Improved electrochemical performances of polyaniline by graphitized mesoporus carbon: Hybrid electrode for supercapacitor

In this work, graphitized mesoporus carbon (GMC) was used to increase the specific capacitance and cycle stability of polyaniline (PANI). Hybrid material of polyaniline‐graphitized mesoporus carbon (GMCP) was prepared by in situ chemical polymerization of aniline in presence of sulphuric acid using ammonium persulfate oxidant with various amounts of GMC. Formation of hybrid sample was confirmed from X‐ray diffraction, and the composite sample was stable up to 250°C. Morphology, crystalline nature, and electrochemical performance of GMCP were compared with that of its individual components, GMC and PANI. GMC showed particle morphology and PANI showed nanofiber morphology. GMCP2 composite showed nanofibrous form of PANI grown on GMC (spherical form) along with PANI nanofibers. Higher crystallinity was obtained for GMCP than that of PANI. Cycling stability of GMCP2 was carried up to 12,000 cycles at 1200 W kg^?1 and the retention capacitance was 66% of its original capacitance of 243 F g^?1. With the same power density, GMC showed less capacitance value of 53 F g^?1 with 92% retention and PANI showed capacitance of 187 F g^?1 and it underwent 1500 cycles only. Higher supercapacitor performance was obtained for GMCP composite compared to that of its components, PANI and GMC. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42540.     

Electrospun polyaniline nanofibers web electrodes for supercapacitors

Polyaniline nanofibers (PANI‐NFs) web are fabricated by electrospinning and used as electrode materials for supercapacitors. Field‐emission scanning electron microscope micrographs reveal nanofibers web were made up of high aspect ratio (>50) nanofibers of length ～30 μm and average diameter ～200 nm. Their electrochemical performance in aqueous (1M H₂SO₄ and Na₂SO₄) and organic (1M LiClO₄ in propylene carbonate) electrolytes is compared with PANI powder prepared by in situ chemical oxidative polymerization of aniline. The electrochemical properties of PANI‐NFs web and PANI powder are studied using cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. PANI‐NFs web show higher specific capacitance (～267 F g^?1) than chemically synthesized PANI powder (～208 F g^?1) in 1M H₂SO₄. Further, PANI‐NFs web demonstrated very stable and superior performance than its counterpart due to interconnected fibrous morphology facilitating the faster Faradic reaction toward electrolyte and delivered specific capacitance ～230 F g^?1 at 1000th cycle. Capacitance retention of PANI‐NFs web (86%) is higher than that observed for PANI powder (48%) indicating the feasibility of electro spun PANI‐NFs web as superior electrode materials for supercapacitors. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Fabrication and electrochemical characterization of polyaniline nanorods modified with sulfonated carbon nanotubes for supercapacitor applications

The novel composites of sulfonated multi-walled carbon nanotubes (sMWCNTs) modified polyaniline (PANI) nanorods (PANI/sMWCNTs) were synthesized successfully by in situ oxidative polymerization method in the HClO₄ solution. FTIR and Raman spectra revealed the presence of π–π interaction between the PANI and the sulfonated carbon nanotubes and the formation of charge transfer composites. It was found that the specific capacitance of the PANI/sMWCNT composites was markedly influenced by their morphological structure and the content of PANI which was coated onto the sMWCNT. The specific capacitance of the PANI/sMWCNT composite exhibited a maximum value of 515.2 F g⁻¹ at the 76.4 wt% PANI. The charge–discharge tests showed the PANI/sMWCNT composites possessed a good cycling stability (below 10% capacity loss after 1000 cycles) compared to PANI nanorods.     

Novel chemically synthesized polyaniline electrodes containing a fluoroboric acid dopant for supercapacitors

The performance of chemically synthesized dual‐acid‐doped polyaniline (PANI) electrode material was investigated for supercapacitors for the first time. Three different grades of PANI‐containing fluoroboric acid (HBF₄) as one of the dopants were prepared by a chemical polymerization method. PANI–dodecylhydrogen sulfate–HBF₄ salt was synthesized by an emulsion polymerization pathway. A PANI–HBF₄–sodium tetrafluoroborate composite and PANI–HBF₄ salt were prepared from different modifications of dopants by a dedoping–redoping process. Capacitative behaviors of the three grades of PANI electrode materials were investigated. Among the three different grades of PANI, PANI–HBF₄ electrode showed the best performance in terms of conductivity (2.3 × 10^?1 S/cm), specific capacitance of the supercapacitor (140 F/g), specific energy (9.6 W h/kg), and specific power (58.8 W/kg). An increase in the capacitance of PANI–HBF₄ was achieved, which identified the significant contribution of the dedoping–redoping processes in the PANI system for supercapacitors. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The unique morphology role of thorn surface in determining electrochemical performance of polyaniline nano‐fibers via one‐step method

Polyaniline nano‐fibers with thorn surface morphology (T‐PANI) were synthesized by one‐step polymerization with adding additional aniline at later stage of chemical oxidation synthesis. In order to investigate the morphology role in determining electrochemical performance, the nano‐fibers PANI without thorn (PANI) was synthesized by the same polymerization process but at different time to add additional aniline. Material structures were characterized by field emission scanning electron microscope and Brunauer‐Emmett‐Teller method, and electrochemical performance was tested through cyclic voltammograms, galvanostatic charge‐discharge and electrochemical impedance spectroscopy. The data showed that the specific capacitance of T‐PANI was 443 F g^?1 at 5 mA cm^?2, which was much more than that of PANI (338 F g^?1 at 5 mA cm^?2). The solution resistance, charge transfer resistance, and diffuse resistance of T‐PANI were also lower than these of PANI. The results indicate that the thorn surface structure plays an important role in determining the electrochemical performance of polyaniline, which attribute to the improvements in pore size, pore distribution, special surface area, and conductivity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42266.     

Facile synthesis of graphene/polyaniline composite hydrogel for high-performance supercapacitor

The graphene/polyaniline (PANI) composite hydrogel was successfully prepared by a one-step hydrothermal method. The morphology and structure of the sample were characterized by digital camera, scanning electron microscopy, and Fourier transform infrared spectroscopy spectra. By combining the advantages of high conductivity of graphene and high pseudocapacitance of PANI, the composite hydrogel was taken as supercapacitor electrode material. Cyclic voltammetry and galvanostatic charge/discharge experimental results show that the composite has excellent electrochemical performance. The specific capacitance value is 258.5 F g^?1 at a scan rate of 2 mV s^?1 and the specific capacitance value is up to 307 F g^?1 at a current density of 0.2 A g^?1. The specific capacitance value can still maintain 90 % of the initial value after repeating the galvanostatic charge–discharge for 1000 cycles at a current density of 1.0 A g^?1 showing good cycle stability.     

Fabrication and electrochemical capacitance of hierarchical graphene/polyaniline/carbon nanotube ternary composite film

A film composed of graphene (GN) sheets, polyaniline (PANI) and carbon nanotubes (CNTs) has been fabricated by reducing a graphite oxide (GO)/PANI/CNT precursor prepared by flow-directed assembly from a complex dispersion of GO and PANI/CNT, followed by reoxidation and redoping of the reduced PANI in the composite to restore the conducting PANI structure. Scanning electron microscope images indicate that the ternary composite film is a layered structure with coaxial PANI/CNT nanocables uniformly sandwiched between the GN sheets. Such novel hierarchical structure with high electrical conductivity perfectly facilitates contact between electrolyte ions and PANI for faradaic energy storage and efficiently utilizes the double-layer capacitance at the electrode–electrolyte interfaces. The specific capacitance of the GN/PANI/CNT estimated by galvanostatic charge/discharge measurement is 569 F g⁻¹ (or 188 F cm⁻³ for volumetric capacitance) at a current density of 0.1 A g⁻¹. In addition, the GN/PANI/CNT exhibits good rate capability (60% capacity retention at 10 A g⁻¹) and superior cycling stability (4% fade after 5000 continuous charge/discharge cycles).     

In situ synthesis of cabbage like polyaniline@hydroquinone nanocomposites and electrochemical capacitance investigations

A Cabbage like polyaniline@hydroquinone composite microsphere was synthesized using in situ polymerization and the electrochemical performance was investigated. The core template, p‐benzoquinone, is demonstrated working as an oxidizing agent for the in situ polymerization of PANI, and to be reduced to 1, 4‐hydroquinone after reaction. The morphology and microstructure of samples were examined by field emission scanning electron microscopy, transmission electron microscope, X‐ray photoelectron spectrometer, thermo gravimetric, and Fourier transform infrared spectra. The cyclic voltammetry, impedance and galvanostatic charge/discharge analysis demonstrates that PANI contributes electronic conductive channels for hydroquinone, and hydroquinone works as a pseudocapacitance component. The prepared PANI@hydroquinone nanocomposite exhibits brilliant electrochemical properties of a specific capacitance of 126.0 F g^?1 at a scan rate of 5 mV s^?1 and enhanced stability of about 85.1% of initial capacitance retained after 500 cycles scanning at a current density of 1 A g^?1. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42290.     

Electropolymerization and energy storage of poly[Ni(salphen)]/MWCNT composite materials for supercapacitors

Ni(salphen), a Schiff base ligand compound, was synthesized and electropolymerized on multiwalled carbon nanotube (MWCNT) electrodes in an acetonitrile solution via the pulse potentiostatic method and then applied as a supercapacitor electrode material. The polymerization mode was investigated through methyl replacement in the para‐position of phenyl rings in the Ni(salphen) monomer, and it was found that the Ni(salphen) monomers would polymerize by the generation of C? C bonds between the phenyl rings in the para‐position of the phenol moieties. The optimum condition for polymerization was evaluated, and when the polymerization time was 8 min, poly[Ni(salphen)] exhibited a specific capacitance up to 200 F g^?1 at a current density of 0.1 mA cm^?2, and the capacitance remains at 164 F g^?1 at 20 mA cm^?2. The energy density of the poly[Ni(salphen)] electrode reached 40 Wh kg^?1 at 0.1 mA cm^?2, about eight times greater than for a pure MWCNT electrode. Electrochemical performances were investigated, and the composites showed good redox property and ion transfer capability. This work showed that Ni(salphen) may be an attractive material in supercapacitors© 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44464.     

Benign enzymatic synthesis of multiwalled carbon nanotube composites uniformly coated with polypyrrole for supercapacitors

BACKGROUND: Recently, various composites of carbon nanomaterials and conducting polymers have been actively investigated as potential electrode materials for supercapacitors which can store and deliver large amounts of electrical energy promptly. Harsh chemical or complex electrodeposition methods have been studied to prepare such composites. In this report, the mild and simple enzymatic catalysis of horseradish peroxidase (EC 1.11.1.7) in aqueous solutions (pH 4.0) was utilized for the first time to prepare composites of multiwalled carbon nanotubes and polypyrrole. RESULTS: Electron micrographs show that in situ enzymatic reaction by horseradish peroxidase enables the uniform coating of multiwalled carbon nanotubes with polypyrrole without containing the polymer aggregates. The specific capacitance of the composites (46.2 F g^?1) measured with a two‐electrode cell containing an electrolyte of 1 mol L^?1 NaNO₃ increased more than four‐fold compared with that obtained with bare multiwalled carbon nanotubes (10.8 F g^?1). CONCLUSIONS: Horseradish peroxidase‐catalyzed in situ synthesis of the composites of multiwalled carbon nanotubes and polypyrrole requires neither the derivatization of multiwalled carbon nanotubes and/or pyrrole monomers nor the post‐doping of the synthesized composites to enhance the capacitance of the composites. © 2012 Society of Chemical Industry     

A highly oriented poly(3,4‐ethylenedioxythiophene) film: Facile synthesis and application for supercapacitor

A single crystal poly(3,4‐ethylenedioxythiophene) (PEDOT) film with highly oriented arrangement has been fabricated from an aqueous solution by a novel unipolar pulse electropolymerization method. Film formation mechanism was proposed based on the in situ mass change during electropolymerization process measured by the electrochemical quartz crystal microbalance. The compositions, morphology and crystal structure of the fabricated films are characterized by Fourier transfer infrared spectroscopy, scanning electron microscopy, and X‐ray diffraction, respectively. It is found that the prepared PEDOT film on carbon nanotubes (CNTs)‐modified electrode with a spongy dendritic structure possesses outstanding electroactivity, high specific capacitances (239.1 F?g^?1, including the specific capacitances of CNTs which is 21.4 F?g^?1), and excellent cycling stability with 7.3% decay from its initial capacitance over 10,000 cycles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43418.     

Dulse‐derived porous carbon–polyaniline nanocomposite electrode for high‐performance supercapacitors

Dulse‐derived porous carbon (DDPC)–polyaniline (PANI) nanocomposites were fabricated by a method based on the in situ chemical oxidation polymerization of aniline on DDPC. The characterization of the material showed that the nano‐PANI was grown on the surface of DDPC in the form of nanosticks or nanoparticles. The DDPC–PANI nanocomposites were further used as electrode materials for energy‐storage applications. Meanwhile, the effect of the amount of aniline on the electrochemical performance of DDPC–PANI was also investigated. The results show that a maximum specific capacitance of 458 F/g was achieved for the DDPC–PANI nanocomposites; this was higher than that of the DDPC electrode (218 F/g), and the PANI electrode (318 F/g). The specific capacitance of DDPC–PANI remained 66.0% of the initial value after 5000 cycles; this was higher than that of PANI (50.5%). Finally, a device of DDPC–PANI–activated carbon (AC) was assembled with DDPC–PANI as a positive electrode, which exhibited a high energy density of 9.02 W h/kg, which was higher than that of PANI–AC device. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45776.     

Influence of the reaction temperature on polyaniline morphology and evaluation of their performance as supercapacitor electrode

The polyaniline (PANI) nanostructures of tubular, spherical, and granules morphologies were synthesized by chemical oxidation approach in different reaction temperatures and used as the active electrode materials of symmetric redox supercapacitors. X‐ray diffraction and scanning electron microscopy techniques are employed for characterization of these PANIs. With the initial and reaction temperature increase, the morphology of PANI turned from block to spherical and tubular. Electrochemical properties of these PANI electrodes are studied by cyclic voltammetry (CV), agalvanostatic charge–discharge test, and electrochemical impedance spectroscopy (EIS) in 1M H₂SO₄ aqueous solution. The highest electrochemical properties are obtained on the PANI with tubular morphology. The initial specific capacitance of tubular, spherical, and granules PANI are about 300, 300, and 290 F g^?1 at a constant current of 5 mA. Meanwhile, the retention of the tubular PANI capacitance after 500 charge–discharge cycles was 75%, whereas the spherical and granules PANI was only 35% and 57%. The results indicate that tubular PANI electrodes have potential applications as high‐performance supercapacitors electrode materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3753–3758, 2013     

Electropolymerization of polyaniline on titanium oxide nanotubes for supercapacitor application

Vertically aligned polyaniline (PANI) nanotubes have great potential application in supercapacitor electrode material. In this paper we have investigated facile growth of PANI nanotubes on a titanium nanotube template (TNT) using electrochemical polymerization. The morphology of PANI nanostructures grown over TNT is strongly influenced by the scan rate in the electrochemical polymerization. The growth morphology of PANI nanotubes has been carefully analyzed by field emission scanning electron microscopy. The detailed growth mechanism of PANI nanotubes has been put forward. Specific capacitance value of 740 F g⁻¹ was obtained for PANI nanotube structures (measured at charge–discharge rate of 3 A g⁻¹).     

Fabrication of carbon nanotubes/polypyrrole/carbon nanotubes/melamine foam for supercapacitor

The carbon nanotubes (CNTs) have been loaded on the melamine foam (MF) to form the composite (CNTs/MF) by dip‐dry process, then polypyrrole (PPy) is coated on CNTs/MF (PPy/CNTs/MF) through chemical oxidation polymerization by using FeCl₃·6H₂O adsorbed on CNTs/MF as oxidant to polymerize the pyrrole vapor. Finally, CNTs are coated on the surface of PPy/CNTs/MF to increase the conductivity of the composite (CNTs/PPy/CNTs/MF) by dip‐dry process again. The composites have been characterized by X‐ray diffraction spectroscopy, scanning electron microscopy and electrochemical method. The results show that the structure of the composites has obvious influence on their capacitive properties. According to the galvanostatic charge/discharge test, the specific capacitance of CNTs/PPy/CNTs/MF is about 184 F g^?1 based on the total mass of the composite and 262 F g^?1 based on the mass of PPy (70.2 wt % in the composite) at the current density of 0.4 A g^?1, which is higher than that of PPy/CNTs/MF (120 F g^?1 based on the total mass of the composite and 167 F g^?1 based on the mass of the PPy). Furthermore, the capacitor assembled by CNTs/PPy/CNTs/MF shows excellent cyclic stability. The capacitance of the cell assembled by CNTs/PPy/CNTs/MF retains 96.3% over 450 scan cycles at scan rate of 20 mV s^?1, which is larger than that assembled by CNTs/PPy/MF (72.5%). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39779.     

3-Aminopropyltriethoxysilane-Assisted Si@SiO2/CNTs Hybrid Microspheres as Superior Anode Materials for Li-ion Batteries

A silicon based composite (Si@SiO₂/CNTs) with outstanding electrochemistry performance has been easily synthesized using a spray drying method; The composite microsphere is mainly made up of carbon nanotubes and the prepared nano silicon particles. With the help of a silane coupling agent, carbon nanotubes tightly intertwined with nano silicon particles and formed microspheres together. On the surface of the prepared nano silicon particles, a layer of oxide film plays a role as a barrier to reduce the rupture of the particles during the lithium intercalation/extraction process. In addition, the added twisted carbon nanotubes can help to maintain the conductive network, thus stabilizing the electrode working environment during the lithium intercalation/extraction process. As a superior anode material, an initial specific discharge capacity of approximately 2846.9 mAh g^?1 with a coulombic efficiency of 86 % and a reversible specific capacity of 2035.9 mAh g^?1 after 100 cycles at a constant density of 500 mA g^?1 are obtained.     

Laccase‐catalyzed synthesis of polypyrrole‐multiwalled carbon nanotube composites as energy storage materials for capacitors

Multiwalled carbon nanotubes (MWNTs) were coated with polypyrrole (PPy) using in situ enzymatic polymerization of pyrrole catalyzed by a laccase (benzenediol:oxygen oxidoreductase, EC 1.10.3.2) from Trametes versicolor. Transmission electron microscopy revealed that the MWNTs were uniformly coated with very thin layers of PPy without any indication of globular polymer aggregate formations. The enzymatic synthesis of the MWNTs/PPy composites was quite simple being performed in a one‐pot aqueous solution (pH 4.0) under mild reaction conditions. The potential of the composites with respect to the development of energy storage devices was demonstrated by fabricating a two‐electrode coin cell capacitor (diameter 20 mm, thickness 1.6 mm) utilizing the composites as electrode materials. The capacitance of the cell was 28.0 F g^?1 for the electrode material as measured by a galvanostatic charge–discharge method. The energy density and power density were 2.55 and 805 W kg^?1, respectively, which were close to those of the capacitors classified as ultracapacitors. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43307.     

Poly(2,6‐di(thiophene‐2‐yl)‐3,5bis(4‐(thiophene‐2‐yl)phenyl)dithieno [3,2‐b;2',3'‐d]thiophene)/carbon nanotube composite for capacitor applications

A novel monomer, 2,6‐di(thiophene‐2‐yl)‐3,5bis(4‐(thiophene‐2‐yl)phenyl)dithieno[3,2‐b;2',3'‐d]thiophene ( Th₄DTT) has been synthesized and used as an electro‐active material. It has been electropolymerized onto glassy carbon (GC) electrode in sodium dodecyl sulfate (SDS) solution (0.1 M) together with multi‐walled carbon nanotubes (MWCNT). A good capacitive characteristics for P(Th₄DTT)/MWCNT composite has been obtained by electrochemical impedance spectroscopy (EIS), which is, to our best knowledge, the first report on capacitor behavior of a dithienothiophene. A synergistic effect has been resolved by Nyquist, Bode‐magnitude—phase and admittance plots. Specific capacitance of the conducting polymer/MWCNT, calculated from cyclic voltammogram (CV) together with area and charge formulas, has been found to be 20.17 F g^?1. Long‐term stability of the capacitor has also been tested by CV, and the results indicated that, after 500 cycles, the specific capacitance is 87.37% of the initial capacitance. An equivalent circuit model of R_s(C₁(R₁(Q(R₂W))))(C₂R₃) has been obtained to fit the experimental and theoretical data. The double layer capacitance (C_dl) value of P(Th₄DTT)/MWCNT (4.43 mF cm^?2) has been found to be 25 times higher than P(Th₄DTT) (C_dl= 0.18 mF cm^?2). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40061.     

Electrocatalysis and detection of nitrite on a polyaniline‐Cu nanocomposite‐modified glassy carbon electrode

A polyaniline (PANI)‐Cu nanocomposite‐modified electrode was fabricated by the electrochemical polymerization of aniline and the electrodeposition of copper under constant potentials on a glassy carbon electrode (GCE), respectively. Scanning electron microscope result shows that the PANI‐Cu composite on the surface of the GCE displays the nanofibers having an average diameter of about 80 nm with lengths varying from 1.1 to 1.2 μm. The electrode exhibits enhanced electrocatalytic behavior to the reduction of nitrite compared to the PANI‐modified GCE. The effects of applied potential, pH value of the detection solution, electropolymerization charge, temperature, and nitrite concentration on the current response of the composite‐modified GCE were investigated and discussed. Under optimal conditions, the PANI‐Cu composite‐modified GCE can be used to determine nitrite concentration in a wide linear range (n = 18) of 0.049 and 70.0 μM and a limit of detection of 0.025 μM. The sensitivity of the electrode was 0.312 μA μM^?1 cm^?2. The PANI‐Cu composite‐modified GCE had the good storage stability. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and electrochemical properties of graphene oxide/nanosulfur/polypyrrole ternary nanocomposite hydrogel for supercapacitors

A method for synthesizing Graphene oxide (GO)/nano‐sulfur/polypyrrole (PPy) ternary nanocomposite hydrogel is depicted. The higher surface area of GO, PPy porous structure and their excellent conductivity are utilized, and the GO hydrogel can be made easily. The products are characterized by field‐emission scanning electron microscopy (FESEM), X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, and electrochemical workstation. The results demonstrated that GO/nano‐S/PPy ternary nanocomposite hydrogel is successfully synthesized. The electrochemical properties are investigated by cyclic voltammetry, galvanostatic charge/discharge measurements, and cycling life in a three‐electrode system in 1M Li₂SO₄ electrolyte solution. The GO/nano‐S/PPy ternary nanocomposite hydrogel exhibit a high specific capacitance of 892.5 F g^?1 at scan rates of 5 mV s^?1 and the capacitance retain about 81.2% (594.8 F g^?1) of initial capacitance (732.5 F g^?1) after 500 cycles at a current density of 1 A g^?1. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40814.