Fabrication of Tiron‐doped polypyrrole/MWCNT composite electrodes with high mass loading and enhanced performance for supercapacitors

In this study, the aromatic sulfonate compound Tiron with high charge to mass ratio is used as an anionic dopant for synthesis of polypyrrole (PPy). The fabricated PPy is investigated for electrochemical supercapacitor (ES) application. Testing results show that Tiron allows reduced PPy agglomeration, smaller particle size and improved charge storage properties of PPy. High capacitance and improved capacitive retention at high scan rates are achieved by the fabrication of PPy/multiwalled carbon nanotube (MWCNT) composite electrode using safranin (SAF) as a co‐dispersant. The Tiron‐doped PPy electrode shows the highest capacitance of 7.8 F cm^?2 with a mass of 27 mg cm^?2. The Tiron‐doped PPy/MWCNT composite electrode shows good capacitance retention with a capacitance of 1.0 F cm^?2 at the scan rate of 100 mV s^?1. Symmetric supercapacitor cells are fabricated using PPy based active materials. An energy density of 0.36 mWh cm^?2 is achieved. The energy/power density and capacitance retention of the Tiron‐doped PPy/MWCNT ES is significantly improved in comparison with PPy‐based ES, prepared without Tiron or MWCNT. The Tiron‐doped PPy/MWCNT symmetric supercapacitor presents good cycling performance with 91.4% capacitance retention after 1000 charge–discharge cycles. The PPy/MWCNT composites, prepared using Tiron and SAF co‐dispersant, are promising electrodes for ES. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42376.     

Fabrication of polypyrrole (PPy)/carbon nanotube (CNT) composite electrode on ceramic fabric for supercapacitor applications

Polypyrrole (PPy)/carbon nanotube (CNT) composite electrodes are fabricated on ceramic fabrics for electrochemical capacitor applications. The CNTs are grown on the ceramic fabrics by the chemical vapor deposition (CVD) method and PPy is subsequently coated on them by chemical polymerization. The large surface area and high conductivity of the CNTs on the porous ceramic fabrics enhance their energy storage capacity. PPy provides not only additional capacitance as an active material, but also enhances the adhesion between the CNTs and ceramic fabrics. Furthermore, PPy acts as a conducting binder for connecting every individual CNT to increase the capacitance. The morphology of the PPy–CNTs on the ceramic fabrics is confirmed by SEM and TEM, and the electrochemical characteristics are investigated by cyclic voltammetry and galvanostatic charge–discharge tests.     

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.     

Carbon nanotube/graphene composite for enhanced capacitive deionization performance

In this study, single-walled carbon nanotubes were combined with graphene oxide nanosheets in aqueous dispersion and then chemically reduced to form the carbon nanotube/graphene (CNT/G) composite as electrodes for capacitive deionization (CDI). The structure of the CNT/G composite was highly porous, with single-walled carbon nanotubes (SWCNTs) sandwiched between graphene sheets that functioned as spacers and provided diffusion paths for smooth and rapid ion conduction. The associated increase in the electrical double-layer capacitance enhanced capacitive deionization performance. The CNT/G composite achieved a specific capacitance of 220 F/g and an electrosorption capacity of 26.42 mg/g with 100% regeneration, showing great potential as a high performance electrode material in CDI applications.     

Preparation and electrochemistry of nanostructured PPy/graphite nanosheets/rare earth ions composites for supercapacitor

Highly conductive PPy/graphite nanosheets/rare earth ions (PPy/nanoG/RE³⁺) composites were prepared via in‐situ polymerization with p‐toluenesulfonic acid as a dopant and FeCl₃ as an oxidant. The microstructures of nanoG and PPy/nanoG/RE³⁺ were characterized by the SEM and TEM examinations. It was found that nanoG and PPy nanospheres formed the uniform composite with the PPy nanospheres embedded on the nanoG surface and/or filled between the nanoG. The effects of nanoG and RE³⁺ on the electrical conductivity and electrochemical performance of the composites were investigated. The results showed that the nanoG and RE³⁺ as the filler had effect on the conductivity and electrochemical performance of PPy/nanoG/RE³⁺ composites, which played an important role in forming a conducting network in PPy matrix. A specific capacitance of as high as 175 F/g at a current density of 1 A/g was achieved over the PPy/nanoG/Gd³⁺ composite. The capacitance of the PPy/nanoG/Gd³⁺ composite decreased only 5.1% after 800 charging/discharging cycles at a current density of 1 A/g. POLYM. ENG. SCI., 54:2731–2738, 2014. © 2013 Society of Plastics Engineers     

Preparation and enhanced electrochemical properties of Ag/polypyrrole composites electrode materials

Ag/polypyrrole (PPy) composites were synthesized with different dispersants via interface polymerization method. The morphology of the composites was investigated by scanning electron microscopy and transmission electron microscopy, and the results showed that the dispersant had strong effect on the morphology of the obtained composites. The structure of the products was characterized by Fourier transform infrared spectroscopy, and X‐ray diffraction. The specific capacitance and impedence of Ag/PPy composites electrode was evaluated through charge/discharge measurements and electrochemical impedance spectroscopy, respectively. Electrochemical performances indicated that Ag/PPy composite electrode used polyvinyl alcohol as dispersant exhibited the highest specific capacitance of 635.5 F/g at a current density of 2.45 mA/g, which provided potential application as supercapacitor materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of the flexible polypyrrole/polypropylene composite fibrous film for electrochemical capacitor

Polypyrrole (PPy)/polypropylene fibrous membrane (PPF) composite materials with different PPy contents are prepared through in situ chemical oxidation polymerization in the pyrrole atmosphere at room temperature by dissolving the FeCl₃·6H₂O in methanol and acetonitrile as oxidant. The morphology of the composite is examined by scanning electron microscope (SEM), the conductivities of the composites are measured by convenient four‐probe method, and the properties of the capacitor cells assembled by the obtained PPy/PPF are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS) measurements. The results show that the morphology, conductivity, and the capacitor property of the composite are influenced strongly by the solvent of the oxidant. The capacitor assembled by the PPy/PPF prepared by using acetonitrile as the solvent for FeCl₃^.6H₂O can adapt for quick charge/discharge, and exhibit the highest capacitance of about 72.5 F g^?1 when the PPy content is about 8.0%. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Interfacial synthesis of polypyrrole/graphene composites and investigation of their optical,electrical and electrochemical properties

We report the development of a novel route for the synthesis of polypyrrole/graphene (PPy/GR) composites by liquid ? liquid interfacial polymerization, where GR and the initiator were dispersed in the aqueous phase and the monomer was dissolved in the organic phase. The synthesized samples were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, ultraviolet–visible spectroscopy, Raman spectroscopy, X‐ray diffraction, thermogravimetric analysis, electrochemical and electrical conductivity measurements. Structural analysis reveals a uniform dispersion of GR sheets in the PPy matrix. The composites showed noticeable improvement in thermal stability and electrical conductivity (8.45 S cm^?1) and excellent electrochemical reversibility in comparison with pure PPy. A specific capacitance of 260 F g^?1 at a current density of 100 mA g^?1 was achieved for the composite during the charge–discharge process. © 2013 Society of Chemical Industry     

Determination of the specific capacitance of conducting polymer/nanotubes composite electrodes using different cell configurations

Composite materials containing 20 wt.% of multiwalled carbon nanotubes (MWNTs) and 80 wt.% of chemically formed conducting polymers (ECP) as polyaniline (PANI) and polypyrrole (PPy) have been prepared and used for supercapacitor electrodes. The well conducting properties of MWNTs and their available mesoporosity allow a good charge propagation in the composites. Moreover, due to the good resiliency of MWNTs, an excellent stability of the supercapacitor electrodes is observed. It has been shown that the capacitance values for the composites strongly depend on the cell construction. In the case of three electrode cells, extremely high values can be found from 250 to 1100 F/g, however in the two electrode cell much smaller specific capacitance values of 190 F/g for PPy/MWNTs and 360 F/g for PANI/MWNTs have been measured. It highlights the fact that only two-electrode cells allow a good estimation of materials performance in electrochemical capacitors. The applied voltage was found to be the key factor influencing the specific capacitance of nanocomposites. For operating each electrode in its optimal potential range, asymmetric capacitors have been built with PPy/MWNTs as negative and PANI/MWNTs as positive electrodes giving capacitance values of 320 F/g per electrode material.     

Electroactive and temperature‐sensitive hydrogel composites

The composites of the polypyrrole (PPy) and polyelectrolyte copolymers (PE) were prepared by electrochemical polymerization. The various compositions of the polyelectrolyte copolymers were used as a dopant, and were composed of copolymers of water‐soluble polymers and 2‐Acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS). Thermally sensitive (N‐isopropyl acrylamide, NiPAAm) and insensitive (acrylamide, AAm) polymers were used as the water‐soluble polymer. The electrochemical activity and mass change during the redox process of the PPy composites were investigated by potentiodynamic voltametry and electrochemical quartz crystal microbalance (EQCM). The mass change during the redox process was mainly concerned with the cation in the electrolyte solution. When the electrochemical activity of the PPy was larger than the amount of the polyelectrolyte anion (AMPS), the insertion/expulsion of the monoanion (ClO) into/from the PPy composite also occurred to ionically bond with the PPy in the redox process. The PPy/P(NiPAAm/AMPS) shows a significant mass decrease with increasing the temperature compared with the PPy/P(AAm/AMPS). The transition temperature of the PPy/P(NiPAAm/AMPS) is higher in the oxidized state than in the reduced state. The transition temperature of PPy composite increases with the composition of the hydrophilic electrolyte (AMPS). © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 311–321, 1999     

Defect engineering on the defluorinated MWCNTs@SnO2@N-doped carbon composite for enhanced lithium storage performance

When tin oxide (SnO₂) is used in the anode of lithium-ion batteries, its capacity decreases dramatically due to poor conductivity and volume effects during the electrochemical cycle. Although composites with traditional carbon-based materials can improve this shortcoming, the low capacitance of such materials still limits the capacity of the composites. Therefore, we applied defect engineering to SnO₂/C composite electrodes for the first time, and prepared D-MWCNTs@SnO₂@N–C composite electrodes with hollow rod structures. Defects were constructed in the carbon materials to promote electron diffusion and ion storage active sites. The hollow structure can adapt to the volume change that occurs during Li-ion insertion/desorption. In addition, the detachment of F atoms and the insertion of N atoms, which are chemical processes that occur on the surface of carbon materials, promote an increase in surface porosity and defect density, thereby providing additional lithium storage sites. The double carbon effect caused by defect engineering provides a multidimensional transport path and rapid migration rate for Li-ions, which enables the electrode to display excellent electrochemical performance; thus, this work could lead to the preparation of next-generation anode materials with high energy storage capacity, high rate capability and high cycle stability.     

Composite sodium p‐toluene sulfonate–polypyrrole–iron anode for a lithium‐ion battery

In this study, p‐toluene sulfonate (TsONa) doped polypyrrole (PPy) was synthesized for an anode in a lithium‐ion battery via a one‐step facile electropolymerization on Fe foil. The obtained TsONa–PPy–Fe composite electrode was investigated with scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy, and galvanostatic charge–discharge profiling. As expected, many irregular microspherical particles of TsONa‐doped PPy formed and combined tightly with the surface of Fe foil. Furthermore, the obtained TsONa–PPy–Fe anode also delivered satisfactory electrochemical performances. For example, the reversible capacity was still about 105–115 mAh/g, even after at least 50 cycles. The high lithium storage activity of PPy and the high conductivity of the TsONa‐doped PPy jointly contributed into the satisfactory electrochemical performances. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44935.     

Flexible electrodes based on polypyrrole/manganese dioxide/polypropylene fibrous membrane composite for supercapacitor

The composites of polypyrrole/manganese dioxide/polypropylene fibrous films (PPy/MnO₂/PPF) have been prepared in situ through chemical oxidation polymerization by using the mixture of FeCl₃·6H₂O and MnO₂ adsorbed on PPF as oxidant in the atmosphere of pyrrole vapor at room temperature. The morphologies and structures of the composites are investigated by using scanning electron microscope and X-ray diffraction spectroscopy. The properties of the capacitor cells assembled by the composites of PPy/MnO₂/PPF are evaluated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy methods. The results reveal that the morphologies, conductivities and capacitance performance of the composites are influenced strongly by the content of MnO₂ in the solution of oxidant. The capacitors assembled by PPy/MnO₂/PPF exhibit the property of quick charge/discharge, and the highest specific capacitance of about 110 F g⁻¹ is obtained when the PPy/MnO₂ content in the composite is about 17.4%.     

Conversion of pencil graphite to graphene/polypyrrole nanofiber composite electrodes and its doping effect on the supercapacitive properties

Graphene platelets were synthesized from pencil flake graphite and commercial graphite by chemical method. The chemical method involved modified Hummer's method to synthesize graphene oxide (GO) and the use of hydrazine monohydrate to reduce GO to reduced graphene oxide (rGO). rGO were further reduced using rapid microwave treatment in presence of little amount of hydrazine monohydrate to graphene platelets. Chemically modified graphene/polypyrrole (PPy) nanofiber composites were prepared by in situ anodic electropolymerization of pyrrole monomer in the presence of graphene on stainless steel substrate. The morphology, composition, and electronic structure of the composites together with PPy fibers, graphene oxide (GO), rGO, and graphene were characterized using X‐ray diffraction (XRD), laser‐Raman, and scanning electron microscopic (SEM) methods. From SEM, it was observed that chemically modified graphene formed as a uniform nanocomposite with the PPy fibers absorbed on the graphene surface and/or filled between the graphene sheets. Such uniform structure together with the observed high conductivities afforded high specific capacitance and good cycling stability during the charge–discharge process when used as supercapacitor electrodes. A specific capacitance of supercapacitor was as high as 304 F g^?1 at a current density of 2 mA cm^?1 was achieved over a PPy‐doped graphene composite. POLYM. ENG. SCI., 55:2118–2126, 2015. © 2014 Society of Plastics Engineers     

Synthesis,characterization and supercapacitors of electrically conductive PPy/graphene/rare earth ions composites

PPy/graphene/rare earth ions (PPy/GR/RE³⁺) were prepared using an in situ chemical polymerization of the monomer in the presence of FeCl₃ oxidant and p-toluenesulfonic acid dopant. The PPy/GR/RE³⁺ composites were characterized by FT-IR spectroscopy, four-point probe conductivity, scanning electron microscopy and transmission electron microscopy. The maximum conductivity of PPy/GR/Gd³⁺ composites is about 9.71 S/cm found with 1 wt% GR and 2 wt% Gd³⁺ at room temperature. The capacitance of the composite electrodes was investigated with cyclic voltammetry. As results of this study, the PPy/GR/Gd³⁺ was effective to obtain fully reversible and very fast faradaic reaction. Hence, the PPy/GR/Gd³⁺ could contribute to the pseudo-capacitive charge storage. The PPy/GR/Gd³⁺ exhibited higher specific capacitance of ~238 F/g at 1 A/g current density. Thermal gravimetric analysis demonstrates an improved thermal stability of PPy in the PPy/GR/Gd³⁺ composites.     

Atomic layer deposition of TiO2 on carbon-nanotubes membrane for capacitive deionization removal of chromium from water

Chromium (Cr) is a common heavy metal that has severe impacts on the ecosystem and human health. Capacitive deionization (CDI) is an environment-friendly and energy-efficient electrochemical purification technology to remove Cr from polluted water. The performance of CDI systems relies primarily on the properties of electrodes. Carbon-nanotubes (CNTs) membranes are promising candidates in creating advanced CDI electrodes and processes. However, the low electrosorption capacity and high hydrophobicity of CNTs greatly impede their applications in water systems. In this study, we employ atomic layer deposition (ALD) to deposit TiO₂ nanoparticulates on CNTs membranes for preparing electrodes with hydrophilicity. The TiO₂-deposited CNTs membranes display preferable electrosorption performance and reusability in CDI processes after only 20 ALD cycles deposition. The total Cr and Cr(VI) removal efficiencies are significantly improved to 92.1% and 93.3%, respectively. This work demonstrates that ALD is a highly controllable and simple method to produce advanced CDI electrodes, and broadens the application of metal oxide/carbon composites in the electrochemical processes.     

Supercapacitive properties of electrodeposited polypyrrole on acrylonitrile–butadiene rubber as a flexible current collector

Flexible sheets consisting of acrylonitrile–butadiene rubber (NBR) and vapor-grown carbon fiber (VGCF) are newly prepared varying the composition (VGCF 10–30 wt%) for use as a current collector of supercapacitor electrodes. The electrical conductivity of as-prepared VGCF/NBR current collector can be enhanced as the content of VGCF increases. The VGCF/NBR current collector is then electrodeposited with pyrrole using a potentiodynamic cyclic voltammetry to yield a polypyrrole (PPy)/VGCF/NBR composite electrode. Cyclic voltammetry result for the PPy/VGCF/NBR composites shows that the sample with 30 wt% VGCF achieves a maximum specific capacitance (125.8 F g^?1) at 5?mV?s^?1 and reaches a lower specific capacitance at higher scan rates. In addition, the flexibility of supercapacitor electrode of PPy can also be established with a comparable capacitance value by using the NBR-based current collector.     

Preparation and electrochemical properties of polyaniline/α‐RuCl3.xH2O composites for supercapacitor

Polyaniline/α‐RuCl₃.xH₂O composites were successfully synthesized by an in‐situ chemical polymerization and employed as new electrode materials in supercapacitors. The synthesized composites were characterized physically by scanning electronic microscope (SEM). The electrochemical capacitance performance of these composites was investigated by cyclic voltammetry, galvanostatic charge–discharge tests and AC impedance spectroscopy with a three‐electrode system in 1 mol l⁻¹ NaNO₃ aqueous solution electrolyte. The polyaniline/α‐RuCl₃.xH₂O composites electrodes showed much higher specific capacitance, better power characteristics and were more promising for application in capacitor than pure polyaniline electrode. The effect and role of α‐RuCl₃.xH₂O in the composite electrode were also discussed in detail. POLYM. COMPOS., 34:2142–2147, 2013. © 2013 Society of Plastics Engineers     

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.     

Preparation and characterization of polypyrrole/modified multiwalled carbon nanotube nanocomposites polymerized in situ in the presence of barium titanate

Polypyrrole (PPy) composites were prepared with both unmodified and amine‐modified multiwalled carbon nanotubes (MWCNTs) in the presence and absence of barium titanate (BaTiO₃) by in situ oxidative polymerization. A uniform coating of PPy on the MWCNTs and BaTiO₃ surfaces was confirmed by field emission scanning electron microscopy and high‐resolution transmission electron microscopy images. The structure of the pure and amine‐modified MWCNTs were identified by Fourier transform infrared spectroscopy. The incorporation of BaTiO₃ enhanced the thermal stability and capacitance properties of the composites. The maximum specific capacitance and energy density values found for the PPy/amine‐modified MWCNT/BaTiO₃ composites were 155.5 F/g and 21.6 W h/kg, respectively, at a scan rate of 10 mV/s. The maximum power density was found to be 385.7 W/kg for the same composite at a scan rate of 200 mV/s. Furthermore, the impedance spectra of the composites showed moderate capacitive behavior. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013