Flexible and robust reduced graphene oxide/carbon nanoparticles/polyaniline (RGO/CNs/PANI) composite films: Excellent candidates as free-standing electrodes for high-performance supercapacitors

Hydrothermal synthesis of rGO and MnCoS composite for enhanced supercapacitor application

Nanostructured materials incorporating transition metal sulfides have demonstrated considerable potential across various applications, particularly in the realms of energy production and storage. Sulfide-based material preparation is a challenging and costly procedure that requires a high temperature and reducing atmosphere. This work reports that manganese cobalt sulfide (MCS) and reduced graphene oxide composite manganese cobalt sulfide (rMCS) were successfully prepared through a hydrothermal method. Various characterization techniques were employed to analyze the prepared materials, including X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, and X-ray photoelectron spectroscopy. In a three-electrode system, MCS and rMCS electrodes exhibit an excellent specific capacitance of 1695 and 1925 F g-1 at 1 A g-1 current density respectively. MCS delivers the capacitance retention of 99% and rMCS exhibits the capacitance retention of 100% capacitance retention over 5000 consecutive cycles. The constructed asymmetric supercapacitor electrode (rMCS//rGO) exhibits the energy and power density of 64 Wh kg-1 at 799 W kg-1, respectively with outstanding cyclic stability of 97.4% even after 10,000 cycles. The exceptional electrochemical properties of MCS with rGO composite electrode indicate that they would make an outstanding electrode material for cutting-edge energy storage devices.

Supramolecular recognition enhanced electrochemical sensing: β-cyclodextrin and Pd nanoparticle co-decorated 3D reduced graphene oxide nanocomposite-modified glassy carbon electrode for the quantification of ractopamine

Ractopamine (RAC) is universally known for improving lean meat percentage in livestock and thus is widely introduced as a feed additive. However, it is difficult to eliminate the RAC residue in animal tissues from the biological system and will inevitably harm human health. Hence, detecting RAC molecules in biological samples is extremely significant. Herein, a novel strategy of supramolecular recognition-enhanced electrochemical sensing is presented. This platform was constructed by coupling β-cyclodextrin (β-CD) with palladium nanoparticles (Pd NPs)-functionalized three-dimensional reduced graphene oxide (3D-rGO) to form a nanocomposite (3D-rGO/Pd/β-CD), which was further used to modify a glassy carbon electrode (GCE) for RAC detection. Benefiting from the attractive electrical conductivity and catalytic activity of 3D-rGO/Pd, as well as the unique small-molecule-recognition ability of β-CD demonstrated by ¹H NMR spectrum, which revealed the 1 : 2 binding mode of RAC with β-CD, increased peak current signals of RAC were observed in the cyclic voltammetry (CV) test. Under optimized conditions, the wide linear concentration range spanned 1-95 μM, along with a relatively low detection limit of 0.12 μM (S/N = 3), as evidenced by the differential pulse voltammetry (DPV) approach. The platform also exhibited satisfactory stability and fine reproducibility, as well as high selectivity and good anti-interference capability. Moreover, this as-obtained sensor was efficiently applied in pork samples with a high recovery rate (96.44-103.99%), which provides a promising view of its electrochemical biosensing ability in practical applications.

Fabrication of Coral-like Polyaniline/Continuously Reinforced Carbon Nanotube Woven Composite Films for Flexible High-Stability Supercapacitor Electrodes

The electrochemical performance is significantly influenced by the structure and surface morphology of the electrode materials used in supercapacitors. Using the floating catalytic chemical vapor deposition (FCCVD) technique, a self-supporting, flexible layer of continuously reinforced carbon nanotube woven film (CNWF) was developed. Then, polyaniline (PANI) was formed in the conductive network of CNWF using cyclic voltammetry electrochemical polymerization (CVEP) in various aqueous electrolytes to produce a series of flexible CNWF/PANI composite films. The impacts of the CVEP period, electrolyte type, and electrolyte concentration on the surface morphology, doping degree, and hydrophilicity of CNWF/PANI composite films were thoroughly examined. The CNWF/PANI₁-15C composite electrode, which was created using 15 cycles of CVEP in a solution of 1 M sodium bisulfate, displayed a distinctive coral-like PANI layer with a well-defined sharp nanoprotuberance structure, a 48% doping degree, and a quick reversible pseudocapacitive storage mechanism. At a current density of 1 A g^-1, the energy density and specific capacitance reached 54.9 Wh kg^-1 and 1098.0 F g^-1, respectively, with a specific capacitance retention rate of 75.9% maintained at 10 A g^-1. Both the specific capacitance and coulomb efficiency were maintained at 96.9% and more than 98.1% of their initial values after being subjected to 2000 cycles of galvanostatic charge and discharge, demonstrating excellent electrochemical cycling stability. The CNWF/PANI₁-15C composite film, an ideal electrode material, offers a promising future in the field of flexible energy storage due to its exceptional mechanical properties (127.9 MPa tensile strength and 16.2% elongation at break).

Carboxymethylcellulose-polyaniline/carbon nanotube (CMC-PANI/CNT) film as flexible and highly electrochemical active electrode for supercapacitors

Herein, we demonstrate a flexible, structural robust and highly electrochemical active film electrode based on evenly distributed carboxymethylcellulose-polyaniline/carbon nanotube (CMC-PANI/CNT) for supercapacitors. In this process, vertically aligned PANI nanoparticles grow in an orderly manner on CMC fibers. The highly dispersed CNT nanomaterials are then introduced by simple layer-by-layer assembly, eventually forming an interwoven network structure. Mechanical tests have shown that the obtained CMC-PANI/CNT film exhibit excellent robustness and flexibility, and can be used directly as electrodes without any conductive additives and binders. The CMC-PANI/CNT electrode with optimal CMC, PANI and CNT contents demonstrates an excellent area specific capacitance of 3106.3 mF cm^-2 at 5 mA cm^-2 and a gravimetric specific capacitance of 348.8 F g^-1 at 0.5 A g^-1. Furthermore, the symmetric supercapacitor (SSC) assembled with CMC-PANI/CNT exhibits a high energy density of 99.89 μW h cm^-2 at a power density of 400.02 μW cm^-2, and a good cycling stability (with capacitance retention of 89.2 % after 5000 cycles). The cost-effective and eco-friendly preparation method of free-standing CMC-PANI/CNT film electrodes provide a novel insight for developing flexible energy storage devices.

Enhancing Seebeck coefficient and electrical conductivity of polyaniline/carbon nanotube–coated thermoelectric fabric

In this work, flexible thermoelectric fabrics, polyester/yarn fabrics coated with polyaniline/carbon nanotube (PANI/CNT) nanocomposite, were fabricated by sequential processing: (I) polyaniline/carbon nanotube nanocomposites preparation by a one-step in-situ polymerization and (II) dip coating of a mixture solution of CNT-doped PANI on a polyester/yarn fabric. Nanocomposites were synthesized with various CNT content (0.5, 2.5, 5, and 10 wt%) and characterized using different methods. The Seebeck coefficient and electrical conductivity measurements were used to determine their thermoelectric properties. The results revealed significant improvement in both electrical conductivity and the Seebeck coefficient with the addition of CNT. The electrical conductivity increased from 0.011 to 0.1345 S/cm with the increment of CNT from 0.5 to 10 wt%. The highest Seebeck coefficient of 11.4 μV/K was observed for the sample containing 5 wt% CNT at 338 K where the maximum power factor of 1.598×10−3 μWm−1K−2 was obtained for the fabric coated with nanocomposite containing 10 wt% CNT.

Paracetamol degradation via electrocatalysis with B and N co-doped reduced graphene oxide: Insight into the mechanism on catalyst surface and in solution

This paper presents the use of B and N co-doped reduced graphene oxide (BN-GN) as an electrode for paracetamol electrochemical degradation. The reaction mechanism, focused on active sites in the atom level and dominant radical species generated through the reaction, was analyzed by characterization, density functional theory (DFT) calculation, quenching experiments, and electron paramagnetic resonance analysis. The characterization results indicated that the introduction of N and B functionalities into GN improved catalytic activity due to the generation of new surface defects, active sites, and improvement of conductivity. Results of experiments and DFT showed that co-doping of B and N greatly improved the catalytic activity, and the B atoms in C-N-B groups were identified as main active sites. The main active substances of BN-GN generated in the electrocatalytic oxidation of paracetamol in the solution were O₂^•- and active chlorine. The influence of O₂^•- and active chlorine on the efficiency/path of catalytic oxidation and the proposed mechanism were also determined for paracetamol degradation. This study provides an in-depth understanding of the mechanism of BN-GN catalysis and suggests possibilities for practical applications.

Continuously Reinforced Carbon Nanotube Film Sea-Cucumber-like Polyaniline Nanocomposites for Flexible Self-Supporting Energy-Storage Electrode Materials

The charge storage mechanism and capacity of supercapacitors completely depend on the electrochemical and mechanical properties of electrode materials. Herein, continuously reinforced carbon nanotube film (CNTF), as the flexible support layer and the conductive skeleton, was prepared via the floating catalytic chemical vapor deposition (FCCVD) method. Furthermore, a series of novel flexible self-supporting CNTF/polyaniline (PANI) nanocomposite electrode materials were prepared by cyclic voltammetry electrochemical polymerization (CVEP), with aniline and mixed-acid-treated CNTF film. By controlling the different polymerization cycles, it was found that the growth model, morphology, apparent color, and loading amount of the PANI on the CNTF surface were different. The CNTF/PANI-15C composite electrode, prepared by 15 cycles of electrochemical polymerization, has a unique surface, with a "sea-cucumber-like" 3D nanoprotrusion structure and microporous channels formed via the stacking of the PANI nanowires. A CNTF/PANI-15C flexible electrode exhibited the highest specific capacitance, 903.6 F/g, and the highest energy density, 45.2 Wh/kg, at the current density of 1 A/g and the voltage window of 0 to 0.6 V. It could maintain 73.9% of the initial value at a high current density of 10 A/g. The excellent electrochemical cycle and structural stabilities were confirmed on the condition of the higher capacitance retention of 95.1% after 2000 cycles of galvanostatic charge/discharge, and on the almost unchanged electrochemical performances after 500 cycles of bending. The tensile strength of the composite electrode was 124.5 MPa, and the elongation at break was 18.9%.

Acetylcholinesterase sensor based on PANi/rGO film electrochemically grown on screen‐printed electrodes

In this work, the polyaniline/reduced graphene oxide (PANi/rGO) bilayer was directly electrodeposited on carbon screen‐printed electrodes (SPE). Some details in growth of PANi/rGO bilayer were revealed from cyclic voltammograms and X‐ray photoelectron spectra. The growth of stacked rGO film at high compactness on the electrode surface is mainly accompanied with reduction of epoxy functional groups at basal planes of graphitic flakes. The as‐grown rGO layer with abundent hydroxyl functional groups at basal planes is preferable to attract intrinsic fibrillar‐like PANi polymer chains in protonated aqueous media. The as‐prepared PANi/rGO hybrid bilayer has shown good conductivity, high porosity, good adhesion to biomolecules, and fast electron transfer rate (increased by 3.8 times). Herein, PANi/rGO film has been further utilized to develop disposable acetylcholinesterase sensors able to detect acetylthiocholine (ATCh) with apparent Michaelis ‐ Menten constant of 0.728 mM. These sensors provide a very promising technical solution for in‐situ monitoring acetylthiocholine level in patients with neuro‐diseases and determination of neuro‐toxins such as sarin and pesticides.

Preparation of Slightly Crumpled Aminated Graphene Nanosheets for Honeycomb-Like Flexible Graphene/PANI Composite Film Electrode with Enhanced Capacitive Performance in Solid-State Supercapacitors

Slightly crumpled aminated graphene nanosheets were prepared via the mild surface modification of graphene oxide (GO) nanosheets with p-phenylenediamine at room temperature to inhibit the restacking of graphene but avoid cross-linking during the solvothermal or microwave-assisted treatments, and then the honeycomb-like flexible graphene/polyaniline (PANI) composite film electrode, PANI@rPGO, was developed by the facile vacuum filtration and reduction. Owing to the slightly crumpled PGO nanosheets with surface amino groups, the honeycomb-like PANI@rPGO composite film, with a well-defined dispersion of PANI nanorods in the graphene-based matrix and the hierarchically porous structure, possessed superior electrochemical performance as a robust electrode in flexible solid-state supercapacitors (SSCs). The symmetric SSCs based on the PANI@rPGO electrode possessed a high capacitance of 564.5 F/g and 2015.2 mF/cm² at 0.5 A/g (2.2 mA/cm²), superior cyclic life with retentions of 104.2 and 78.5% after 2000 and 5000 cycles at 3 A/g, as well as excellent flexibility. The mild one-pot preparation and the superior electrochemical performance make the designed PANI@rPGO composite film electrode a potential candidate for high-performance flexible SSCs.

A Facile and Green Synthesis of a MoO2-Reduced Graphene Oxide Aerogel for Energy Storage Devices

A simple, low cost, and "green" method of hydrothermal synthesis, based on the addition of l-ascorbic acid (l-AA) as a reducing agent, is presented in order to obtain reduced graphene oxide (rGO) and hybrid rGO-MoO₂ aerogels for the fabrication of supercapacitors. The resulting high degree of chemical reduction of graphene oxide (GO), confirmed by X-Ray Photoelectron Spectroscopy (XPS) analysis, is shown to produce a better electrical double layer (EDL) capacitance, as shown by cyclic voltammetric (CV) measurements. Moreover, a good reduction yield of the carbonaceous 3D-scaffold seems to be achievable even when the precursor of molybdenum oxide is added to the pristine slurry in order to get the hybrid rGO-MoO₂ compound. The pseudocapacitance contribution from the resulting embedded MoO₂ microstructures, was then studied by means of CV and electrochemical impedance spectroscopy (EIS). The oxidation state of the molybdenum in the MoO₂ particles embedded in the rGO aerogel was deeply studied by means of XPS analysis and valuable information on the electrochemical behavior, according to the involved redox reactions, was obtained. Finally, the increased stability of the aerogels prepared with l-AA, after charge-discharge cycling, was demonstrated and confirmed by means of Field Emission Scanning Electron Microscopy (FESEM) characterization.

Hierarchical Porous RGO/PEDOT/PANI Hybrid for Planar/Linear Supercapacitor with Outstanding Flexibility and Stability

Many hybrid electrodes for supercapacitors (SCs) are a reckless combination without proper structural design that keeps them from fulfilling their potential. Herein, we design a reduced graphene oxide/poly(3,4-ethylenedioxythiophene)/polyaniline (RGO/PEDOT/PANI) hybrid with hierarchical and porous structure for high-performance SCs, where components fully harness their advantages, forming an interconnected and conductive framework with substantial reactive sites.Thus, this hybrid achieves a high capacitance of 535 F g-1 along with good rate capability and cyclability. The planar SC based on this hybrid deliver an energy density of 26.89 Wh kg-1 at a power density of 800 W kg-1. The linear SC developed via modifying a cotton yarn with the hybrid exhibits good flexibility and structural stability, which operates normally after arbitrary deformations. This work provides a beneficial reference for developing SCs.

An ionic liquid-modified RGO/polyaniline composite for high-performance flexible all-solid-state supercapacitors

An IL-modified RGO/polyaniline composite was obtained by hydrothermal treatment and in situ polymerization, and used for high-performance supercapacitors.

Well-defined poly(1,5-diaminoanthraquinone)/reduced graphene oxide hybrids with superior electrochemical property for high performance electrochemical capacitors

Conducting polymers and their hybrids have attracted significant attention in electrochemical capacitors due to their unique electrochemical properties. However, the poorer cycle life and lower rate capability have greatly restricted their practical applications. Herein, well-defined poly(1,5-diaminoanthraquinone)/reduced graphene oxide hybrids (PDAA/rGO) with excellent electrochemical performance were successfully prepared via in-situ chemical oxidation polymerization of 1,5-diaminoanthraquinone (DAA) using HClO₄ as initiator and (NH₄)₂S₂O₈ as oxidant in organic solvent mixture at room 25 °C. The electrochemical tests showed that the optimized one, PDAA/rGO S-2 with PDAA nanoparticles of 50 nm uniformly immobilized, possessed the specific capacitance of 617F g^-1 at the current density of 1 A g^-1 in 1.0 mol L^-1 H₂SO₄ electrolyte and outstanding rate capability with the capacitance retention of 70% even at a high current density of 20 A g^-1. Moreover, superior cycle life was achieved to about 124% of its initial capacitance at 100 mV s^-1 after 15,000 cycles without attenuation, and the symmetric solid-state supercapacitor (SSC) based on the PDAA/rGO S-2 electrodes remained 79% of its initial specific capacitance after 15,000 CV cycles.

Improved thermomechanical and electrical properties of reduced graphene oxide reinforced polyaniline - dodecylbenzenesulfonic acid/divinylbenzene nanocomposites

HYPOTHESIS

Various efforts are going on to improve the electrical properties of carbon fiber reinforced polymer (CFRP) composites. Conducting polymer is one the promising material to achieve the desired electrical properties of CFRP composites without compromising the mechanical properties as a lighting sticking material.

EXPERIMENTS

In present study, in addition to conducting polymer polyaniline (PANI), another conducting phase reduced graphene oxide (RGO) was incorporated in PANI based system. The RGO was synthesized and incorporated in different weight (0-0.5 wt%) fraction in dodecylbenzenesulfonic acid (DBSA) doped PANI-divinylbenzene (DVB) polymer to get PANI-DBSA/DVB nanocomposite. The mechanical and interfacial interaction was analyzed by universal testing machine (UTM) and transmitted electron microscopy (TEM).

FINDINGS

The addition of optimum 0.3 wt% RGO improved flexural strength and modulus of PANI-DSBA/RGO-DVB composite by 153% and 32% respectively over neat PANI-DBSA/DVB nanocomposite. The maximum electrical conductivity 0.301 S/cm, glass transition temperature (T_g) and thermal stability of nanocomposite realized at 0.3 wt% of RGO. Raman spectroscopy and HRTEM confirmed the improvement of interfacial bonding by H-bonding and π-π interaction. For the 1st time we are reporting RGO utilisation for the improvement of thermomechanical and electrical interfacial properties of PANI-DBSA/DVB nanocomposite for the structural applications.