超级电容器用聚苯胺／活性炭复合电极的研究

通过循环伏安法在多孔活性炭表面沉积了聚苯胺膜,并采用扫描电子显微镜、交流阻抗潜以及恒电流允放电技术对聚苯胺、活性炭和聚苯胺/活性炭复合电极进行了研究.结果显示:聚苯胺在活性炭表面形成一层由多孔网状结构组成的均匀的膜.聚苯胺/活性炭复合电极比活性炭电极具有更高的容量,同时比聚苯胺电极具有更好的循环稳定性.聚苯胺/活性炭复合电极的比电容为587F/g,而活性炭电极仅为140F/g.在50次充放电循环后,聚苯胺电极比电容从513降至334F/g,而聚苯胺/活性炭复合电极从415F/g下降为383F/g.     

Amperometric biosensor based on carbon nanotubes coated with polyaniline/dendrimer-encapsulated Pt nanoparticles for glucose detection

A novel amperometric glucose biosensor based on the nanocomposites of multi-wall carbon nanotubes (CNT) coated with polyaniline (PANI) and dendrimer-encapsulated Pt nanoparticles (Pt-DENs) is prepared. CNT coated with protonated PANI is in situ synthesized and Pt-DENs is absorbed on PANI/CNT composite surface by self-assembly method. Then Glucose oxidase (GOx) is crosslink-immobilizated onto Pt-DENs/PANI/CNT composite film. The results show that the fabricated GOx/Pt-DENs/PANI/CNT electrode exhibits excellent response performance to glucose, such as low detection limit (0.5 µM), wide linear range (1 µM–12 mM), short response time (about 5 s), high sensitivity (42.0 µA mM^? 1 cm^? 2) and stability (83% remains after 3 weeks).     

Thermal behavior of functionalized conventional polyaniline with hydrothermally synthesized graphene/carbon nanotubes

Abstract

Conventional polyaniline (PANI) was mixed as a binder polymer matrix with carbonous materials. Hydrothermal technique was utilized to fabricate a nanocomposite of graphene (G)/carbon nanotubes (CNTs). The morphological features and quality of the synthesized PANI, G/CNTs, and their mixtures were investigated. Scanning electron microscopy (SEM) images confirm the formation of wide area graphene sheets with folds around the edges. In addition, the hydrothermally fabricated G/CNTs exhibited a uniform distribution with partial agglomeration. However, adding their mixture to PANI generated a mesh like porous morphology which demonstrates an enhancement in surface area and providing 3D conduction network. Moreover, Raman spectra confirm the quality of the synthesized samples. The generated disorder and defects within the structure, and the ratio of quinoid ring (Q) to benzenoid (B) ring in the fabricated samples were depicted. In addition, the enhancement in thermal parameters and reversing the thermo-electric carrier type into N-type after doping were attributed to the generated facile conduction paths of G/CNTs.     

Effects of the surface treatment on the properties of polyaniline coated carbon nanotubes/epoxy composites

The effects of a surface treatment of carbon nanotubes (CNTs) on the electrical conductivity and the hydrophilicity of a polyaniline (PAni) coated CNTs (PAni-CNTs)/epoxy (EP) composites were examined. The surface of the CNTs was treated with various chemicals, such as acid mixtures (HNO₃:H₂SO₄), potassium persulfate (KPS) and sodium dodecyl sulfate (SDS), to improve their dispersion and reactivity with PAni. The electrical conductivity and hydrophilicity of PAni-CNTs and their EP composites were strongly affected by the surface treatment of the CNTs. The surface-treating materials remained on the surface of the CNTs affected the reactivity of the CNTs surface to PAni, and thus resulted in different PAni amounts in the PAni-CNTs. The electrical conductivity of the PAni-CNTs/EP composites decreased, but the hydrophilicity increased, with increasing the amount of PAni coating on the CNTs surface.     

Dynamic and static fracture analyses of graphene sheets and carbon nanotubes

Dynamic and static fracture properties of Graphene Sheets (GSs) and Carbon nanotubes (CNTs) with different sizes are investigated based on an empirical inter-atomic potential function that can simulate nonlinear large deflections of nanostructures. Dynamic fracture of GSs and CNTs are studied based on wave propagation analysis in these nanostructures in a wide range of strain-rates. It is shown that wave propagation velocity is independent from strain-rate while dependent on the nanostructure size and approaches to 2.2 × 10⁴ m/s for long GSs. Also, fracture strain shows extensive changes versus strain-rate, which has not been reported before. Fracture stress is determined as 115 GPa for GSs and 122 GPa for CNTs which are independent from the strain-rate; in contrast to the fracture strain. Moreover, fracture strain drops at extremely high strain-rates for GSs and CNTs. These features are considered as capability of carbon nanostructures for reinforcing nanocomposites especially under impact loadings up to high strain-rates.     

Fracture and progressive failure of defective graphene sheets and carbon nanotubes

An atomistic based finite bond element model for the prediction of fracture and progressive failure of graphene sheets and carbon nanotubes is developed by incorporating the modified Morse potential. The element formulation includes eight degrees of freedom reducing computational cost compared to the 12 degrees of freedom used in other FE type models. The coefficients of the elements are determined based on the analytical molecular structural mechanics model developed by the authors. The model is capable of predicting the mechanical properties (Young’s moduli, Poisson’s ratios and force–strain relationships) of both defect-free and defective carbon nanotubes under different loading conditions. In particular our approach is shown to more accurately predict Poisson’s ratio. The numerical prediction of nonlinear stress–strain relationships for defect-free nanotubes including ultimate strength and strain to failure of nanotubes is identical to our analytical molecular structural mechanics solution. An interaction based mechanics approach is introduced to model the formation of Stone–Wales (5-7-7-5) topological defect. The predicted formation energy is compared with ab initio calculations. The progressive failure of defective graphene sheets and nanotubes containing a 5-7-7-5 defect is studied, and the degradation of Young’s moduli, ultimate strength and failure strains of defective nanotubes is predicted.     

All-solid-state flexible supercapacitors based on papers coated with carbon nanotubes and ionic-liquid-based gel electrolytes

All-solid-state flexible supercapacitors were fabricated using carbon nanotubes (CNTs), regular office papers, and ionic-liquid-based gel electrolytes. Flexible electrodes were made by coating CNTs on office papers by a drop-dry method. The gel electrolyte was prepared by mixing fumed silica nanopowders with ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf(2)]). This supercapacitor showed high power and energy performance as a solid-state flexible supercapacitor. The specific capacitance of the CNT electrodes was 135 F g(-1) at a current density of 2 A g(-1), when considering the mass of active materials only. The maximum power and energy density of the supercapacitors were 164 kW kg(-1) and 41 Wh kg(-1), respectively. Interestingly, the solid-state supercapacitor with the gel electrolyte showed comparable performance to the supercapacitors with ionic-liquid electrolyte. Moreover, the supercapacitor showed excellent stability and flexibility. The CNT/paper- and gel-based supercapacitors may hold great potential for low-cost and high-performance flexible energy storage applications.     

Surfactant-assisted synthesis of reduced graphene oxide/polyaniline composites by gamma irradiation for supercapacitors

A series of graphene materials are prepared by intercalation of graphene oxide (GO) with different surfactants, cetyltrimethylammonium bromide (CTAB), n-octyltrimethylammonium bromide, tetramethylammonium bromide, and sodium dodecylbenzene sulfonate, subsequently by γ-ray induced reduction in N-methyl-2-pyrrolidone (NMP) at room temperature. GO can be reduced by the electrons generated from the radiolysis of NMP under γ-ray irradiation, and reduced GO is simultaneously functionalized by the radiolytic product of NMP. Cationic surfactant CTAB with longer alkyl chains can effectively promote the reduction process of GO by preventing the aggregation of graphene sheets, which has been testified by X-ray photoelectron spectroscopy, X-ray diffraction, thermogravimetric analysis, Raman spectroscopy, and Fourier transform infrared spectroscopy analyses. Furthermore, when the as-prepared graphene/polyaniline composites are used for supercapacitor electrode materials, there is a highest specific capacitance of 484 F g^?1 at a current density of 0.1 A g^?1 for the graphene produced in the presence of cationic surfactant CTAB.     

超级电容器用聚苯胺/有序介孔炭复合电极的性能

利用原位聚合法制备了聚苯胺/有序介孔炭复合材料.通过恒流充放电、循环伏安和交流阻抗测试考察了不同聚苯胺含量对聚苯胺/有序介孔炭复合材料电化学性能的影响.研究表明:与纯的有序介孔炭和聚苯胺相比,聚苯胺/有序介孔炭复合材料具有更高的比容量,良好的稳定性和充放电循环性能.当聚苯胺质量分数为60%,电流密度为0.1A·g-1时,比容量可以达到409F·g-1.     

Hybrids of carbon nanotubes and graphene/graphene oxide

This paper reviews recent progress in hybrids based on carbon nanotubes (CNTs) and graphene (G) or graphene oxide (GO). The combination of CNTs, including single-walled (SW), double-walled (DW) and multi-walled (MW), and G or GO resulted in various hybrids. CNTs–G/GO hybrid thin films are usually prepared by using solution/suspension casting and layer-by-layer (LbL) deposition, free-standing sheets are fabricated by using vacuum filtration and 3D hierarchical structures are produced by using chemical vapor deposition (CVD). CNTs–G/GO hybrids have also been used as fillers to fabricate polymer composites with synergistic effects. The composites have significantly improved electrical, mechanical and thermal properties, which make them very useful for various potential applications, such as transparent electrodes replacing ITO, electrodes for supercapacitors, lithium-ion batteries and dye-sensitized solar cells.     

A novel and simple nitrogen-doped carbon/polyaniline electrode material for supercapacitors

We demonstrated a simple and environment-friendly method in thepreparation of N-doped carbon/PANI(NCP)composite without binder.The structureand the property of NCP have been characterized by XPS,IR,XRD,SEM,CV,GCD and EIS.The results reveal that NCP has high capacitance performance of up to 615 F·g^-1at 0.6A·g^-1.Additionally,the asymmetric NCP₃₀₀/lcarbon supercapacitor delivers a highcapacitance(111 F·g^-1at 1A·g^-1)and a capacity retention rate of 82%after 1200 cyclesat 2A·g^-1.The ASC cell could deliver a high energy density of 39.1 W·h·kg^-1at a powerdensity of 792.6 W·kg^-1.     

Synergistic effects from graphene and carbon nanotubes enable flexible and robust electrodes for high-performance supercapacitors

Flexible and lightweight energy storage systems have received tremendous interest recently due to their potential applications in wearable electronics, roll-up displays, and other devices. To manufacture such systems, flexible electrodes with desired mechanical and electrochemical properties are critical. Herein we present a novel method to fabricate conductive, highly flexible, and robust film supercapacitor electrodes based on graphene/MnO(2)/CNTs nanocomposites. The synergistic effects from graphene, CNTs, and MnO(2) deliver outstanding mechanical properties (tensile strength of 48 MPa) and superior electrochemical activity that were not achieved by any of these components alone. These flexible electrodes allow highly active material loading (71 wt % MnO(2)), areal density (8.80 mg/cm(2)), and high specific capacitance (372 F/g) with excellent rate capability for supercapacitors without the need of current collectors and binders. The film can also be wound around 0.5 mm diameter rods for fabricating full cells with high performance, showing significant potential in flexible energy storage devices.     

Vibrational analysis of carbon nanotubes and graphene sheets using molecular structural mechanics approach

In this article, the vibrational properties of two kinds of single-layered graphene sheets and single-wall carbon nanotubes (SWCNT) are studied. The simulations are carried out for two types of zigzag carbon nanotubes (6,0), (12,0), armchair carbon nanotubes (4,4), (6,6) and zigzag and armchair graphene sheets with free-fixed and fixed–fixed end conditions.Fundamental frequency is determined by means of molecular structural mechanics approach. In this approach, carbon nanotubes (CNTs) and grapheme sheets are considered as space frames. By constructing equality between strain energies of each element in structural mechanics and potential energies of each bond, equivalent space frames can be achieved. Carbon atoms are considered as concentrated masses placed in beam joints (bond junctions).Results are presented as diagrams stating fundamental frequencies of nanotubes and graphene sheets with respect to aspect ratios. The results indicate that fundamental frequency decreases as aspect ratio increases. So it is preferred to use nanotubes and graphene sheets with lower aspect ratios for dynamic applications in order to prevent resonance and dynamic damage. Fundamental frequency of nanotubes is larger than that of graphene sheets. The results are in good agreement with results of previous researches.     

Growth of carbon nanotubes on aluminium foil for supercapacitors electrodes

A new approach for the preparation of carbon nanotubes (CNTs) electrode is proposed in the present work. Multi-walled carbon nanotubes (MWCNTs) were grown by chemical vapour deposition on aluminium strips pre-plated with a nickel thin film as the catalyst. The CNTs were characterized by scanning and transmission electron microscopy, Brunauer–Emmett–Teller surface area measurement and thermogravimetric analysis. The nickel-plated aluminium foil with a layer of CNTs was further characterized for an assessment of its electrochemical behaviour as electrode for supercapacitors. The specific capacitances of the electrode, as derived from cyclic voltammetry measurement at 0.1 V s⁻¹ scan rate, was found to be 54 and 79 F g⁻¹ in aqueous and organic electrolytes, respectively, in line with the highest reported values for either activated carbon or MWCNTs electrodes. Further evidence in support of the viability of the present approach for the preparation of a CNTs electrode was obtained from electrochemical impedance spectroscopy.     

Rational synthesis of carbon shell coated polyaniline/MoS<Subscript>2</Subscript> monolayer composites for high-performance supercapacitors

Conducting polymers generally show high specific capacitance but suffer from poor rate capability and rapid capacitance decay, which greatly limits their practical applications in supercapacitor electrodes. To this end, many studies have focused on improving the overall capacitive performance by synthesizing nanostructured conducting polymers or by depositing a range of coatings to increase the active surface area exposed to the electrolyte and enhance the charge transport efficiency and structural stability. Despite this, simultaneously achieving high specific capacitance, good rate performance, and long cycle life remains a considerable challenge. Among the various two-dimensional (2D) layered materials, octahedral (1T) phase molybdenum disulfide (MoS₂) nanosheets have high electrical conductivity, large specific surface areas, and unique surface chemical characteristics, making them an interesting substrate for the controlled growth of nanostructured conducting polymers. This paper reports the rational synthesis of carbon shell-coated polyaniline (PANI) grown on 1T MoS₂ monolayers (MoS₂/PANI@C). The composite electrode comprised of MoS₂/PANI@C with a ~3 nm carbon shell exhibited a remarkable specific capacitance of up to 678 F·g^–1 (1 mV·s^–1), superior capacity retention of 80% after 10,000 cycles and good rate performance (81% at 10 mV·s^–1) due to the multiple synergic effects between the PANI nanostructure and 1T MoS₂ substrates as well as protection by the uniform thin carbon shell. These properties are comparable to the best overall capacitive performance achieved for conducting polymers-based supercapacitor electrodes reported thus far.

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High-performance asymmetric supercapacitors based on reduced graphene oxide/polyaniline composite electrodes with sandwich-like structure

The sandwich-like structure of reduced graphene oxide/polyaniline(RGO/PANI) hybrid electrode was prepared by electrochemical deposition. Both the voltage windows and electrolytes for electrochemical deposition of PANI and RGO were optimized. In the composites, PANI nanofibers were anchored on the surface of the RGO sheets, which avoids the re-stacking of neighboring sheets. The RGO/PANI composite electrode shows a high specific capacitance of 466 F/g at 2 m A/cm~2 than that of previously reported RGO/PANI composites. Asymmetric flexible supercapacitors applying RGO/PANI as positive electrode and carbon fiber cloth as negative electrode can be cycled reversibly in the high-voltage region of 0–1.6 V and displays intriguing performance with a maximum specific capacitance of 35.5 m F cm~(-2). Also, it delivers a high energy density of 45.5 m W h cm~(-2) at power density of 1250 m W cm~(-2). Furthermore, the asymmetric device exhibits an excellent long cycle life with 97.6% initial capacitance retention after 5000 cycles.Such composite electrode has a great potential for applications in flexible electronics, roll-up display,and wearable devices.     

Active carbon/graphene hydrogel nanocomposites as a symmetric device for supercapacitors

Activated carbons (ACs) are successfully synthesized from Elaeagnus grain by a simple chemical synthesis methodology and demonstrated as novel, suitable supercapacitor electrode materials for graphene hydrogel (GH)/AC nanocomposites. GH/AC nanocomposites are synthesized via hydrothermal process at temperature of 180°C. The low-temperature thermal exfoliation approach is convenient for mass production of graphene hydrogel (GH) at low cost and it can be used as electrode material for energy storage applications. The GH/AC nanocomposites exhibit better electrochemical performances than the pure GH. Electrochemical performance of the electrodes is studied by cyclic voltammetry, and galvanostatic charge-discharge measurements in 1.0 M H₂SO₄ solution. A remarkable specific capacitance of 602.36 Fg^?1 (based on GH/AC nanocomposites for 0.4 g AC) is obtained at a scan rate of 1 mVs^?1 in 1 M H₂SO₄ solution and 155.78 Fg^?1 for GH. The specific capacitance was increased 3.87 times for GH/AC compared to GH electrodes. Moreover, the GH/AC nanocomposites for 0.2 g AC present excellent long cycle life with 99.8% specific capacitance retained after 1000 charge/discharge processes. Herein, ACs prepared from Elaeagnus grain are synthesized GH and AC supercapacitor device for high-performance electrical energy storage devices as a promising substitute to conventional electrode materials for EDLCs.     

Electric-field-induced microstructure modulation of carbon nanotubes for high-performance supercapacitors

The growth direction, morphology and microstructure of carbon nanotubes (CNTs) play key roles for their potential applications in electronic and energy storage devices. However, effective synthesis of CNTs in high crystallinity and desired microstructure still remains a tremendous challenge. Here we introduce an electric field for controlling the microstructure formation of CNTs. It reveals that the electric field not only make CNTs aligned parallel but also improve the density of CNTs. Especially, the microstructures of CNTs gradually change under electrical field. That is, graphite sheets are transformed from the “herringbone” structure to a highly crystalline structure, facilitating the transportation of electrons. Due to the improved aligned growth direction, high density and highly crystalline microstructure, the electrochemical performance of CNTs is greatly improved. When the CNTs are applied in supercapacitors, they present a high specific capacitance of 237 F/g, three times higher than that of the CNTs prepared without electrical field. Such microstructure modulation of CNTs by electric field would help to construct high performance electronic and energy storage devices.     

The effect of plasma treatment on flexible self-standing supercapacitors composed by carbon nanotubes and multilayer graphene composites

Journal of Materials Science - Flexible self-standing supercapacitor devices (FSSS) have attracted great attention in several areas due to their potential use in a wide range of applications, such...