the disappearance of the pseudocapacitive peaks based on the oxidation/reduction of the surface quinone groups. As the pH is increased above 11, the capacitance increases ca. 20%, as other surface functionalities (a pyrone derivative and another unknown species) become activated in alkaline solution. When the C-cloth is titrated from pHs of 14 to 2, the CV current profile shrinks (with a concomitant decrease in charge-storage capacity). However, at electrolyte pHs below ca. 2, the quinone functionalities are activated and the charge-storage capacity increases ca. 30% above the initial value. It was found that the CV current responses in pH 14 electrolytes are smaller when the titration is base-initiated, rather than acid-initiated, due to an activation step required to make the pyrone functionalities active in alkaline solution.