Resistance of the Polypyrrole/Polyimide Composite by Electrochemical Impedance Spectroscopy

Electrically conducting polymers are promising for applications in polymer based charge storage devices and for membrane applications. Composing polypyrrole with polyimide improves mechanical properties of polypyrrole and affects the electrochemical properties of the composite. In this paper resistance to ion flow of pure polyimide and of the polypyrrole/polyimide composite were studied by electrochemical impedance spectroscopy, comparatively, as a function of applied potentials and of amount of polypyrrole. Electron scanning microscopy and surface mapping were used for surface characterization. Observed behavior was explained with electroactivity of the components of the composite. Conclusions about the effect of polypyrrole on the structure and resistance were made.     

Electrochemical Impedance Spectroscopic Analysis of Sensitization-Based Solar Cells

Electrochemical impedance spectroscopy (EIS) is a very powerful tool for elucidation of charge transfer and transport processes in sensitization-based solar cells (e.g., dye-sensitized solar cells [DSSCs], quantum dot-sensitized solar cells [QDSSCs], and perovskite solar cells [PSCs]). EIS measures the electrochemical response to small amplitude AC signals over a wide range of frequencies. Analysis of the EIS response provides information about the corresponding parameters of the cells. Here, we review the fundamentals of EIS, charge transport kinetic processes, and equivalent circuit models of sensitization-based solar cells and use these concepts to explain the EIS spectra of DSSCs, QDSSCs, and PSCs. This review will be very useful for understanding the fundamental charge transfer and transport processes in different sensitization-based solar cells and the use of an equivalent circuit model to interpret the observed charge transfer and reactions.     

Impedance spectroscopy studies on samarium and sodium substituted strontium bismuth titanate (SBTi)

Sr_1-x Sm_xNa_xBi₄Ti₄O₁₅ lead-free piezoelectric ceramics are prepared by solid-state sintering method using high energy Ball- Mill and ground for 10 h. The single phase of the compound is confirmed by X-ray Diffraction and highest intensity peak (1 1 0) is observed at 30°. Diffraction peaks shifted towards higher angles with an increasing concentration of Sm³⁺ and Na¹⁺ of SBT. Grains orientation and grain size are analyzed by Scanning Electron Microscope. Temperature and frequency dependent AC conductivity studies are carried out using impedance spectroscopy in the temperature range of 30 °C–650 °C using Wayn-Kerr LCR meter. At lower frequencies, conductivity is independent of frequency. The variation of Z″ with frequency shows peaks shifting towards higher frequencies with an increase of temperature. The resistance of grains (R_g), grain boundaries (R_gb) are calculated and it is found that grain resistance is greater than grain boundary resistance (R_g > R_gb). Relaxation times of grain and grain boundaries are calculated.     

Impedance spectroscopy study of electrochromism in sputtered iridium oxide films

The a.c. impedance response of sputtered iridium oxide films (SIROFs) was studied at room temperature in 1M H₂SO₄ between 1mHz and 50mHz. The spectra were recorded as a function of applied potential in the range of electrochromic properties from 0.0 to 1.0V vs SCE and before and after an electrochemical treatment consisting of alternatively colouring and bleaching the electrode. The spectra were analysed with help of an equivalent circuit. Between 0.4 and 1.0V, the spectra can be interpreted as due to electrochemical proton insertion in a single phased compound. From the data, hydrogen chemical diffusion coefficients with values ranging from 2 × 10^–8 to 1.1 × 10^–7cm²s^–1 are found. It is shown that this parameter increases fourfold after the cycling treatment and significantly decreases with the amount of inserted hydrogen. Below 0.4V spectrum changes are observed over the intermediate frequency range studied, indicating some changes of the interfacial reactivity which remain to be clarified.     

Protein adsorption materials based on conducting polymers: polypyrrole modified with ω‐(N‐pyrrolyl)‐octylthiol

In order to fabricate a new polymer matrix for application in biochips and to understand the mechanism of adsorption of proteins on conducting polymers, we prepared polypyrrole (PPy) functionalized with ω‐(N‐pyrrolyl)‐octylthiol moieties. The chemical structure of the polymer could be controlled by varying the concentration of pyrrole added as the monomer. Initially, ω‐(N‐pyrrolyl)‐octylthiol was self‐assembled into a monolayer on a gold surface. Thereafter, a layer of uniform and smooth PPy was obtained by the chemical copolymerization of pyrrole and the ω‐(N‐pyrrolyl)‐octylthiol. Bovine serum albumin (BSA) adsorption on the polymer was investigated using surface plasmon resonance spectroscopy and cyclic voltammograms. The chemical structure and monomer components of the as‐prepared films were characterized using Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. Water contact angle measurements were used to assess the surface wettability of the films throughout the preparative procedure. The kinetics of BSA adsorption onto the polymer could be controlled by varying the copolymer thickness and the pH value of the buffer solutions used. Moreover, the electroactivity was changed upon BSA binding. The results suggest that the new conducting polymer may potentially be applied as a more sensitive and reliable matrix in protein sensors. Copyright © 2011 Society of Chemical Industry     

Electropolymerization of N‐hydroxyethylcarbazole on carbon fiber microelectrodes

N‐Hydroxyethylcarbazole (EtOHCz) was electropolymerized on carbon fiber microelectrodes (CFMEs). The polyEtOHCz‐modified CFME was characterized with FTIR‐ATR, scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The polymer/CFME electrode exhibited the capacitive behavior and also good stability up to 2.0 V. The presence of hydoxylic group of the monomer seems to be an advantage on polymerization because of the unpaired electrons of oxygen, which would make ease at first stage for the adsorbtion on carbon fiber. The estimated value of the low‐frequency redox capacitance (C_LF) was found to increase with increasing dc potential. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Electrochemical polymerization and characterization of polyether‐substituted aniline derivatives

New compounds consisting of aniline units linked by polyether bridges have been synthesized and their electrochemical polymerization was performed via constant potential electrolysis and cyclic voltammetry in an aqueous solution containing 3.0 mol L^?1 H₂SO₄. Chemical polymerization was carried out using (NH₄)₂S₂O₈ as oxidizing agent. It was found that both methods gave the same polymer product without any cleavage of the polyether bridge between aniline rings. The polymers were characterized using the Fourier transform infrared spectroscopic technique and the thermal behavior of electrochemically prepared polymers was investigated using thermogravimetric analysis. Spectroelectrochemical properties of the films were investigated using the in situ UV‐visible spectroscopic technique. Copyright © 2007 Society of Chemical Industry     

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。     

Electrochemically synthesized polypyrrole and Cu‐plated nylon/spandex for electrotherapeutic pad electrode

Electroconductive fabrics were prepared to improve the properties of conductive electrode pad material used for electrotherapy when it is subjected to various movements of the human body. Highly stretchable and conductive fabrics were prepared by in situ electrochemical polymerization of polypyrrole (PPy) on nylon/spandex stretchable fabric in aqueous solutions with 0.05M pyrrole and 0.05M anthraquinone‐2‐sulfonic acid, sodium salt monohydrate (AQSA) at room temperature for 2 h. Electroless Cu plating was also applied after chemical polymerization of PPy to improve the conductivity of the fabric pad. Performance of prepared stretchable conductive fabric pad was evaluated in terms of conductivity changes as a function of extension and continuous current application time, and clinical test. As a result, the fabric conductivity was well maintained with extension up to 60% and prolonged treatment time over 30 min. The effect of transcutaneous electrical nerve stimulation (TENS) was observed with prepared TENS pad in this study and conventional TENS pad for medical use. The significant effect of TENS was observed with a pad made of conductive fabric by Cu plating and a conventional TENS pad (P < 0.05, respectively). Even though the efficiency of an experimental pad made of fabric composite with electrochemically polymerized PPy was not as good as conventional TENS pad for medical use in this experiment, it can possibly be used for other applications where relatively low‐strength electrical pulse is required. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 4064–4071, 2004     

Impedance spectroscopy study on polymer‐derived amorphous SiAlCO

The electric behaviors of both free‐carbon phase and ceramic phase in polymer‐derived amorphous silicoaluminum oxycarbide were studied by impedance spectroscopy. The results revealed that the resistance of both ceramic phase and free‐carbon phase are similar to each other and decreased with pyrolysis temperature. Meanwhile, the ceramic phase showed higher capacitance than the free‐carbon phase. With increasing pyrolysis temperature, the capacitance of the ceramic phase drastically decreased, but that of the free‐carbon phase remained similar. Each phase exhibited a relaxation process, which moved to higher frequency with increasing pyrolysis temperature. The results are correlated with the structural evolution of the two phases.     

Conducting composites of poly(N‐vinylcarbazole), polypyrrole,and polyaniline with 13X‐zeolite

N‐vinylcarbazole (NVC) was polymerized by 13X zeolite alone in melt (65°C) or in toluene (110°C) and a poly(N‐vinylcarbazole) (PNVC)‐13X composite was isolated. Composites of polypyrrole (PPY) and polyaniline(PANI) with 13X zeolite were prepared via polymerization of the respective monomers in the presence of dispersion of 13X zeolite in water (CuCl₂ oxidant) and in CHCl₃ (FeCl₃ oxidant) at an ambient temperature. The composites were characterized by Fourier transform infrared analyses. Scanning electron microscopic analyses of various composites indicated the formation of lumpy aggregates of irregular sizes distinct from the morphology of unmodified 13X zeolite. X‐ray diffraction analysis revealed some typical differences between the various composites, depending upon the nature of the polymer incorporated. Thermogravimetric analyses revealed the stability order as: 13X‐zeolite > polymer‐13X‐zeolite > polymer. PNVC‐13X composite was essentially a nonconductor, while PPY‐13X and PANI‐13X composites showed direct current conductivity in the order of 10^?4 S/cm in either system. However, the conductivity of PNVC‐ 13X composite could be improved to 10^?5 and 10^?6 S/cm by loading PPY and PANI, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 913–921, 2006     

Impedance spectroscopy study of anodic growth of thick zirconium oxide films in H2SO4, Na2SO4 and NaOH solutions

Anodic zirconium oxide films were grown potentiodynamically at a constant sweep rate up to the breakdown potential on rod electrodes made of 99.8% metallic zirconium. Different media of different pH were tested, namely 0.5 M H₂SO₄ (pH 0.3), 0.1 M Na₂SO₄ (pH 9) and 0.1 M NaOH (pH 13). By electrochemical impedance spectroscopy and scanning electron microscopy the oxide film thickness was monitored during the voltage scan. The behaviour was found to be different in the presence and absence of sulphate anions. In the presence of SO₄²⁻, the films were dense but breakdown occurred at 300–340 nm. In NaOH, two relaxations appeared above 50 V and were ascribed to a bi-layered coating structure and the maximum layer thickness was 720 nm before breakdown.     

电化学合成重铬酸钠阳极稳态极化及交流阻抗法研究

针对重铬酸钠传统生产技术存在问题,提出电化学合成重铬酸钠的绿色新技术,阳极为自制钛基多元金属氧化物复合电极,所用阳极液为铬酸钠水溶液.阳极既是电催化合成过程的催化剂,又是电催化反应进行的场所.根据电催化合成重铬酸钠体系的特点,运用稳态极化曲线和交流阻抗技术研究了阳极反应动力学及电化学行为.实验测得阳极反应活化能等电极反...     

Electrochemically stimulated 2‐ethylhexyl phosphate (EHP) release through redox switching of conducting polypyrrole film and polypyrrole/poly (N‐methylpyrrole) or self‐doped polyaniline bilayers

2‐Ethylhexyl phosphate (EHP) released from poly(pyrrole 2‐ethylhexyl phosphate) (PP‐EHP) was investigated at open circuit and compared with electrochemically stimulated release during potential cycling. It was found that the fast EHP release from the PP‐EHP single layer is substantially retarded and that amounts of spontaneously and electrochemically released EHP can be reduced by constructing bilayers, consisting of a PP‐EHP inner layer and a poly(N‐methylpyrrole)‐poly(styrene sulfonate) (PNMP‐PSS) or self‐doped poly(aniline) sulfonate (SPANI) as the outer films. The presence of outer film over the PP‐EHP allowed surface‐property modification, as well as the control of the rate of EHP release, while electrochemically stimulated EHP release from inner films was not substantially hampered by the outer layer. The quantity of the EHP released was investigated using UV‐vis spectrophotometery and an electrochemical quartz‐crystal microbalance (EQCM) during reduction of PP‐EHP from single layer and bilayers through electrochemical stimulation. EHP was reincorporated to the inner film by applying an anodic potential and then the release of EHP was performed again. The results showed that the outer film could act as a barrier to ion‐and solvent‐transport between the inner film and electrolyte, yielding a more balanced counter‐directional movement of anions. © 2002 Society of Chemical Industry     

Conduction mechanism in H‐type polysiloxane‐polypyrrole block copolymers

Conducting polymers of polysiloxane‐polypyrrole were synthesized by electropolymerization of the pyrrole monomer through pyrrole moieties in N‐pyrrole‐terminated polysiloxanes. Sodium paratoluene sulfonate was used as the electrolyte. Scanning electron microscopy (SEM) was used to determine the surface morphology of the films. The room‐temperature conductivity values of the films were found to be in the range of 1.9–4.4 × 10^?4 (Ω cm)^?1, depending on the supporting electrolyte concentration. The temperature dependence of the dc conductivities of the copolymers having different dopant concentrations was investigated within the temperature range of 100–320 K. The evaluated parameters showed that the electrical transport is dominated by variable range hopping. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 52–56, 2002     

Molecular tailoring to improve polypyrrole hydrogels’ stiffness and electrochemical energy storage capacity

This research looks at ways of tailoring and improving the stiffness of polypyrrole hydrogels for use as flexible supercapacitor electrodes. Molecules providing additional cross-linking between polypyrrole chains are added post-polymerisation but before gelation, and are found to increase gel stiffness by up to 600%, with the degree of change dependent on reactant type and proportion. It was also found that addition of phytic acid led to an increase in pseudocapacitive behaviour of the hydrogel, and thus a maximum specific capacitance of 217.07 F·g⁻¹ could be achieved. This is an increase of 140% compared to pristine polypyrrole hydrogels produced by this method.     

电化学阻抗谱在电沉积研究中的应用(一)

介绍了电化学阻抗谱在各种金属及合金的电沉积研究中的应用。文章分3期连载。第一部分介绍了电化学阻抗谱的基础知识,包括复数、复阻抗的概念,以及在各种常见条件下电解池的等效电路图。     

Impedance spectroscopy study of saturated mortar samples

Mortar samples saturated with different solutions (deionised water, 0.5 M NaCl and 1 M NaCl) are studied to quantify microstructural changes induced by weathering of concrete in near-neutral solutions containing chlorides. The study is based on physical and electrochemical techniques. Mercury intrusion porosimetry is employed to quantify porosity and pore size distribution, and impedance spectroscopy as a non-destructive technique able to give information on structural changes. SEM imaging, XRD, and EDX characterisation allow elucidating the causes of the observed structural changes.Portlandite leaching tends to increase porosity. Nevertheless, the leaching process towards near-neutral solutions makes resistivity to increase. The presence of chlorides induces Friedel's salt formation, a slow process associated to the development of small size pores (around 10 nm).Impedance spectroscopy in the frequency range 10⁻² to 10² MHz is successfully employed to follow Friedel's salt formation and pore network development in mortars.     

Synthesis and characterization of a new conducting polymer based on 4‐(2,5‐di‐2‐thiophen‐2‐yl‐pyrrol‐1‐yl)‐phthalonitrile

A new conducting polymer was synthesized by electrochemical polymerization of 4‐(2,5‐di‐2‐thiophen‐2‐yl‐pyrrol‐1‐yl)‐phthalonitrile (SNS‐PN). Electrochemical polymerization of SNS‐PN was performed in acetonitrile/0.2M LiClO₄ solvent/electrolyte couple. Characterizations of the resulting polymer P(SNS‐PN) were carried out by cyclic voltammetry, UV–vis, and Fourier transform infrared (FTIR) spectroscopic techniques. Spectroelectrochemical studies revealed that P(SNS‐PN) has an electronic band gap of 2.45 eV and exhibits electrochromic behavior. The switching ability of polymer was also monitored and the percentage transmittance change (ΔT%) was found as 24%. It is also found that P(SNS‐PN) is fluorescent and its fluorescence intensity enhances in the presence of cations. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009