Facile synthesis and electrochemical capacitance of composites of polypyrrole/multi-walled carbon nanotubes

Composites of polypyrrole (PPy) and multi-walled carbon nanotubes (MWCNTs) were synthesized by a facile method involving one-step electrochemical deposition from a thin-layer of ionic liquid solution attached on a glassy carbon electrode. The morphology of the composites was characterized by field emission scanning electron microscopy, and the capacitance properties were investigated by cyclic voltammetry (CV). The charge-discharge behavior of the composites prepared in this work was examined by chronopotentiometry at a constant current density for multi-cycle scans. The results show that the PPy/MWCNT composites have a porous 3D nanostructure, with high specific capacitance (SC) of 890 F/g (for the mass of the PPy in the composites) calculated from CV at 2 mV/s in 1.0 M KCl. The stability of the composites in 1.0 M KCl electrolyte was also examined by multi-cycle CV and only 9% decrease of SC value was observed for the 1000 cycles.     

Electrochemical synthesis of polypyrrole in ionic liquids

Electrochemical synthesis of inherently conducting polymers such as polypyrrole is traditionally performed in a molecular solvent/electrolyte system such acetonitrile/lithium perchlorate. We report the use of ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide and N,N-butylmethylpyrrolidinium bis(trifluoromethanesulfonyl) amide, both as the growth medium and as an electrolyte for the electrochemical cycling of polypyrrole films. Use of the ionic liquid as the growth medium results in significantly altered film morphologies and improved electrochemical activities.     

Synthesis of novel sunflower-like silica/polypyrrole nanocomposites via self-assembly polymerization

Novel sunflower-like organic-inorganic composites consisting of spherical silica and smaller conductive polypyrrole particles were successfully prepared through an in situ self-assembly polymerization process by choosing chitosan as a modifying agent of silica surface. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that on the surface of individual silica particle polypyrrole nanoparticles were anchored perfectly. The sunflower-like silica-polypyrrole composites exhibited conductivity of 8 S cm⁻¹ and colloid stability because of the special surface morphology. Adsorbed chitosan chain may play a dual-role of both providing the active sites for formation of the polypyrrole particles on silica and acting as a stabilizer of the silica-polypyrrole particles. Hydrogen-bonding interaction between the acetylamino group of chitosan and hydrogen atom on nitrogen of polypyrrole is a determining parameter in the former case.     

In situ electropolymerization of conducting polypyrrole/carbon nanotubes composites on stainless steel: Role of carbon nanotubes types

In situ electropolymerization was used to prepare polypyrrole-oxidized multi-walled carbon nanotubes and polypyrrole-oxidized single-walled carbon nanotubes composites on a stainless steel surface from 0.1 M oxalic acid by using cyclic voltammetry. The electropolymerization process was investigated and discussed, and the results showed that the addition of the oxidized carbon nanotubes greatly enhanced the electropolymerization process, especially in the case of oxidized single walled carbon nanotubes. The results also showed that increasing the pyrrole monomer concentration leads to increasing the amount of polypyrrole electrodeposited, and this is more pronounced in the presence of the carbon nanotubes. The electropolymerization process was mainly under diffusion control as the process was inhibited by increasing the scan rate. In general, the presence of oxidized carbon nanotubes improved the electropolymerization of the polypyrrole and greatly enhanced its thermal and morphological properties.     

Water/ionic liquid/organic three-phase interfacial synthesis of coral-like polypyrrole toward enhanced electrochemical capacitance

Two interfacial synthesis strategies are proposed to synthesize polypyrrole samples for electrochemical capacitors (ECs). In contrast to water/organic two-phase route, unique water/ionic liquid (IL)/organic three-phase interface strategy is first performed to prepare coral-like polypyrrole with even better electrochemical capacitance, where 1-Ethyl-3-methylimidazolium tetrafluoroborate IL, as a “buffering zone”, is set between the water and organic phases to control the morphology and micro-structure of the polypyrrole phase during polymerization. The polypyrrole synthesized by three-phase interfacial route owns more ordered structure, less charge transfer resistance and better electronic conductivity, compared with two-phase method, and delivers larger specific capacitance, higher rate performance and better electrochemical stability at large current densities in 3 M KCl aqueous electrolyte.     

Electrochemical polymerization of pyrrole in supercritical carbon dioxide-in-water emulsion

Supercritical carbon dioxide is an environmentally benign solvent but its low polarity limits electrochemical reactions in it. We now report the electrochemical polymerization of pyrrole in a supercritical carbon dioxide-in-water (C/W) emulsion in the presence of a surfactant. Black polypyrrole films were formed on Pt electrodes, whose conductivity was comparable with non-oriented polypyrrole prepared in conventional solvents. The structure of the polypyrrole films was confirmed by IR and Raman spectroscopic measurements. p-Toluenesulfonic acid was a suitable supporting electrolyte among the electrolytes examined for the electrochemical polymerization in the C/W emulsion. A typical nodular morphology was observed on the basis of the SEM and AFM measurements. Confocal scanning microscope revealed the formation of a fine uneven texture on the film prepared in the C/W emulsion.     

Interfacial polymerization of pyrrole and in situ synthesis of polypyrrole/silver nanocomposites

We present a new synthetic approach leading to the formation of polypyrrole architectures in submicron level and to silver/polypyrrole nanocomposites via an interfacial polymerization in a water/chloroform interface. The oxidizing agent was either Ag(I) or Fe(III). In the first case, silver nanoparticles resulted. The mean diameter of the polypyrrole structures is in the range of 200-300 nm according to the addition or not of various surfactants. The progress of the reaction was studied by UV-visible spectroscopy, which also revealed the formation of a polaron band during the growth of the oligomers. The crystal structure of the polymers was examined by X ray diffractometry and all samples appeared to be amorphous, while the samples were further characterized by thermogravimetric analysis and FT-IR spectroscopy.     

The corrosion-inhibiting effect of polypyrrole films doped with p-toluene-sulfonate,benzene-sulfonate or dodecyl-sulfate anions,as coating on stainless steel in NaCl aqueous solutions

This article presents a study of the conditions for electro-synthesis of polypyrrole (PPy) films on stainless steel, in the presence of the anions p-toluene-sulfonate (pTS), benzene-sulfonate (BS) or dodecyl-sulfate (DS). Cyclic voltammetry (CV) was used in the synthesis of the polypyrrole films on the stainless steel (SS). These polymeric films were characterized by IR and UV–vis spectroscopy and their morphology and thickness were analyzed by scanning electron microscopy (SEM). Their performance as protective films against corrosive processes presented by the SS/PPy-pTS, SS/PPy-BS or SS/PPy-DS systems was evaluated in 0.1 M NaCl aqueous solution. The study of the corrosion processes of the stainless steel/polymer systems was conducted through measurements of open circuit potential (E_OCP), polarization curves (PC) and electrochemical impedance spectroscopy (EIS). The results showed that the protective capacity of these polymeric systems on stainless steel, mainly with regard to pitting, depends on the nature of the anion dopant used during electro-synthesis of the PPy film. The best performance was seen with the dopants pTS and BS.     

Synthesis of polypyrrole/indium tin oxide nanocomposites via miniemulsion polymerization

Polypyrrole/indium tin oxide nanocomposites were synthesized via in situ miniemulsion polymerization of pyrrole monomer in the presence of indium tin oxide nanoparticles. Different nanocomposites were synthesized by different loadings of nano indium tin oxide. The morphology and nanoparticles distribution of the nanocomposites were characterized by electron microscopy. The results of XRD and TEM analysis showed that indium tin oxide nanoparticles were well placed in the polymeric structure of latex. FTIR analysis was used for the characterization of synthesized polypyrrole and its nanocomposites. TGA analysis was performed to investigate the thermal behavior of pristine polypyrrole and its nanocomposites. Conductivities of nanocomposites were measured by 4-point probe method and compared to the neat polymer.     

Characterisation and corrosion studies of steel electrodes covered by polypyrrole/phosphotungstate using Electrochemical Impedance Spectroscopy

Polypyrrole/PW₁₂O₄₀³⁻ hybrid material was electrosynthesised on carbon steel electrodes in acetonitrile medium. The coatings obtained were characterised by Electrochemical Impedance Spectroscopy (EIS). On free-standing polypyrrole films the electrical response was mainly due to ion–ion charge transfer resistance, with a value of 175 Ω cm². A value of 2 × 10⁻⁵ S/cm was determined for the hybrid material conductivity. A charge transfer resistance about 7000 Ω cm² was obtained due to steel/oxide interface. Corrosion tests showed an important improvement in the protection against corrosion when the carbon steel electrodes were coated by these polymeric films.     

聚吡咯纳米粒子的制备与应用

综述了导电性聚吡咯纳米粒子的制备方法、特殊性能与应用。     

Nano-composite of polypyrrole/modified mesoporous carbon for electrochemical capacitor application

Nano-thin polypyrrole (PPy) layers were coated on chemically modified ordered mesoporous carbon (m-CMK-3) by an in situ chemical polymerization. Structural and morphological characterizations of m-CMK-3/PPy composites were carried out using field emission scanning electron microscopy. Pseudo-capacitive behavior of the deposited PPy layers on m-CMK-3 was investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. As results of this study, the thin layer of PPy in the composite electrode was effective to obtain fully reversible and very fast Faradaic reaction. A maximum discharge capacity of 427 F g⁻¹ or 487 F g⁻¹ after correcting for weight percent of PPy phase at the current density of 5 mA cm⁻², could be achieved in a half-cell setup configuration for the m-CMK-3/PPy composites electrode, suggesting its potential application in electrode material for electrochemical capacitors.     

分级多孔聚吡咯膜的界面自组装合成与电化学电容性

通过界面自组装聚合,在长链表面活性剂OP10的辅助下成功制备了分级多孔结构聚吡咯膜。对所得聚吡咯的分子结构、微观形貌和电化学性能分别进行了表征和研究。结果表明：界面聚合中引入OP10对聚吡咯的分子结构并没有影响,但对其微观形貌却具有重要作用。当OP10的用量优化为0.02 g时,聚吡咯可自组装形成分级多孔结构,既有纳米孔（约100 nm）,也有亚微米孔（200~1000 nm）和微米孔（1~3.5 μm）。由于相对较高的活性表面积和总孔体积,分级多孔聚吡咯作为电极材料最大比电容可达357 F·g^-1,比相同条件下传统界面法制备的聚吡咯高70%以上。此外,2000次充放电循环后该材料仍保持初始比电容的87.6%,表明其优异的循环稳定性。     

Electrochemical synthesis and redox behaviour of polypyrrole coatings on copper in salicylate aqueous solution

In this work, polypyrrole (PPy) coatings have been successfully electrodeposited on copper substrates from aqueous salicylate solutions. Homogenous and uniform films can be grown under galvanostatic or potentiostatic control without noticeable substrate dissolution. The redox behaviour obtained for the films is similar to that displayed by PPy grown under the same conditions on noble metals. Strong adherence to copper is observed as far as PPy is in its oxidised state but it is lost when the system is subjected to potentials lower than −0.5 V versus saturated calomel electrode (SCE).     

Experimental investigations of semi-crystalline plasma polymerized polypyrrole for surface coating

Plasma polymerized thin film of conducting polypyrrole were deposited at room temperature by plasma enhanced chemical vapor deposition method using pyrrole monomer as precursor. The radio frequency (RF: 13.56 MHz, power supply: 30 W) was applied at constant argon gas pressure for the formation of plasma. The as grown thin films of polypyrrole have been characterized by ellipsometry, Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy, atomic force microscopy (AFM), X-ray diffractometry (XRD) and high-resolution transmission electron microscopy (HRTEM). UV–vis spectra showed the optical energy band gap of 2.3 eV. XRD pattern of plasma polymerized polypyrrole has revealed a clear peak at inter-planer separation of 0.687 nm. It was also noticed by HRTEM analysis that the distinguished reflection at d =  0.687 nm has a broadening effect that may be correlated with the crystallinity of the material.     

Electrochemical synthesis of selenium nanotubes by using CTAB soft-template

The single-crystalline Se nanotubes were synthesized on the surface of Au sheet electrode by cyclic voltammetry. In synthesis process, cetyltrimethyl ammonium bromide (CTAB) was used as soft-template. The formation mechanism of Se nanotubes was discussed. Furthermore, the deposits with other morphologies were also obtained by modulating parameters in the synthesis process. The products as-prepared were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and laser Raman spectrograph (LRS). The electrochemical behavior of the Se nanotubes was studied by the linear scan voltammetry.     

Synthesis and self-assembly behaviors of three-armed amphiphilic block copolymers via RAFT polymerization

The novel trifunctional reversible addition-fragmentation chain transfer (RAFT) agent, tris(1-phenylethyl) 1,3,5-triazine-2,4,6-triyl trithiocarbonate (TTA), was synthesized and used to prepare the three-armed polystyrene (PS₃) via RAFT polymerization of styrene (St) in bulk with thermal initiation. The polymerization kinetic plot was first order and the molecular weights of polymers increased with the monomer conversions with narrow molecular weight distributions (M_w/M_n ≤ 1.23). The number of arms of the star PS was analyzed by gel permeation chromatography (GPC), ultraviolet visible (UV-vis) and fluorescence spectra. Furthermore, poly(styrene-b-N-isopropylacrylamide)₃ (PS-b-PNIPAAM)₃, the three-armed amphiphilic thermosensitive block copolymer, with controlled molecular weight and well-defined structure was also successfully prepared via RAFT chain extension method using the three-armed PS obtained as the macro-RAFT agent and N-isopropylacrylamide as the second monomer. The copolymers obtained were characterized by GPC and ¹H nuclear magnetic resonance (NMR) spectra. The self-assembly behaviors of the three-armed amphiphilic block copolymers (PS-b-PNIPAAM)₃ in mixed solution (DMF/CH₃OH) were also investigated by high performance particle sizer (HPPS) and transmission electron microscopy (TEM). Interestingly, the lower critical solution temperature (LCST) of aqueous solutions of the three-armed amphiphilic block copolymers (PS-b-PNIPAAM)₃ decreased with the increase of relative length of PS in the block copolymers.     

Electrochemical investigations into polypyrrole/aluminum flake pigmented coatings

In this study polypyrrole was synthesized in the presence of aluminum flake to produce polypyrrole/aluminum flake hybrids. The resulting flakes were incorporated into a standard epoxy coating at relatively high pigment volume concentrations with the end goal of producing a conducting film capable of providing corrosion inhibition to an aluminum alloy. To further investigate the coatings, electrochemical impedance spectroscopy (EIS) was used to characterize the effects of the pigment volume concentration (PVC) on the impedances of the coatings. Additionally, the nature of the polypyrrole, chemical composition, and surface morphology of the hybrid were characterized by a density test and scanning electron microscopy (SEM).     

New pathway for the synthesis of gold and silver bimetallic nanocomplexes and their derivatives of polypyrrole nanorods (TM04096)

We report here the first electrochemical pathway to prepare Au- and Ag-containing bimetallic nanocomplexes with a mean diameter of 5 nm in 0.1 M HCl aqueous solutions without addition of any stabilizer. First, a silver substrate was roughened by a triangular-wave oxidation-reduction cycle (ORC) in an aqueous solution containing 0.1 M HCl. Silver-containing complexes were left in the solution after the ORC treatment. Then a gold substrate was subsequently roughened by the similar ORC treatment in this solution. Encouragingly, polypyrrole (PPy)-coated Au and Ag bimetallic nanocomposites with a nanorod structure and a diameter smaller than 15 nm can be prepared by the formation of self-assembled monolayers and orderly autopolymerization of pyrrole monomers on these bimetallic nanocomplexes, and further link them together.