High-performance asymmetric supercapacitor based on hierarchical nanocomposites of polyaniline nanoarrays on graphene oxide and its derived N-doped carbon nanoarrays grown on graphene sheets

Effect of Graphene Oxide Addition on the Properties of Electrochemically Synthesized Polyaniline-Graphene Oxide Films

In this work, the electrochemical synthesis of PANI and GO-modified PANI was performed using cyclic voltammetry, varying the amount of GO, 1 mg (PG1), 5 mg (PG5), and 10 mg (PG10) to analyze the effect of the amount of GO on the composite. PANI, PG1, PG5, and PG10 materials were characterized using optical microscopy, SEM, UV-vis, FTIR, Raman, and wettability. A stability test was also carried out by putting the materials to 500 oxidation-reduction cycles using cyclic voltammetry. The synthesis method allowed GO in PANI to be added through a chemical interaction between the two compounds. It was also found that the addition of GO led to an improvement in the hydrophilic character of the composite, which would lead to an improvement in the diffusion of reagents/species when the composites are used in aqueous media processes. The results of the stability test showed that the PG10 material presented a lower % loss of specific capacitance and energy compared with the other materials, which indicates that the GO presence (in the amount specified) improves the stability of the PANI. The PG10 material showed favorable and promising conditions for its use in fuel cell and battery processes.

Polyaniline-graphene based composites electrode materials in supercapacitor: synthesis, performance and prospects

Supercapacitors (SCs) have become one of the most popular energy-storage devices for high power density and fast charging/discharging capability. Polyaniline is a class of conductive polymer materials with ultra-high specific capacitance, and the excellent mechanical properties will play a key role in the research of flexible SCs. The synergistic effect between polyaniline and graphene is often used to overcome their respective inherent shortcomings, thus the high-performance polyaniline-graphene based nanocomposite electrode materials can be prepared. The development of graphene-polyaniline nanocomposites as electrode materials for SCs depends on their excellent microstructure design. However, it is still difficult to seek a balance between graphene performance and functionalization to improve the weak interfacial interaction between graphene and polyaniline. In this manuscript, the latest preparation methods, research progress and research results of graphene-polyaniline nanocomposites on SCs are reviewed, and the optimization of electrode structures and performances is discussed. Finally, the prospect of graphene-polyaniline composites is expected.

Study on Direct Synthesis of Energy Efficient Multifunctional Polyaniline-Graphene Oxide Nanocomposite and Its Application in Aqueous Symmetric Supercapacitor Devices

The synthesis of promising nanocomposite materials can always be tricky and depends a lot on the method of synthesis itself. Developing such synthesis routes, which are not only simple but also can effectively catch up the synergy of the compositing material, is definitely a worthy contribution towards nanomaterial science. Carbon-based materials, such as graphene oxide, and conjugative polymers, such as conductive polyaniline, are considered materials of the 21st century. This study involves a simple one pot synthesis route for obtaining a nanocomposite of polyaniline and graphene oxide with synergistic effects. The study was carried out in a systematic way by gradually changing the composition of the ingredients in the reaction bath until the formation of nanocomposite took place at some particular reaction parameters. These nanocomposites were then utilized for the fabrication of electrodes for aqueous symmetric supercapacitor devices utilizing gold or copper as current collectors. The device manifested a good capacitance value of 264 F/g at 1 A/g, magnificent rate performance, and capacitance retention of 84.09% at a high current density (10 A/g) when gold sheet electrodes were used as the current collectors. It also showed a capacitance retention of 79.83% and columbic efficiency of 99.83% after 2000 cycles.

Achieving Ultrahigh Cycling Stability and Extended Potential Window for Supercapacitors through Asymmetric Combination of Conductive Polymer Nanocomposite and Activated Carbon

Conducting polymers and carbon-based materials such as graphene oxide (GO) and activated carbon (AC) are the most promising capacitive materials, though both offer charge storage through different mechanisms. However, their combination can lead to some unusual results, offering improvement in certain properties in comparison with the individual materials. Cycling stability of supercapacitors devices is often a matter of concern, and extensive research is underway to improve this phenomena of supercapacitive devices. Herein, a high-performance asymmetric supercapacitor device was fabricated using graphene oxide–polyaniline (GO@PANI) nanocomposite as positive electrode and activated carbon (AC) as negative electrode. The device showed 142 F g⁻¹ specific capacitance at 1 A g⁻¹ current density with capacitance retention of 73.94% at higher current density (10 A g⁻¹). Most importantly, the device exhibited very high electrochemical cycling stability. It retained 118.6% specific capacitance of the starting value after 10,000 cycles at 3 Ag⁻¹ and with coulombic efficiency of 98.06 %, indicating great potential for practical applications. Very small solution resistance (Rs, 0.640 Ω) and charge transfer resistance (Rct, 0.200 Ω) were observed hinting efficient charge transfer and fast ion diffusion. Due to asymmetric combination, potential window was extended to 1.2 V in aqueous electrolyte, as a result higher energy density (28.5 Wh kg⁻¹) and power density of 2503 W kg⁻¹ were achieved at the current density 1 Ag⁻¹. It also showed an aerial capacitance of 57 mF cm⁻² at current 3.2 mA cm⁻². At this current density, its energy density was maximum (0.92 mWh cm⁻²) with power density (10.47 W cm⁻²).

Polydopamine modified polyaniline-graphene oxide composite for enhancement of corrosion resistance

In this study, the composite of two-dimensional graphene oxide (GO) nanosheets and button-shaped polyaniline (PANI) was synthesized and further modified by polydopamine (PDA). The obtained PDA-PANI-GO composite was used to enhance the corrosion protection ability of nontoxic water-based alkyd varnish (WAV). The chemical composition, functional groups and surface morphologies of GO, PANI-GO and PDA-PANI-GO composites were characterized by XRD, FT-IR XPS and SEM. The anticorrosion performance was demonstrated by electrochemical impedance spectroscopy measurements and polarization tests. Due to the physical barrier effects and surface hydrophobicity of PANI-GO composite, the approaches of the caustic substances to the surface of the metal was inhibited, while the highly adhesive PDA molecules reinforced compatibility between fillers and WAV. As results, PDA-PANI-GO composite introduced WAV enhanced corrosion prevention performance. Under the optimal conditions, where the ratio of PDA to PANI-GO was kept at 2:1, the impedance values increased by over two orders of magnitude compared with bare steel.

Improving electrochemical performance of reduced graphene oxide by counteracting its aggregation through intercalation of nanoparticles

Herein, we report the fabrication and characterization of hybrid electrode material for supercapacitor applications. CaCO₃ nanoparticles (Nps) are used as intercalator to avoid the restacking behavior of reduced graphene oxide (rGO) nanosheets. CaCO₃ Nps and rGO sheets are fabricated employing precipitation technique and microwave irradiation method, respectively. The intercalation process is performed by magnetic stirring followed by ultra-sonication technique. As prepared CaCO₃ Nps, rGO and rGO intercalated with 2.5 wt.% and 5 wt.% CaCO₃ Nps are characterized using X-ray diffraction analysis, Fourier transform infrared spectroscopy and field emission scanning electron microscopy to evaluate the crystalline characteristics, molecular vibrations, and morphology, respectively. The prepared electrode materials are coated separately on the glassy carbon electrode and their electrochemical performance displayed remarkable capacitance values for rGO nanosheets intercalated with 2.5 wt.% and 5 wt.% CaCO₃ Nps. From the obtained results, it is clear that the specific capacitance of 2.5 wt.% CaCO₃ intercalated rGO displays higher specific capacitance of 84.5 F/g at 5 mV/s with high retention stability. The mechanism behind the improvement in the electrochemical behavior is due to the increase in active surface area which is explained via Brunauer-Emmett-Teller analysis and energy-dispersive X-ray spectroscopic analysis.

Poly(1,5-diaminoanthraquinone) coated carbon cloth composites as flexible electrode with extraordinary cycling stability for symmetric solid-state supercapacitors

Poly(1,5-diaminoanthraquinone) (PDAA) coated carbon cloth (ROCC@PDAA) composites were fabricated as flexible electrode by in-situ chemical oxidation polymerization of 1,5-diaminoanthraquinone (DAA) on the surface of oxidized carbon cloth (OCC) using ammonium persulfate (APS) as oxidant in the mixture of N,N-dimethylformamide/acetonitrile by refluxing with HClO₄ as initiator, followed by reducing the OCC with hydrazine. The optimized flexible composites possessed high areal capacitance of 1.3 F cm^-2 (specific capacitance of 81.9 F g^-1) at the current density of 1 mA cm^-2 with excellent rate properties (61% at 20 mA cm^-2) and extraordinary cycling stability (159% after 20,000 cycles). The flexible symmetric solid-state supercapacitor (SSC) constructed with the optimized ROCC@PDAA composite could light up a red light emitting diode, also exhibited excellent electrochemical performance with remarkable mechanical and flexible properties. All the results demonstrated the potential application of the proposed ROCC@PDAA composites for flexible energy storage devices.

Graphene-based nano composites and their applications. A review

The purpose of the current review article is to present a comprehensive understanding regarding pros and cons of graphene related nanocomposites and to find ways in order to improve the performance of nanocomposites with new designs. Nanomaterials including GR are employed in industrial applications such as supercapacitors, biosensors, solar cells, and corrosion studies. The present article has been prepared in three main categories. In the first part, graphene types have been presented, as pristine graphene, graphene oxide and reduced graphene oxide. In the second part, nanocomposites with many graphene, inorganic and polymeric materials such as polymer/GR, activated carbon/GR, metal oxide/GR, metal/graphene and carbon fibre/GR have been investigated in more detail. In the third part, the focus in on the industrial applications of GR nanocomposite, including super capacitors, biosensors, solar cells, and corrosion protection studies.

Rational Surface Tailoring Oxygen Functional Groups on Carbon Spheres for Capacitive Mechanistic Study

Porous carbons represent a typical class of electrode materials for electric double-layer capacitors. However, less attention has been focused on the study of the capacitive mechanism of electrochemically active surface oxygen groups rooted in porous carbons. Herein, the degree and variety of oxygen surface groups of HNO₃-modified samples (N-CS) are finely tailored by a mild hydrothermal oxidation (0.0-3.0 mol L^-1), while the micro-meso-macroporous structures are efficiently preserved from the original sample. Thus, N-CS is a suitable carrier for separately discussing the contribution of oxygen functional groups to the electrochemical property. The optimized N-CS shows a high capacitance of 279.4 F g^-1 at 1 A g^-1, exceeding 52.8% of pristine carbon sphere (CS) (182.8 F g^-1 at 1 A g^-1) in KOH electrolyte. On further deconvoluting the redox peaks of cyclic voltammetry curves, we find that the pseudocapacitance not only associates with the surface-controlled faradic reaction at high scan rate but also dramatically stems from the diffusion-controlled capacitance through potassium and hydroxyl ion insertion/deinsertion into the underutilized micropores at low scan rate. The assembled supercapacitor based on N-CS presents a stable energy density of 5 Wh kg^-1 over a wide range of power density of 250-5000 W kg^-1, which is higher than 0.0N-CS in KOH electrolyte. In TEABF₄ electrolyte, the N-CS supercapacitor has an energy density of 26.9 Wh kg^-1 at the power density of 1350 W kg^-1 and exhibits excellent cycling stability with a capacitance retention of 93.2% at 2 A g^-1 after 10 000 cycles. These results demonstrate that surface oxygen groups alter the capacitive mechanism and contribution of porous carbons.

A Review of Supercapacitors Based on Graphene and Redox-Active Organic Materials

Supercapacitors are a highly promising class of energy storage devices due to their high power density and long life cycle. Conducting polymers (CPs) and organic molecules are potential candidates for improving supercapacitor electrodes due to their low cost, large specific pseudocapacitance and facile synthesis methods. Graphene, with its unique two-dimensional structure, shows high electrical conductivity, large specific surface area and outstanding mechanical properties, which makes it an excellent material for lithium ion batteries, fuel cells and supercapacitors. The combination of CPs and graphene as electrode material is expected to boost the properties of supercapacitors. In this review, we summarize recent reports on three different CP/graphene composites as electrode materials for supercapacitors, discussing synthesis and electrochemical performance. Novel flexible and wearable devices based on CP/graphene composites are introduced and discussed, with an eye to recent developments and challenges for future research directions.

Nickel molybdate nanorods supported on three-dimensional, porous nickel film coated on copper wire as an advanced binder-free electrode for flexible wire-type asymmetric micro-supercapacitors with enhanced electrochemical performances

Wire-shaped micro-supercapacitors attracted extensive attentions in next-generation portable and wearable electronics, due to advantages of miniature size, lightweight and flexibility. Herein, NiMoO₄ nanorods supported on Ni film coated Cu wire are successfully fabricated thorough direct deposition of Ni film onto Cu wire as the conductive substrate, followed by growth of the NiMoO₄ nanorods on Ni film coated Cu wire substrate by means a hydrothermal annealing process. The prepared 3D, porous electrode demonstrates extremely high areal specific capacitance of 12.03F cm^-2 at the current density of 4 mA cm^-2 and retained capacitance of 8.23 F cm^-2 at a much higher current density of 80 mAcm^-2. The electrode, also, shows an excellent cycling stability with capacitance retention of 99.3% after 3000 cycles. The superior electrochemical performance can be attributed to the high area surface, low contact resistance between NiMoO₄ nanorods and Cu wire current collector and presence of a 3D and porous structure provides many electroactive sites and sufficient open space for easy diffusion of the electrolyte ions during redox reactions. Benefiting from their structural features, a fiber shaped asymmetric micro-supercapacitor based on NiMoO₄/Ni film/Cu wire as the positive electrode and carbon fiber coated with reduced graphene oxide as the negative electrode is assembled. The fabricated fiber device presents a wide potential window between 0 and 1.7 V and exhibits high specific capacitance of 0.504F cm^-2 (38.8F cm^-3) at a current density of 4.8 mA cm^-2 with a high energy density of 202 µWh cm^-2 (15.6 mWh cm^-3) at a power density of 4050 µW cm^-2 (313 mWh cm^-3). The energy density retains 124 µWh cm^-2 (9.54 mWh cm^-3) when the power density is increased to 13530 µW cm^-2 (1040.73 mWh cm^-3). In addition, the asymmetric device exhibits an outstanding cycling stability (98.5% capacitance retention after 1000 consecutive cycles) and good mechanical stability. Therefore, this work suggested the promising potential of NiMoO₄ nanorods supported on Ni film coated Cu wire as an advanced electrode material for construction of flexible and portable next-generation energy storage micro-devices with superior electrochemical performances.

Glucose/Graphene-Based Aerogels for Gas Adsorption and Electric Double Layer Capacitors

In this study, three-dimensional glucose/graphene-based aerogels (G/GAs) were synthesized using the hydrothermal reduction and CO₂ activation method. Graphene oxide (GO) was used as a matrix, and glucose was used as a binder for the orientation of the GO morphology in an aqueous media. We determined that G/GAs exhibited narrow mesopore size distribution, a high surface area (763 m² g-1), and hierarchical macroporous and mesoporous structures. These features contributed to G/GAs being promising adsorbents for the removal of CO₂ (76.5 mg g-1 at 298 K), CH₄ (16.8 mg g-1 at 298 K), and H₂ (12.1 mg g-1 at 77 K). G/GAs presented excellent electrochemical performance, featuring a high specific capacitance of 305.5 F g-1 at 1 A g-1, and good cyclic stability of 98.5% retention after 10,000 consecutive charge-discharge cycles at 10 A g-1. This study provided an efficient approach for preparing graphene aerogels exhibiting hierarchical porosity for gas adsorption and supercapacitors.