Preparation of self-supporting graphene on flexible graphite sheet and electrodeposition of polyaniline for supercapacitor

Electrochemical approach toward reduced graphene oxide-based electrodes for environmental applications: A review

Graphene has shown great potential in various application fields due to its excellent carrier transportation, ultra-high specific surface area, good mechanical properties, and light transmittance. However, pure graphene still exhibits some insurmountable defects, such as difficulty in simple and large-scale preparation, and limitations in application. The electrochemical method is a simple, clean, and environmentally friendly method. The rapid and simple preparation of graphene and its derivatives by electrochemical methods has important environmental significance. Moreover, rGO-based nanohybrids can be prepared by convenient and quick electrodeposition or cyclic voltammetry (CV), or to change the morphology and structure of graphene and its derivatives to achieve the purpose of improving material properties. This work mainly summarizes electrochemically related graphene from four aspects: (i) the method of electrochemical exfoliation of graphene; (ii) types of electrodeposition rGO-based nanohybrids; (iii) electrochemical regulation of the structure of rGO-based mixtures; (iv) environmental applications of rGO-based nanohybrids prepared by electrodeposition. This article critically discusses the advantages and disadvantages of electrochemical-related graphene, outlines future challenges, and provides insightful views and references for other researchers.

Electrochemically Exfoliated Graphene/Manganese Dioxide Nanowire Composites as Electrode Materials for Flexible Supercapacitors

Flexible supercapacitors are of great significance for the development of intelligent electronic products and wearable devices. Herein, through reasonable design, self-supporting flexible film composites that can be used as supercapacitor electrodes, are synthesised by vacuum filtration. The composites are composed of electrochemically exfoliated graphene nanosheets and MnO2 nanowires, in which the graphene nanosheets mainly play the role of skeleton support, enhance conductivity, and provide electric double-layer capacitance, while the MnO2 nanowires mainly provide pseudocapacitance. Results show that the sample with 20% MnO2 possesses the best electrochemical performance due to the mass ratio which can give full play to the pseudocapacitive properties of MnO2 and the conductivity of graphene. The maximum mass specific capacitance reaches 106.2F g−1 at 0.5A g−1, and the areal specific capacitance is 767.0mF cm−2 at 1mA cm−2. The electrode also maintains 86.7% of the initial capacitance after 10000 cycles, indicating good cyclic stability. Furthermore, an asymmetric solid supercapacitor based on flexible thin films is assembled. The energy density is 20.7Wh kg−1, the power density is 1000W kg−1, and the capacitance remains 84.2% after 3000 cycles at 5.0A g−1. These results suggest that the as-prepared self-supporting material has the potential to be used to construct flexible supercapacitors for wearable equipment.

In Situ Growth of Oriented Polyaniline Nanorod Arrays on the Graphite Flake for High-Performance Supercapacitors

Polyaniline with oriented nanorod arrays could provide high surface area and relaxed nanostructure to optimize ion diffusion paths, thus enhancing the performance of the device. In this paper, we designed an all-solid symmetrical supercapacitor with good performance based on polyaniline nanorod arrays in situ-grown on a graphite flake free-standing substrate. The specific capacitance, cycle stability, and energy density of the prepared supercapacitor device were 135 F/g, 75.4% retention after 1500 cycles, and the energy density is 18.75 W h/kg at a power density of 500 W/kg. The good performance of the supercapacitor device was obviously related to the oriented nanorod arrays of polyaniline/graphite flakes. In order to find the application of the prepared supercapacitor device, the tandem device consisting of three single supercapacitor devices connected in series had been used to drive small electronic equipment. The red light-emitting diode and chronograph could be easily driven by the 3-series supercapacitor devices. These results indicated that the prepared supercapacitor device based on the polyaniline/graphite flake electrode had potential applications in energy storage devices.

Recent Progress on Graphene/Polyaniline Composites for High-performance Supercapacitors

Electrode materials are crucial for the electrochemical performance of supercapacitors. In view of the high specific surface area, high conductivity of graphene nanosheets and the high pseudocapacitance of polyaniline (PANI), the combination of graphene with PANI has become a research hotspot. In this work, we summarize the recent advance on the synthesis of PANI and graphene/PANI composites, and their application in supercapacitors. The synthesis of PANI is the basis of preparing graphene/PANI composites, so we first introduce the synthesis methods of PANI. Then, the advances of two dimensional (2D) and three dimensional (3D) graphene/PANI composites are summarized according to the inherent feature of graphene. The 2D composites of pristine graphene and functionalized graphene with PANI are introduced separately; furthermore, the 3D composites are classified into three sections, including flexible graphene/PANI composites, graphene framework based composites, and printable graphene/PANI composites. At last, aiming at solving the current challenges of graphene/PANI composites, we put forward some strategies for preparing high performance graphene/PANI composite electrodes.

Flexible all-solid-state supercapacitors of polyaniline nanowire arrays deposited on electrospun carbon nanofibers decorated with MOFs

Porous carbons derived from metal-organic frameworks (MOFs) are promising materials for a number of energy- and environment-related applications. To integrate the powder MOFs-derived carbon into feasible engineered materials, a facile strategy to fabricate integrated flexible film is developed by growing MOFs nanoparticles on polyimide electrospun nanofibers, followed by calcination, to fabricate freestanding carbon nanofiber membranes decorated with porous carbon. Then vertically polyaniline nanowire arrays are uniformly deposited on the hierarchical porous carbon substrates by in situ polymerization. Thanks to the good distribution of MOFs-derived porous carbon on carbon nanofibers and the compact configuration interwoven by conducting polymers, the designed hybrid electrode could be used directly as a freestanding electrode for supercapacitors, which displayed a high specific capacitance of 1268 F g^-1. The assembled flexible solid-state supercapacitor based on the integrated electrodes demonstrated a high volumetric capacitance of 1973 mF cm^-3 and a good capacitance retention of 84.9% after 10 000 cycles, which could power a commercial light emitting diode. This strategy may shed light on the design of MOFs-based flexible materials for practical applications of supercapacitors and other electrochemical devices.

Conjugated Polymers for Flexible Energy Harvesting and Storage

Since the discovery of conjugated polymers in the 1970s, they have attracted considerable interest in light of their advantages of having a tunable bandgap, high electroactivity, high flexibility, and good processability compared to inorganic conducting materials. The above combined advantages make them promising for effective energy harvesting and storage, which have been widely studied in recent decades. Herein, the key advancements in the use of conjugated polymers for flexible energy harvesting and storage are reviewed. The synthesis, structure, and properties of conjugated polymers are first summarized. Then, their applications in flexible polymer solar cells, thermoelectric generators, supercapacitors, and lithium-ion batteries are described. The remaining challenges are then discussed to highlight the future direction in the development of conjugated polymers.

Flexible Supercapacitors Based on Polyaniline Arrays Coated Graphene Aerogel Electrodes

Flexible supercapacitors(SCs) made by reduced graphene oxide (rGO)-based aerogel usually suffer from the low energy density, short cycle life and bad flexibility. In this study, a new, synthetic strategy was developed for enhancing the electrochemical performances of rGO aerogel-based supercapacitor via electrodeposition polyaniline arrays on the prepared ultralight rGO aerogel. The novel hybrid composites with coated polyaniline (PANI) arrays growing on the rGO surface can take full advantage of the rich open-pore and excellent conductivity of the crosslinking framework structure of 3D rGO aerogel and high capacitance contribution from the PANI. The obtained hybrid composites exhibit excellent electrochemical performance with a specific capacitance of 432 F g^-1 at the current density of 1 A g^-1, robust cycling stability to maintain 85% after 10,000 charge/discharge cycles and high energy density of 25 W h kg^-1. Furthermore, the flexible all-solid-state supercapacitor have superior flexibility and outstanding stability under different bending states from the straight state to the 90° status. The high-performance flexible all-solid-state SCs together with the lighting tests demonstrate it possible for applications in portable electronics.

Highly flexible binder-free core-shell nanofibrous electrode for lightweight electrochemical energy storage using recycled water bottles

The creation of a novel flexible nanocomposite fiber with conductive polymer polyaniline (PAni) coating on a polyethylene terephthalate (PET) substrate allowed for increased electrochemical performance while retaining ideal mechanical properties such as very high flexibility. Binder-free PAni-wrapped PET (PAni@PET) fiber with a core-shell structure was successfully fabricated through a novel technique. The PET nanofiber substrate was fabricated through an optimized electrospinning method, while the PAni shell was chemically polymerized onto the surface of the nanofibers. The PET substrate can be made directly from recycled PETE1 grade plastic water bottles. The resulting nanofiber with an average diameter of 121 nm ± 39 nm, with a specific surface area of 83.72 m(2) g(-1), led to better ionic interactions at the electrode/electrolyte interface. The PAni active layer coating was found to be 69 nm in average thickness. The specific capacitance was found to have increased dramatically from pure PAni with carbon binders. The specific capacitance was found to be 347 F g(-1) at a relatively high scan rate of 10 mV s(-1). The PAni/PET fiber also experienced very little degradation (4.4%) in capacitance after 1500 galvanostatic charge/discharge cycles at a specific current of 1.2 A g(-1). The mesoporous structure of the PAni@PET fibrous mat also allowed for tunable capacitance by controlling the pore sizes. This novel fabrication method offers insights for the utilization of recycled PETE1 based bottles as a high performance, low cost, highly flexible supercapacitor device.

Large areal mass, flexible and freestanding polyaniline/bacterial cellulose/graphene film for high-performance supercapacitors

Flexible and freestanding electrodes with high mass loading in the range of 7–13 mg cm⁻² made of polyaniline (PANI)/bacterial cellulose (BC)/graphene (GN) conductive paper through a simple filtering method.

Flour food waste derived activated carbon for high-performance supercapacitors

Activated carbon was prepared by carbonization of flour food waste residue and subsequent KOH activation. It shows great prospects in high-performance supercapacitor applications.

Nickel hydroxide coated carbon nanoparticles mediated hybrid three-dimensional graphene foam assembly for supercapacitor

A binder-free novel three-dimensional assembly comprising graphene, carbon nanoparticles and nickel hydroxide is presented as a supercapacitor electrode.

From adsorbents to electrode materials: facile hydrothermal synthesis of montmorillonite/polyaniline/metal oxide (hydroxide) composites

Montmorillonite/polyaniline/metal oxide (hydroxide) composites are fabricated from the spent adsorbents of montmorillonite/polyaniline for the electrode materials of supercapacitors.

Low cost, high performance flexible asymmetric supercapacitor based on modified filter paper and an ultra-fast packaging technique

A low cost, high performance flexible PF–RGO//PF–RGO–PANI asymmetric supercapacitor based on modified filter paper is reported together with an ultra-fast and layer by layer packaging technique.

Nitrogen-doped reduced graphene oxide and aniline based redox additive electrolyte for a flexible supercapacitor

Nitrogen-doped reduced graphene oxide (N-rGO) with a flexible structure was prepared by simple hydrothermal method. The N-rGO flexible supercapacitor fabricated and improved the performance using aniline as redox additive.