Pseudo Capacitive Studies of Polyaniline-Carbon Nanotube Composites as Electrode Material for Supercapacitor

This study describes the formation of composites of polyaniline (PANI)-Carbon Nanotube (CNT) using in situ chemical oxidative polymerization of the monomer aniline. The PANI-CNT composites were characterized by FTIR and UV-Visible spectroscopy and XRD method. The surface morphology of the composites was characterized by scanning electron microscopy (SEM). Pseudo-capacitive behavior of deposited PANI over the surface of CNT was investigated by means of cyclic voltammetry. The composite was mixed with activated carbon for making the electrode. The specific capacitance of the prepared electrode was tested by means of a half cell test. The PANI-CNT composite with 0.02 M aniline in initial polymerization solution had the thinnest layer and highest specific capacitance of 597.82 F/g in 1 M H₂SO_4.     

Effect of cations on polyaniline morphology

Nanostructured polyanilines of different morphologies were prepared by chemical polymerization of aniline with ammonium peroxodisulfate in aqueous HCl using various inorganic and organic chlorides as additives with the aim to determine the effect of cations of the added electrolyte on the morphology, spectroscopic characteristics, and conductivity of formed polyanilines. Chlorides of basic metals: NaCl and CaCl₂ did not show any significant effect while AlCl₃ and organic electrolytes were found to influence the morphology of polyanilines. The effect of organic-electrolyte additives, which actually are ionic liquids, is explained by the organization of their molecules to micellar structures that act as soft templates for emerging polyaniline nanoparticles. The effect of AlCl₃ is ascribed to the transformation of its molecules to [AlCl₄]^? anions.     

Preparation of polyaniline conductive composites with diene‐rubber or polyphenylacetylene

We describe the preparation of polyaniline (PANI‐EB) by aniline oxidation with KIO₃ and the purification of the resulting dedoped polymer by an acetone extraction step to eliminate undesired by‐products from polyaniline, which could generate some safety concerns in the application and use of PANI. Excellent homogeneous and electrically conducting composite films can be prepared from chloroform solutions of purified PANI doped with camphorsulfonic acid in presence of cis‐1,4‐polybutadiene as the film‐forming agent. These films have been characterized by FT‐IR and UV‐VIS‐NIR spectroscopy. A method to synthesisze PANI directly doped with dodecylbenzenesulfonic acid (DBSA) is also reported. DBSA‐doped‐PANI was then used to prepare composites with polyphenylacetylene (PPA) by growing homogeneous films from chloroform solution. These films were conductive and were studied by FT‐IR and UV‐VIS‐NIR spectroscopy. In view of the application of these composites as gas sensors or in “electronic noses”, a short discussion is presented about the criteria used in the selection of the chemical nature of the host polymer where doped PANI is included to confer electrical conductivity. The interaction between the molecules to be detected and the polymeric sensing surface is discussed in terms of physisorption, chemisorption and charge‐transfer‐complex formation. Copyright © 2001 John Wiley & Sons, Ltd.     

Bimetallic Co–Cu polyaniline composites: Structure and electrocatalytic activity

Bimetallic Co–Cu polyaniline composites were produced by oxidative polymerization of aniline, with ammonium peroxydisulfate and hydrogen peroxide as oxidizing agents. Co(II) and Cu(II) chlorides were introduced into the polymer by the in situ method. It was found that the phase constitution of the composites is affected by their synthesis conditions and content of both metals in them. The electrocatalytic activity of the composites in the electrohydrogenation of p-nitroaniline in an aqueous-alcoholic-alkaline medium of the catholyte was studied and found to exceed that of composites synthesized with the use of H₂O₂ and evaporation of the solvent.     

Preparation of polyaniline-metal composite nanospheres by in situ microemulsion polymerization

Nanosized metal and polyaniline (PANi) composite spheres have been prepared via the polymerization of aniline using PdCl₂ or HAuCl₄ as the oxidant in a microemulsion system. The oxidization of aniline and the reduction of metal ion happened together during the reaction, yielding PANi and elemental metal simultaneously. The results of FTIR spectra suggested that the oxidation degree of PANi was affected by the initial ratio of metal ions to monomer in the microemulsion system. The PANi–metal nanospheres were characterized using X-ray photoelectron spectroscopy and the conductivity of the composite nanospheres was measured by conventional four-probe method. Scanning and transmission electron microscopy were used to show the morphology of the composites.     

The gibbs energies of transfer of calcium ions from water into water-acetone mixtures

Volta potential differences measured at 298.15 K were used to determine the real primary effect of the medium of calcium ions and the real Gibbs energy of transfer of Ca²⁺ from water into a mixed water-acetone (Me₂CO) solvent. The surface potential at the solvent/gas phase interface was found to be $\Delta \chi ^{Me_2 CO} = - 0.337V$ . This value was used to calculate the chemical thermodynamic characteristics of calcium ions. The thermodynamic characteristics of resolvation of the 2-1 electrolyte are compared with those obtained earlier for a 1-1 electrolyte.     

Composites of polyaniline and lead dioxide: preparation,characterization, and catalytic activity

This paper is devoted to the preparation of polyaniline/lead dioxide composites (PANI/PbO₂) via chemical oxidation of aniline in H₂SO₄ medium using β-PbO₂ as an oxidant. The parameters affecting the polymerization reaction are considered. These parameters are [aniline], amount of β-PbO₂, stirring time, and different acids. The prepared composites were characterized by SEM, FT-IR, XRD, TGA, DTA, and elemental analysis. From XRD and FT-IR spectra, it was concluded that high molecular weight polymer could be obtained with high aniline concentration, high amount of β-PbO₂, increasing polymerization time and polymerization of ANI at lower temperatures. Thermogravimetric study exhibited that the composite prepared using high amount of β-PbO₂ has a higher thermal stability. The application of the composites in the oxidative degradation of Alizarin yellow G and Acid alizarin violet N dyes exhibited good catalytic activity in presence of H₂O₂ as an oxidant. The reactions followed first-order kinetics and the rate constants were determined.     

Electrosynthesis of polyaniline in ionic liquid and its electrocatalytic properties

Ionic liquid like 1-butyl-3-methyl-imidazolium tetrafluorobrate ([BMIM]BF₄) has been used as solvent and electrolyte for the electropolymerization of aniline at glassy carbon electrode by cyclic voltammetry. Electrode modified with polyaniline (PAn) has obvious electrochemical activity in ionic liquid and acid solution (pH 0–4), and has significant electrocatalytic activity for redox reaction of catechol and hydroquione. __________ Translated from Journal of East China Normal University (Natural Science), 2005, 3 (in Chinese)     

RuO2-doping into high-aspect-ratio anodic TiO2 nanotubes by electrochemical potential shock for water oxidation

A novel method for homogenous incorporation of Ru (RuO₂, or RuO₃) into high aspect ratio anodic TiO₂ NTs was studied. TiO₂ NTs were prepared by anodization in HF based electrolyte, after which very short high applied potential, referred to as potential shock, was imposed on the TiO₂ NTs in KRuO₄ electrolyte. The high potential shock induced massive flow of RuO₄⁻ to positively-biased TiO2 NTs, resulting in the incorporation of Ru as a form of Ru, RuO₂, and RuO₃ in the TiO₂ NTs. Optimal potential shock, which allowed the most suitable amount and incorporation state of Ru catalysts in TiO₂ NTs, was determined by SEM, TEM, EDS, XPS, and LSV. It was demonstrated that electrochemical potential shock (simply imposed on the anodic TiO₂ for a few seconds in the electrolyte of KRuO₄) resulted in homogenous incorporation of Ru into the whole nanotubes without the need for any complicated steps or facilities.     

Fabrication of ruthenium-doped TiO2 electrodes by one-step anodization for electrolysis applications

Anodic TiO₂ films with a doping of Ru ions on the surface were coincidently prepared by facile one-step anodization for application of the electrode in electrolysis. We found that the amount of Ru ions on the surface of the oxide could be determined based on the applied potential in KRuO₄ electrolyte, which provided negative RuO₄^– ions through dissociation. Overpotentials for the evolution of both O₂ and Cl₂ were greatly reduced when the coincidently-Ru-doped TiO₂ was employed. The Ru-doped electrode prepared at 60 V showed the highest electrocatalytic activity due to the largest amount of Ru incorporation in the oxide.     

Ejection of Cluster Ions from a Liquid Beam of an Aniline-Propanol Solution Following Laser Photoionization

A simple technique of preparing a continuous laminar liquid flow in vacuum (liquid beam) was developed and combined with multiphoton ionization and a time-of-flight mass spectrometer. This technique was applied to the study on resonance photoionization of an aniline (AN)-propanol (PrOH) solution (0.1 – 0.3 M). Binary cluster ions of aniline and propanol, AN⁺(PrOH)_n (n ≤ 1), and protonated propanol cluster ions, H⁺(PrOH)_n (n ≤ 1), were observed as product ions in the gas phase. The relative intensities of AN⁺PrOH and those of H⁺(PrOH)₂ were measured as functions of the excitation laser power and the concentration of aniline in the propanol solution. The dependences of the ion intensities on the laser power and the AN concentration are explained in terms of a Coulomb ejection model, where the ions are ejected from the surface by Coulomb repulsion exerted from neighboring ions. It is also concluded that H⁺(PrOH)_n is produced by a proton transfer reaction from an aniline ion to solvent molecules in the solution.     

The stokes and robinson hydration theory: A modification with application to concentrated electrolyte solutions

The proposed extension to the Stokes and Robinson hydration theory is based on the premise that H₂O molecules of electrolyte solutions reside in two unique environments, the solvent environment and the hydration envelope (or sheath) environment. Changes to the chemical potential of H₂O in either environment result in redistribution of H₂O molecules between the environments; consequently hydration numbers of electrolytes decrease as the solvent activity decreases. An equation derived from the theory and containing two adjustable parameters reproduces electrolyte activity coefficients more accurately than does the original Stokes and Robinson equation.     

Conductivity increase effect in nanocomposite polymer gel electrolytes: manifestation in the IR spectra

Nanocomposite polymer electrolytes based on poly(ethylene glycol) diacrylate and 1 M LiBF₄ solution in γ-butyrolactone containing SiO₂ nanoparticles were studied by FT IR spectroscopy. Quantum chemical modeling of five different solvate complexes of ions composed of LiBF₄ with solvent molecules was carried out and their theoretical IR spectra were calculated. The compositions of the solvate complexes of LiBF₄ in the nanocomposite gel electrolyte were studied by comparing the experimental and theoretical IR spectra. It was concluded that the conductivity peak observed upon adding 2 wt.% SiO₂ is due to the appearance of mobile ions as a consequence of ionic dissociation on the surface of nanoparticles at their optimal configuration.

     

Carbon nanoparticles-induced formation of polyaniline nanofibers and their subsequent decoration with Ag nanoparticles for nonenzymatic H2O2 detection

The present communication reports on the preparation of polyaniline nanofibers (PANINFs) by chemical oxidative polymerization of aniline under rapid stirring using ammonium persulfate as the oxidant in acidic aqueous media in the presence of carbon nanoparticles. The subsequent treatment of such nanofiber with a AgNO₃ aqueous solution leads to in situ chemical reduction of Ag⁺ on them to form Ag nanoparticle-decorated PANINFs. The resultant composites show good catalytic activity toward the reduction of H₂O₂. An effective enzymeless H₂O₂ sensor based on such composites is also constructed. It exhibits a fast amperometric response time 2 s, and it has a linear detection range from 0.1 to 60 mM and detection limit of 0.9 μM at a signal-to-noise ratio of 3, respectively.     

Thermodynamics of Re-Solvation of Cadmium Ions in Water-Acetone Solvents

On the basis of a method of differences of Volta-potentials at 298.15 K the real primary effect of an environment of cadmium ions and the real Gibbs energy for the transport of Cd²⁺ out of water into a water-acetone solvent (Me₂CO) are determined. The surface potential at the nonaqueous solvent/gas phase interface \(\Delta \chi _{H_2 O}^S\) is obtained. This quantity is taken into account when calculating chemical thermodynamic characteristics for cadmium ions and the surface potential at the gas phase/acetone interface \(\Delta \chi ^{\operatorname{Me} _2 \operatorname{O} } = - 0.337\operatorname{V}\). Thermodynamic characteristics of the over-solvation of a II-I electrolyte with those for a I-I electrolyte are compared.     

Synthesis of conducting polyaniline using novel anionic Gemini surfactant as micellar stabilizer

The Gemini surfactant 9B-4-9B containing sodium sulfonate as hydrophilic head group was synthesized based on nonylphenol and characterized by FTIR, ¹H NMR spectroscopy and the surface tension measurement. The CMC and C₂₀ of the 9B-4-9B were smaller than that of sodium dodecylbenzene sulfonate and sodium dodecylsulfate, respectively, indicating excellent efficiency of micelle formation and reduced surface tension. Conducting polyaniline salts were synthesized by chemical oxidative micellar polymerization of aniline in water firstly using Gemini surfactant 9B-4-9B as the micelle stabilizer and ammonium peroxydisulfate as the oxidant at 0 °C. The stable polyaniline dispersions have been obtained when the molar ratio of the 9B-4-9B to aniline was equal to or above 0.5 used in the polymerization system. The obtained granular polyaniline particles with the size of 1-2 μm were characterized by FTIR, UV-Vis, SEM, WAXD and conductivity measurement.     

苯酚苯胺共聚物在304不锈钢电极表面的电化学合成及成膜微观结构分析

Electrochemical copolymerization of phenol and aniline was achieved on 304 stainless steel anodes in neutral water solution with an electrolyte of Na₂SO₄O₄. Compared with pit corro-sion potential of different copolymer coatings, the best solution composition was 0.09 mol/L phenol and 0.01 mol/L aniline. Through infrared spectrum analysis, polyaniline structure was proved in phenol-aniline copolymer, as well as more side chains. Scanning electron mi-croscope was used to analyze microstructure of copolymer coating, taking advantage of part solubility of phenol-aniline copolymer in tetrahydrofuran, the bifurcate network structure was observed. The copolymer coating microstructure was summarized, compared with the performance of polyphenol coatings, the reasons of corrosion resistance enhancement with the addition of aniline in electropolymerization reaction was assumed as well.     

Thermal and structural stability of composite systems based on polyaniline deposited on porous polyethylene films

Conducting composite systems containing polyaniline layers produced on the surface and inside the pores of polyethylene support have been prepared. Microporous polyethylene films were obtained by melt extrusion with subsequent annealing, uniaxial extension, and thermal fixation. Polyaniline layers were formed by in-situ polymerization of aniline onto polyethylene porous support placed into the aqueous reaction mixture. Structural and chemical transformations upon heating of these systems in air in free state and in vacuum under load have been investigated by thermo-mechanical tests, IR spectrometry, and electron microscopy. Changes in mechanical properties of composites after heating have been analyzed. Composite systems have been found to demonstrate a considerably lower shrinkage upon heating than microporous polyethylene substrates. It has been discovered that the composites preserve mechanical integrity on heating up to temperatures much higher than the polyethylene melting point. It is concluded that thermo-mechanical behaviour of the composites is determined by the space-continuous phase of polyaniline on the surface and in the bulk of polyethylene support.     

Solvolyse des Tetrathiocyanato-dianilino-chromat(III)-ions in Aceton—Wasser-Mischungen

The solvolysis of the [Cr(NCS)₄(aniline)₂]^? complex ion has been studied in various acetone-water mixtures in the presence of perchloric acid (10^?3–10^?1 mole/l). In acid solutions the first two NCS^? ions are exchanged, presumably, for water molecules and in parallel an aniline molecule for acetone, the latter in a second order reaction, accelerated by hydrogen ions. The exchange of the amine is followed by the substitution of the first two NCS^? ions. The third and fourth NCS^? ions are substituted only in neutral or weakly acid solutions. Kinetic parameters have been derived for the reactions mentioned above. The influence of solvent composition and of acidity is discussed.     

Electrochemical nanogravimetric study on the ruthenium(III) trichloride–polyaniline nanocomposite

Ruthenium(III) trichloride microcrystals were soaked in aniline and aniline/acetonitrile mixtures. In all cases, polyaniline (PANI) was formed as a result of the intercalation of aniline into the layered structure of RuCl₃ crystal and the reaction between aniline and the host material. The appearance of polyaniline was proven by infrared spectroscopy. The as-formed (PANI) _x ^z+(RuCl₃) _y ^z− nanocomposites were attached to gold surfaces and studied by cyclic electrochemical nanogravimetry. The sorption of aniline and its effect on the nanocomposites immobilized on gold were also studied in supporting electrolytes. The redox behaviour of the composite shows the electrochemical transformations of both polyaniline and RuCl₃. The redox waves of PANI are similar to those observed for very thin PANI films. It attests that the response is originated from monolayer-like PANI film situated between RuCl₃ layers. The transport of the charge-compensating ions reflects the variation of the oxidation states of both PANI and RuCl₃. The nanocomposites behave as self-doped layers in the potential region when both constituents are charged, i.e. PANI is partially oxidized while RuCl₃ is partially reduced, since the electroneutrality is assured by mutual charge compensation. When PANI is reduced, cations enter the layer to counterbalance the negative charge resulting from the reduction of Ru(III) to Ru(II). It was also found that the intercalation of water molecules is—albeit still substantial—smaller than that of pure RuCl₃ microcrystals, which is related to the presence of PANI between the RuCl₃ layers. Dedicated to Prof. Mikhail A. Vorotyntsev on the occasion of his 60th birthday