The Experts below are selected from a list of 6378 Experts worldwide ranked by ideXlab platform
Hongtao Liu - One of the best experts on this subject based on the ideXlab platform.
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ethylene glycol reduced graphene oxide polypyrrole composite for Supercapacitor
Electrochimica Acta, 2013Co-Authors: Ya Liu, Yao Zhang, Za Wang, Kaiyu Liu, Hongtao LiuAbstract:Abstract A promising Supercapacitor Material based on graphene/polypyrrole (PPy) has been successfully synthesized via in situ oxidation polymerization of pyrrole monomers in aqueous graphene oxide (GO) solutions, followed by chemical reduction using ethylene glycol (EG). Unlike the commonly employed hydrazine reduction, the moderate EG reductant does not destruct the PPy conjugative structures, thus facilitating utilization of the electroactive conductive polymer. The morphologies and the structures of the as-prepared Materials are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectra, and Fourier transform infrared spectroscopy (FTIR). And the electrochemical performance of the fabricated electrodes was evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The EG-RGO/PPy electrode shows large specific capacitance, high rate performance, and good charge–discharge stability as well. The excellent electrochemical capability is mainly accounted for the sound composite construction that improves the effective utilization of electroactive PPy component, accelerates shuttling the charged carriers, and alleviates the swelling/shrinkage of polymer chains.
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carboxyl functionalized graphene oxide polyaniline composite as a promising Supercapacitor Material
Journal of Materials Chemistry, 2012Co-Authors: Yan Liu, Ruijie Deng, Zan Wang, Hongtao LiuAbstract:We report a novel and facile synthesis of a high-quality graphene oxide (GO)–polyaniline (PANI) composite by in situ polymerization suitable for Supercapacitor application. Unlike the use of the edged carboxyl groups of graphene sheets as linkers, the current work makes the most of the ample oxygenated groups on the basal plane of graphene sheets to combine with the amine nitrogens of the PANI chain. This is tactically realized by a carboxyl-functionalized process of GO with oxalic acid treatment prior to the combination. The as-constructed carboxyl-functionalized graphene oxide–polyaniline (CFGO–PANI) composite was roundly characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transformed infrared spectrometry (FTIR), Raman spectrometry, and thermogravimetric analysis (TGA), and a stable, highly efficient charge-transfer configuration was disclosed and confirmed. The fabricated electrode composed of this CFGO–PANI Material showed an excellent electrochemical capacitance performance with aqueous H2SO4 electrolytes.
Duo Pan - One of the best experts on this subject based on the ideXlab platform.
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a facile one pot preparation of dialdehyde starch reduced graphene oxide polyaniline composite for Supercapacitors
Electrochimica Acta, 2014Co-Authors: Liuqing Yang, Duo PanAbstract:A promising Supercapacitor Material based on dialdehyde starch reduced graphene oxide/polyaniline (DAS-RGO/PANI) composite has been successfully synthesized via in situ oxidation polymerization. In this paper, we developed a green and facile approach to the synthesis of reduced graphene oxide (RGO) based on dialdehyde starch (DAS) using exfoliated graphite oxide (GO) as precursor. The merit of this method is that both the reducing agents themselves and the oxidized products are environmentally friendly. It should be noted that, besides the mild reduction capability to GO, DAS could also play an important role as a capping reagent in stabilizing as-prepared RGO simultaneously, which exhibited good stability in water. This approach can open up the new possibility for preparing RGO in large-scale production alternatively. Moreover, DAS can reduce GO and polyaniline (PANI) in one pot to obtain DAS-RGO/PANI composite that exhibit good electrochemical properties. In addition, the DAS-RGO/PANI composite achieved the maximum specific capacitance as high as 499 F/g at a current density of 0.5 A/g, which is the highest value reported so far for graphene-doped PANI composite via a green and facile approach of reduced graphene oxide. Low resistance, long cycle life and fast reflect of oxidation/reduction on high current changes are other outstanding characteristics for the designed Supercapacitor. (C) 2014 Elsevier Ltd. All rights reserved.
Xiaogang Zhang - One of the best experts on this subject based on the ideXlab platform.
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3d porous layered double hydroxides grown on graphene as advanced electrochemical pseudocapacitor Materials
Journal of Materials Chemistry, 2013Co-Authors: Luojiang Zhang, Xiaogang Zhang, Jie Wang, Jiajia Zhu, K S Hui, Kwun Nam HuiAbstract:A 3D hybrid nickel-aluminum layered double hydroxide (NiAl-LDH)–graphene nanosheets (GNS) composite as a Supercapacitor Material has been fabricated by in situ deposition of LDH nanosheets on graphene oxide (GO) through a liquid phase deposition method. The results reveal that NiAl-LDH homogeneously grew on the surface of GNS as spacers to keep the neighboring sheets separate. Optimum effects could be achieved when feeding ratio, reaction time and temperature are tuned. The obtained porous GNS/NiAl-LDH composite exhibited high-capacitance performance with a specific capacitance of 1255.8 F g−1 at a current density of 1 A g−1 and 755.6 F g−1 at 6 A g−1, respectively. Moreover, the composite exhibited excellent cycling performance with an increase of 6% capacitance compared with the initial capacitance after 1500 cycle tests. Such high specific capacitance, rate capability and exceptional cycling ability of the composite offered great promise in energy storage device applications.
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facile synthesis and self assembly of hierarchical porous nio nano micro spherical superstructures for high performance Supercapacitors
Journal of Materials Chemistry, 2009Co-Authors: Changzhou Yuan, Xiaogang Zhang, Linhao Su, Laifa ShenAbstract:We report a practical and efficient strategy for synthesizing hierarchical (meso- and macro-)porous NiO nano/micro spherical superstructures. First, β-Ni(OH)2 microspheres were self-assembled based on the coalescence and Ostwald-ripening mechanisms during refluxing in an alkaline solution with Ni(NH3)x2+ at 97 °C for 1 h under vigorous stirring. Second, hierarchical porous NiO microsphere superstructures were obtained from the precursor by a simple calcination procedure. The resulting superstructures comprised two-dimensional mesoporous NiO petal building blocks. Electrochemical data demonstrated that the hierarchical porous NiO nano/micro superstructures were capable of delivering a specific capacitance of 710 F g−1 at 1 A g−1 and offered a good specific capacitance retention of ca. 98% after 2000 continuous charge-discharge cycles. This indicates that we successfully met key requirements in terms of large specific energy density, high-rate capability and good electrochemical stability. We would expect our superstructures to be good candidates for a low-cost replacement for the state-of-the-art Supercapacitor Material RuO2.
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Preparation and properties of Co3O4 nanorods as Supercapacitor Material
Journal of Applied Electrochemistry, 2009Co-Authors: Li Cui, Xiaogang ZhangAbstract:Co3O4 nanorods have been successfully synthesized by thermal decomposition of the precursor prepared via a facile and efficient microwave-assisted hydrothermal method, using cetyltrimethylammonium bromide (CTAB) with ordered chain structures as soft template for the first time. The obtained Co3O4 was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical measurements. The results demonstrate that the as-synthesized nanorods are single crystalline with an average diameter of about 20 to 50 nm and length up to several micrometers. Preliminary electrochemical studies, including cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) measurements, are carried out in 6 M KOH electrolyte. Specific capacitance of 456 F g−1 for a single electrode could be achieved even after 500 cycles, suggesting its potential application in electrochemical capacitors. This promising method could provide a universal green chemistry approach to synthesize other low-cost and environmentally friendly transition metal hydroxide or oxide.
Shu-hong Yu - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of Nitrogen-Doped Porous Carbon Nanofibers as an Efficient Electrode Material for Supercapacitors
ACS Nano, 2012Co-Authors: Li Feng Chen, Hai-wei Liang, Qing-fang Guan, Zhen-yu Wu, Mingguang Kong, Xu-dong Zhang, Ping Chen, Shu-hong YuAbstract:Supercapacitors (also known as ultracapacitors) are considered to be the most promising approach to meet the pressing requirements of energy storage. Supercapacitive electrode Materials, which are closely related to the high-efficiency storage of energy, have provoked more interest. Herein, we present a high-capacity Supercapacitor Material based on the nitrogen-doped porous carbon nanofibers synthesized by carbonization of macroscopic-scale carbonaceous nanofibers (CNFs) coated with polypyrrole (CNFs@polypyrrole) at an appropriate temperature. The composite nanofibers exhibit a reversible specific capacitance of 202.0 F g–1 at the current density of 1.0 A g–1 in 6.0 mol L–1 aqueous KOH electrolyte, meanwhile maintaining a high-class capacitance retention capability and a maximum power density of 89.57 kW kg–1. This kind of nitrogen-doped carbon nanofiber represents an alternative promising candidate for an efficient electrode Material for Supercapacitors.
Dacheng Zhang - One of the best experts on this subject based on the ideXlab platform.
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high performance Supercapacitors based on a graphene activated carbon composite prepared by chemical activation
RSC Advances, 2012Co-Authors: Yao Chen, Haitao Zhang, Xiong Zhang, Dacheng ZhangAbstract:Graphene has been widely applied as a promising Supercapacitor Material based on the electric double-layer mechanism. In order to solve the dispersed problem of graphene, noncovalent functionalized graphene is prepared. However, not all of these functionalized graphene Materials can be employed in Supercapacitors due to non-electrochemically activated molecules absorbed on graphene. Here we find a route of chemical activation with KOH to transfer noncovalent functionalized graphene to a graphene–activated carbon composite with a high specific surface area. Stable graphene colloids absorbed by oligomers of p-phenylene diamine was produced during the reduction of graphite oxide. KOH can homogeneously contact the solid graphene nanosheets after drying the colloid. Chemical activation by annealing the graphene based hybrid with KOH leads to a greatly increased specific surface area of 798 m2 g−1. The resulting graphene–activated carbon composite has a good capacitance of 122 F g−1 and energy density of 6.1 Wh kg−1 in aqueous electrolyte. The Supercapacitor exhibits maximum energy densities of 52.2 and 99.2 Wh kg−1 in an ionic liquid electrolyte at room temperature and 80 °C, respectively.