Polyaniline Electrode Research Articles

Facile synthesis of nanostructured polyaniline in ionic liquids for high solubility and enhanced electrochemical properties

As one of the most investigated conducting polymers, polyaniline (PANI) is considered to be of practical use in many applications. In this study, two new ionic liquids, 1-methylimidazolium hydrogen sulfate ([Hmim]HSO4) and 1-methyl-3-n-butylimidazopersulfate ([C4mim]2S2O8), which were synthesized from 1-methylimidazole ([Hmim]), were used as solvent and dopant, oxidizer, respectively, for in situ polymerization of aniline. Because of the application of the unique structure of ionic liquid, we obtained the ionic liquid–doped polyaniline (IL-PANI) with high solubility (25 mg mL−1 in dimethyl sulfoxide (DMSO)). And by adjusting the ratio of [C4mim]2S2O8 to aniline monomer, the preferred PANI nanofibers could be controlled to form a three-dimensional porous structure. It was found that the ion/electron transport channels could be formed inside the 3D structure. Thus, the redox reactions could occur both at the surface and inside the PANI electrode. Electrochemical characterization showed that the fabricated PANI electrode exhibited a specific capacitance of 489 F g−1 at a current density of 0.5 A g−1. Also, the capacity retention rate reached up to 81% after 4000 cycles investigated at 2 A g−1. In addition, a high-energy density of 80.2 Wh kg−1 was measured when [Hmim]HSO4 was used as an electrolyte. Thus, the present work suggested a new strategy for fabricating high-performance PANI electrode for supercapacitor applications.

A simple strategy to prepare polyaniline nanorods by surfactant-assisted electropolymerization for remarkably improved supercapacitive performances

Abstract This work reports on the significant improvement of electrochemical capacitive properties of the polyaniline (PANI) electrode via morphology changes, following an efficient and simple route. Specifically, a surfactant-assisted electropolymerization method is put forward to prepare PANI nanorods (PNRs) electrode and the formation mechanism of PNRs is investigated. In comparison to PANI electrode with compact microstructures, PNRs electrode has a dispersed nanorod-shaped morphology, showing substantially improved supercapacitive performances. The resulting PNRs electrode has the high areal capacitance of 345.9 mF cm−2, which represents a boost of as much as 40% comparing with that of PANI electrode. The PNRs electrode also features superior rate performance and excellent cycling stability, exhibiting 93.1% of capacitance retention after 10000 cycles. The present study has demonstrated a new and simple strategy to prepare nanostructured PANI and the prepared PNRs supercapacitor electrode is very promising for practical applications.

High electrochemical performance of supercapacitor electrode with para-aminophenyl graphene/polyaniline cross-linking nanocomposites

The purpose of this study is to report an effective approach to improve the electrochemical performance of polyaniline electrode by fabricating para-aminophenyl graphene/polyaniline cross-linking nanocomposites (PAG/PANI). The chemical graft between PAG and PANI, and the electrostatic incorporation between PANI inter-chains could provide the stable structural foundation for the improvement of cyclic stability. HCl and 1,5-naphthalene sulfonic acid (NSA) were both used as dopants to guarantee high doping level of PANI. The PAG/PANI electrode had a high specific capacitance of 1092.3 F g−1 at 5 mV s−1, and also showed a high cyclic stability after 3000 cycles. These results indicated that the PAG/PANI electrode would have a broad application prospect in energy storage device.

Graphene Oxide Decorated Nanometal-Poly(Anilino-Dodecylbenzene Sulfonic Acid) for Application in High Performance Supercapacitors.

Graphene oxide (GO) decorated with silver (Ag), copper (Cu) or platinum (Pt) nanoparticles that are anchored on dodecylbenzene sulfonic acid (DBSA)-doped polyaniline (PANI) were prepared by a simple one-step method and applied as novel materials for high performance supercapacitors. High-resolution transmission electron microscopy (HRTEM) and high-resolution scanning electron microscopy (HRSEM) analyses revealed that a metal-decorated polymer matrix is embedded within the GO sheet. This caused the M/DBSA–PANI (M = Ag, Cu or Pt) particles to adsorb on the surface of the GO sheets, appearing as aggregated dark regions in the HRSEM images. The Fourier transform infrared (FTIR) spectroscopy studies revealed that GO was successfully produced and decorated with Ag, Cu or Pt nanoparticles anchored on DBSA–PANI. This was confirmed by the appearance of the GO signature epoxy C–O vibration band at 1040 cm−1 (which decreased upon the introduction of metal nanoparticle) and the PANI characteristic N–H stretching vibration band at 3144 cm−1 present only in the GO/M/DBSA–PANI systems. The composites were tested for their suitability as supercapacitor materials; and specific capacitance values of 206.4, 192.8 and 227.2 F·g−1 were determined for GO/Ag/DBSA–PANI, GO/Cu/DBSA–PANI and GO/Pt/DBSA–PANI, respectively. The GO/Pt/DBSA–PANI electrode exhibited the best specific capacitance value of the three electrodes and also had twice the specific capacitance value reported for Graphene/MnO2//ACN (113.5 F·g−1). This makes GO/Pt/DBSA–PANI a very promising organic supercapacitor material.

Decoupling half-reactions of electrolytic water splitting by integrating a polyaniline electrode

A low-cost conducting polymer material polyaniline is developed as a solid-state redox mediator for decoupling the two half-reactions of water splitting in acidic media.

PANINFs synthesized electrochemically as an electrode material for energy storage application

To obtain the highest performance of supercapacitive properties, it is necessary to discover an appropriate pair of electrode material and electrolyte. Supercapacitors have many applications in the industry over batteries, and our result shows the advantages of low-cost polyaniline (PANI) electrode material in supercapacitors. In the present work, the polyaniline nanofibers (PANINFs) thin films can be directly used as an electrode for supercapacitor. PANINFs electrode showed maximum specific capacitance of 633 F/g which exhibited at 5 mV/s scan rate, the specific energy density of 45.67 Wh/kg, the power density of 500 W/kg and the coulomb efficiency of 85.59% at 0.5 mA/cm2 current density with 0.32 Ω equivalent series resistance (ESR) value. The capacitance value is obtained by electrochemical impedance spectroscopy (EIS) of 20.33 mF/cm2 with the relaxation time of 0.14 s. Nanofibrous network (50–60 nm diameter) confirmed hydrophilic nature by wettability test. From the supercapacitive performance of PANINFs thin films conclude that they are promising for energy storage application.

Piezoelectric-Driven Self-Powered Patterned Electrochromic Supercapacitor for Human Motion Energy Harvesting

The rapid development of a self-powered system (SPS) has aroused an increasing interest in the field of wearable electronics. The current development trend in wearable electronics is toward integration, portability, miniaturization, and sustainability. Hence, a wearable piezoelectric-driven self-powered patterned electrochromic supercapacitor (ESC) is presented here, which is integrated with the energy harvesting, conversion, storage and indication technologies. The patterned polyaniline (PANI) electrodes electrodeposited by coupling cyclic voltammetric and galvanostatic (CV-GS) techniques were assembled as patterned ESC, which served to store the energy and indicate the charging/discharging status simultaneously. With the advantages of flexibility and biocompatibility, the polyvinylidene difluoride (PVDF) nanofibers were fabricated by electrospinning to establish the piezoelectric nanogenerators (PENGs) as the energy-harvesting device, which can be attached to human body to harvest mechanical kinetic ene...

A Long‐Cycle‐Life Self‐Doped Polyaniline Cathode for Rechargeable Aqueous Zinc Batteries

AbstractRechargeable aqueous zinc batteries are promising energy‐storage systems for grid applications. Highly conductive polyaniline (PANI) is a potential cathode, but it tends to deactivate in electrolytes with low acidity (i.e. pH >1) owing to deprotonation of the polymer. In this study, we synthesized a sulfo‐self‐doped PANI electrode by a facile electrochemical copolymerization process. The −SO3− self‐dopant functions as an internal proton reservoir to ensure a highly acidic local environment and facilitate the redox process in the weakly acidic ZnSO4 electrolyte. In a full zinc cell, the self‐doped PANI cathode provided a high capacity of 180 mAh g−1, excellent rate performance of 70 % capacity retention with a 50‐fold current‐density increase, and a long cycle life of over 2000 cycles with coulombic efficiency close to 100 %. Our study opens a door for the use of conducting polymers as cathode materials for high‐performance rechargeable zinc batteries.

A Long-Cycle-Life Self-Doped Polyaniline Cathode for Rechargeable Aqueous Zinc Batteries.

Rechargeable aqueous zinc batteries are promising energy-storage systems for grid applications. Highly conductive polyaniline (PANI) is a potential cathode, but it tends to deactivate in electrolytes with low acidity (i.e. pH >1) owing to deprotonation of the polymer. In this study, we synthesized a sulfo-self-doped PANI electrode by a facile electrochemical copolymerization process. The -SO3 - self-dopant functions as an internal proton reservoir to ensure a highly acidic local environment and facilitate the redox process in the weakly acidic ZnSO4 electrolyte. In a full zinc cell, the self-doped PANI cathode provided a high capacity of 180 mAh g-1 , excellent rate performance of 70 % capacity retention with a 50-fold current-density increase, and a long cycle life of over 2000 cycles with coulombic efficiency close to 100 %. Our study opens a door for the use of conducting polymers as cathode materials for high-performance rechargeable zinc batteries.

Application of Natural Plant Sensitizers with Polyaniline Electrode Couple in Dye-Sensitized Solar Cells

Application of Natural Plant Sensitizers with Polyaniline Electrode Couple in Dye-Sensitized Solar Cells

Hierarchical porous polyaniline supercapacitor electrode from polyaniline/silica self‐ aggregates

AbstractTo lengthen the lifecycles of polyaniline (PANI) electrodes, a hierarchical porous PANI was synthesized from PANI/silica self‐aggregates through a facile one‐pot method. Hydrogen bonding between NH groups in aniline/PANI and OH groups in nanosilica template led to a type of self‐assembly, which enabled the formation of uniform nanoparticles. Silica self‐aggregates provided macroporous channels, resulting in a decreased diffusion distance. After removal of the hard template, the porous PANI had a large, porous surface area (55.89 m2 g−1), in comparison with nonporous PANI (12.45 m2 g−1). The porous PANI was analyzed using Fourier transform infrared and UV‐visible spectroscopies, scanning electron microscopy, thermogravimetric analysis, cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge–discharge measurements. Because of its hierarchical structure, the resultant porous PANI possessed a higher capacitance (397 F g−1) than nonporous PANI (280 F g−1) at 1 A g−1 in 1 mol L−1 H2SO4 electrolyte. © 2018 Society of Chemical Industry

Remarkably enhanced performances of polyaniline/electrochemically surface-treated graphite electrodes with optimal charge transfer pathways for flexible supercapacitor application

We propose a strategy to enhance the electrochemical performances of electrodes by optimizing charge transfer pathways at the current collector/electroactive material interface. A facile method is developed for electrochemical surface treatment of graphite, and the obtained electrochemical surface-treated graphite is utilized as substrate for electropolymerization of polyaniline, which facilitates the construction of high-quality electrical links at the interface of polyaniline and electrochemical surface-treated graphite. Effect of galvanostatic and potentiostatic polymerization on electrochemical properties of polyaniline electrodes is also examined. Electrochemical measurements indicate that the potentiostatically polymerized polyaniline electrode has superior supercapacitive performances. In particular, polyaniline/electrochemical surface-treated graphite electrode exhibits remarkably enhanced electrochemical properties in comparison with polyaniline/graphite electrode, which can be ascribed to the optimized charge transfer pathways at current collector/electroactive material interface for the former. Polyaniline/electrochemical surface-treated graphite electrode achieves a high specific capacitance of 437.9 mF cm−2 at 0.5 mA cm−2. Moreover, the polyaniline/electrochemical surface-treated graphite electrodes are used to assemble a flexible solid-state supercapacitor. The device demonstrates high flexibility, superior supercapacitive performances, and good cycling stability, which holds great promise for use in flexible electronics.

Preparation and characterization of Grafoil/Ni and polyaniline/Ni composites from the controlled electrochemical reduction of NiCl42-

The controlled reduction of a nickel metal anion, NiCl42−, at a carbon (Grafoil) and Polyaniline (PANI) electrode is explored. The incremental increase of Ni deposits is achieved from the reduction of the metal precursor at both electrodes. The normal oxidation/reduction was used to facilitate the uptake and dispersion of the precursor using electrostatic interactions with the positively charged PANI. The controlled in-situ reduction of the dispersed Ni precursor in the polymer was utilized to produce PANI/Ni composites with variable metal content. Scanning electron microscope (SEM) analysis and energy dispersive x-ray (EDX) spectroscopy of both substrates confirm the reduction of the Ni metal precursor at both electrodes. The chemical reactivity of the Ni metal deposited was also confirmed for both substrates using surface specific electrochemical reactions including the formation/reduction of oxidized nickel species and the catalytic oxidation of methanol in alkaline solutions (pH ≈ 14). The electrochemistry associated with NiOOH/Ni(OH)2 and the catalytic oxidation of methanol is resolved in alkaline solution for both electrodes. Furthermore, the electrochemical activity of PANI/Ni composite materials is maintained without acid doping the polymer. Finally, an alternative pathway for the inclusion of anionic transition metal species in PANI that eliminates the competitive uptake of proton and metal cation precursors commonly used in traditional acidic environments is demonstrated.

Enhancement in supercapacitive performances of polyaniline nanofiber electrodes using surface-expanded graphite substrate

A facile surface-treated method is developed to fabricate surface-expanded graphite foil (SE-GF), which serves as substrate for the electrochemical growth of polyaniline (PANI), to enhance the supercapacitive performances of obtained PANI electrodes. We also compare the electrochemical properties of electro polymerized PANI with different dopants. Comparing with H2SO4 doped PANI electrodes, HClO4 doped PANI electrodes show enhanced electrochemical capacitive properties due to the formed loose morphology of nanofibers. More importantly, the supercapacitive performances of PANI nanofibers grown on SE-GF substrate are remarkably improved in comparison to those grown on GF substrate. This is caused by the optimal electron transfer pathways constructed at the interface of SE-GF substrate and PANI films. The resulting SE-GF/PANI electrodes exhibit superior electrochemical properties such as high specific capacitance (422.1 mF cm−2 at 0.5 mA cm−2), good rate performance, and remarkable cycling stability (94.1% of capacitance retention for 5000 cycles). Such characteristics offer great promise in high performance supercapacitor applications. This study demonstrates the importance of electron transfer pathways at the interface of substrate/current collector and electroactive material for electrochemical performances of electrodes.

Hybrid composite polyaniline-nickel hydroxide electrode materials for supercapacitor applications

Pristine and nanocomposite (NC) hybrid electrodes of polyaniline (PANI)-nickel hydroxide [Ni(OH)2] have been prepared by single and two-step electrodeposition processes, respectively, onto stainless-steel (SS) substrates. Enhanced reversibility and stability of amorphous PANI- Ni(OH)2 NC electrodes compared to single electrode materials have been explored. PANI has a nanofibrous morphology, Ni(OH)2 has nanoplatelet-type morphology, and the NC electrodes retain an overall nanofibrous morphology. The maximum specific capacitance (SC), obtained from integrated charge under voltammetric conditions, for PANI (electro-deposited for 5 min), NC (electrodeposition of Ni(OH)2 for 10 min and 20 min onto PANI electrode surface) and Ni(OH)2 (electrodeposited for 10 min) electrodes, are 0.59, 39.06, 32.36, and 113.8 F/g, respectively, suggesting higher electrochemical performance of Ni(OH)2 electrode compared to PANI and NC electrodes. The retention in SC values with faster scan rates from 10 to 100 mV/s for PANI, NC (10 min), NC (20 min) and Ni(OH)2 are 38.7, 61.1, 52.4, and 29.0 %, respectively, explicitly confirming a higher reversibility in NC electrodes. The retention in SC values with increase of cycle number up to 1000 for PANI, NC (10 min), NC (20 min) and Ni(OH)2 electrodes are 34.9, 61.5, 67.5, and 40.7 % respectively, demonstrating higher electrochemical stability of NC electrodes over pure-phase electrodes. Nearly 2.15, 79.36, 66.66 and 406.83 mC/cm2 charges on PANI, NC (10 min), NC (20 min) and Ni(OH)2 electrodes, respectively, are obtained. Inner to total charge and outer to total charge ratios have been used to explain contributing sites to total charge in pristine and NC electrodes.

Towards fully polymeric electroactive micro actuators with conductive polymer electrodes

The performance of micro devices actuated using electroactive polymers is often limited by the high stiffness of metallic electrodes, which prevents the polymeric components extension. In this work we report on an approach allowing to reduce the use of metals to a minimum by incorporating softer conductive polymer electrodes. A multilayered actuator incorporating polyimide (PI) substrate and a thin electroactive polymer (EAP) layer of P(VDF-TrFE-CFE) squeezed between polyaniline (PANI) electrodes was fabricated and characterized. The PANI layer was electrodeposited on the electroactive structures using cyclic voltammetry. Our results show that while the use of conjugate conductive polymer electrodes is feasible, the influence of the thin metallic seed layers required for electro-deposition is significant. The proposed electro-deposition based polymeric process is highlighted by its simplicity and relatively low cost, compared to common Physical Vapor Deposition processes, and can be extended to other polymers.

One-pot synthesis of covalently functionalized reduced graphene oxide–polyaniline nanocomposite for supercapacitor applications

A high-performance reduced graphene oxide–polyaniline (RGO-PANI) electrode material was prepared through commercially viable, facile one-pot synthesis, applying famed diazotization chemistry and grafting strategy. In this work, 4-nitroaniline was utilized as a grafting substrate to bind reduced graphene oxide and polyaniline covalently to a highly stable and efficient supercapacitor electrode material. The chemical composition and structural analysis of covalently functionalized RGO-PANI nanocomposites were characterized by X-ray diffraction, field-emission scanning electron microscopy, Raman spectroscopy, UV–visible spectroscopy, and Fourier-transform infrared spectroscopy. The electrochemical behavior of the nanocomposites was analyzed through cyclic voltammetry, galvanostatic charge and discharge, and electrochemical impedance spectroscopy. The prepared nanocomposite shows a high specific capacitance of 490 F g−1 in 1 M Na2SO4 with outstanding cyclic stability (10,000 cycles). The applied covalent functionalization through grafting strategy was the principal factor for both high specific capacitance and excellent cyclic stability.

A high performance all-solid-state flexible supercapacitor based on carbon nanotube fiber/carbon nanotubes/polyaniline with a double core-sheathed structure

A new type of ternary carbon nanotube fiber (CNF)/three-dimensional (3D) porous carbon nanotubes (CNTs)/polyaniline (PANI) electrodes with a double core-sheathed architecture composed of CNF/CNTs and CNTs/PANI was fabricated via low-potential electrophoretic deposition of CNTs and subsequent electrochemical polymerization of PANI on the CNF surface. The resulting all-solid-state supercapacitor possesses a high specific capacitance of 67.31 mF cm−2 at the current density of 0.5 mA cm−2 and only a loss as less as 10% of its initial specific capacitance after 5000 charge-discharge cycles. Furthermore, it is capable of withstanding different bending deformations, and can maintain 99.8% capacitance, even after experiencing the bending of 180° for 500 times, which manifests a significant application potential in the field of flexible electronic devices.

Self-healing polyaniline-graphene oxides based electrodes with enhanced cycling stability

Polyaniline (PANI) is a strong competitor as a high performance supercapacitor electrode material. However, it suffers from the poor cycling life, which is caused by electrode structure damages and materials degradation occurred during charge-discharge process. Therefore, self-healing PANI-graphene oxides based electrodes have been develop with the aim to enhance the electrode structure stability. It could rebuild the electronic contact between pulverized PANI nanostructures and electrode matrix, which leads to the recovery of specific capacitance. In coral-like PANI and PANI-graphene oxides (PANI-GO) composited based self-healing devices, capacitance retention of about 93% after 9000 cycles has been achieved. In order to further supress the material degradation, aniline tetramer-graphene oxides composites (AT-GO) with lower rigidity have been synthesized. The AT-GO based self-healing device exhibits a very good cycling stability with capacitance retention up to 97.5% after 9000 cycles. It also shows a high cell specific capacitance of 143.2 F g−1 obtained at 0.5 A g−1, suggesting the good electrochemical performance. This work demonstrates the idea of using self-healing polymer to enhance the cycling stability of PANI composites based electrodes.

Selective electro-oxidation of phenol to benzoquinone/hydroquinone on polyaniline enhances capacitance and cycling stability of polyaniline electrodes

Polyaniline (PANI)-based conductive polymers are promising electrode candidates for energy storage, but they suffer the common hurdle of poor cycling stability due to structural rupture during the doping and de-doping processes. Electro-oxidation of phenol is an attractive method for removing phenol from contaminated wastewaters, but the method usually suffers from electrode fouling due to formation of non-conductive polymers on the anode. Here, we propose an environmentally benign strategy that addresses these two issues simultaneously, which can substantially enhance the cycling stability of PANI and prevent passivation of the electrode. We show that, in comparison with the bare graphite brush (GB) electrode, the PANI-GB electrode (aniline electropolymerized on GB) enables high selectivity of phenol conversion to the redox-active benzoquinone (BQ)/hydroquinone (HQ). These species are largely immobilized on the electrode, as evidenced via chemical identification and physicochemical characterization. Meanwhile, the P/40-PANI-GB electrode (obtained from CV scans of phenol on PANI-GB over 40 cycles) achieves a larger specific capacitance and, more importantly, a remarkably higher capacitance retention rate compared to the PANI-GB electrode. Such improvements are demonstrated to be caused by the availability of a second BQ/HQ redox system and the strong affinity between PANI and BQ/HQ via the interactions of π–π stacking, hydrogen bonding, and chemical doping.