纳米纤维素/还原氧化石墨烯复合材料用于高性能超级电容器

以高浓度氧化石墨烯(GO)溶液作为反应前驱体,纳米纤维素(NC)作为物理间隔物和电解液储存器,通过简单的一步水热法制备了纳米纤维素/还原氧化石墨烯(NC/rGO)复合材料,并探究了其作为超级电容器电极材料的潜力。结果如下：NC添加量为1 mL所制备的NC/rGO-1具有最佳电化学性能。基于NC/rGO-1的无黏合剂对称型超级电容器在0.3 A·g^-1的电流密度下显示出了 269.33 F·g^-1和 350.13 F·cm^-3的高质量和体积比电容,并在 10.0 A·g^-1时仍能达到 215.88 F·g^-1和 280.62 F·cm^-3(其初始值的 80.15%)。组装器件还显示出了较高的质量和体积能量密度(9.3 Wh·kg^-1和 12.13 Wh·L^-1)和出色的循环性能(10 A·g^-1下10 000次循环后其初始比电容仅减少6.02%)。     

纳米纤维素/还原氧化石墨烯复合材料用于高性能超级电容器

以高浓度氧化石墨烯(GO)溶液作为反应前驱体,纳米纤维素(NC)作为物理间隔物和电解液储存器,通过简单的一步水热法制备了纳米纤维素/还原氧化石墨烯(NC/rGO)复合材料,并探究了其作为超级电容器电极材料的潜力。结果如下：NC添加量为1 mL所制备的NC/rGO-1具有最佳电化学性能。基于NC/rGO-1的无黏合剂对称型超级电容器在0.3 A·g^-1的电流密度下显示出了269.33 F·g^-1和350.13 F·cm^-3的高质量和体积比电容,并在10.0 A·g^-1时仍能达到215.88 F·g^-1和280.62 F·cm^-3(其初始值的80.15%)。组装器件还显示出了较高的质量和体积能量密度(9.3 Wh·kg^-1和12.13 Wh·L^-1)和出色的循环性能(10 A·g^-1下10 000次循环后其初始比电容仅减少6.02%)。     

In situ synthesized heteropoly acid/polyaniline/graphene nanocomposites to simultaneously boost both double layer- and pseudo-capacitance for supercapacitors

It is challenging to simultaneously increase double layer- and pseudo-capacitance for supercapacitors. Phosphomolybdic acid/polyaniline/graphene nanocomposites (PMo(12)-PANI/GS) were prepared by using PMo(12) as a bifunctional reagent for not only well dispersing graphene for high electrochemical double layer capacitance but also in situ chemically polymerizing aniline for high pseudocapacitance, resulting in a specific capacitance of 587 F g(-1), which is ～1.5 and 6 times higher than that of PANI/GS (392 F g(-1)) and GS (103 F g(-1)), respectively. The nanocomposites also exhibit good reversibility and stability. Other kinds of heteropolyacids such as molybdovanadophosphoric acids (PMo(12-x)V(x), x = 1, 2 and 3) were also used to prepare PMo(12-x)V(x)-PANI/GS nanocomposites, also showing enhanced double layer- and pseudo-capacitance. This further proves the proposed concept to simultaneously boost both double layer- and pseudo-capacitance and demonstrates that it could be a universal approach to significantly improve the capacitance for supercapacitors.     

Hierarchical nanocomposites of polyaniline scales coated on graphene oxide sheets for enhanced supercapacitors

The homogeneous polyaniline–graphene oxide (PANI-GO) nanocomposites were facilely assembled with a redox system in which cumene hydroperoxide (CHP) and iron dichloride (FeCl₂) acted as oxidant and reductant, respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that PANI scales coated uniformly on the surface of GO sheets owing to the synergistic effect between the PANI and GO. The obtained PANI-GO nanocomposites exhibited improved electrochemical performance as an electrode material for supercapacitors compared with the pure PANI. The specific capacitance of the PANI-GO nanocomposites was high up to 308.3 F g^?1, much higher than that of the pure PANI with specific capacitance of 150 F g^?1 at a current density of 1 A g^?1 in 2 M H₂SO₄ electrolyte. The Raman and XPS results illustrated that enhanced electrochemical performance might be attributed to the π-π conjugation between the PANI and GO sheets.     

Facile synthesis of polyaniline/TiO2/graphene oxide composite for high performance supercapacitors

The polyaniline/TiO₂/graphene oxide (PANI/TiO₂/GO) composite, as a novel supercapacitor material, is synthesized by in situ hydrolyzation of tetrabutyl titanate and polymerization of aniline monomer in the presence of graphene oxide. The morphology, composition and structure of the composites as-obtained are characterized by SEM, TEM, XRD and TGA. The electrochemical property and impedance of the composites are studied by cyclic voltammetry and Nyquist plot, respectively. The results show that the introduction of the GO and TiO₂ enhanced the electrode conductivity and stability, and then improved the supercapacitive behavior of PANI/TiO₂/GO composite. Significantly, the electrochemical measurement results show that the PANI/TiO₂/GO composite has a high specific capacitance (1020 F g⁻¹ at 2 mV s⁻¹, 430 F g⁻¹ at 1 A g⁻¹) and long cycle life (over 1000 times).     

Three-dimensional ZnS/reduced graphene oxide/polypyrrole composite for high-performance supercapacitors and lithium-ion battery electrode material

Journal of Solid State Electrochemistry - In this work, three-dimensional ZnS/reduced graphene oxide/polypyrrole ternary composites were synthesized. The as-prepared composites are investigated as...     

Straightforward synthesis of conductive graphene/polymer nanocomposites from graphite oxide

The reduction of graphite oxide (GO) in the presence of reactive poly(methyl methacrylate) (PMMA), under mild biphasic conditions, directly affords graphene grafted with PMMA. The resulting nanocomposite shows excellent electrical conductivities resulting from the optimal dispersion and exfoliation of graphene in the polymer matrix.     

Self-assembled fabrication and flame-retardant properties of reduced graphene oxide/waterborne polyurethane nanocomposites

The graphite oxide (GO) was prepared from expandable graphite by the pressurized oxidation method, and samples were characterized using XRD, UV–Vis, and TEM. GO is reduced in situ emulsion using hydrazine to achieve reduced graphene oxide/waterborne polyurethane (rGO/WPU) nanocomposites. The effect of rGO content on the stability, fracture morphologies, mechanical performance, thermal degradation, and flame-retardant properties of rGO/WPU composites was investigated by zeta potential analyzer, TEM, SEM, universal testing machine, TG, and Cone Calorimeter. The results of zeta potential, TEM, and SEM analysis indicate that rGO has a good stability and dispersibility in rGO/WPU nanocomposites. The results of mechanical tests showed that the mechanical properties of rGO/WPU nanocomposites increased consistently with increasing rGO content up to 2 mass%, and TG showed that the thermostability of rGO/WPU nanocomposites decreased slightly compared to pure WPU, but carbon residue increased from 0.99 to 1.99 % when the mass fraction of rGO in WPU is 2 %. Cone Calorimeter test indicated that the flame-retardant and smoke suppression properties of rGO/WPU composites showed significant improvement compared to the WPU alone. When the mass fraction of rGO is 1 %, the total smoke release and smoke factor decreased by 25 and 38 %, respectively, compared to those of pure WPU.     

Facile synthesis of cobalt oxide/reduced graphene oxide composites for electrochemical capacitor and sensor applications

Reduced graphene oxide sheets decorated with cobalt oxide nanoparticles (Co₃O₄/rGO) were produced using a hydrothermal method without surfactants. Both the reduction of GO and the formation of Co₃O₄ nanoparticles occurred simultaneously under this condition. At the same current density of 0.5 A g⁻¹, the Co₃O₄/rGO nanocomposites exhibited much a higher specific capacitance (545 F g⁻¹) than that of bare Co₃O₄ (100 F g⁻¹). On the other hand, for the detection of H₂O₂, the peak current of Co₃O₄/rGO was 4 times higher than that of Co₃O₄. Moreover, the resulting composite displayed a low detection limit of 0.62 μM and a high sensitivity of 28,500 μA mM⁻¹cm⁻² for the H₂O₂ sensor. These results suggest that the Co₃O₄/rGO nanocomposite is a promising material for both supercapacitor and non-enzymatic H₂O₂ sensor applications.     

Electrodeposited highly-ordered manganese oxide nanowire arrays for supercapacitors

Large arrays of well-aligned Mn oxide nanowires were prepared by electrodeposition using anodic aluminum oxide templates. The sizes of nanowires were tuned by varying the electrotype solution involved and the MnO₂ nanowires with 10 μm in length were obtained in a neutral KMnO₄ bath for 1 h. MnO₂ nanowire arrays grown on conductor substance save the tedious electrode-making process, and electrochemical characterization demonstrates that the MnO₂ nanowire arrays electrode has good capacitive behavior. Due to the limited mass transportation in narrow spacing, the spacing effects between the neighbor nanowires have show great influence to the electrochemical performance.     

Mixed colloidal suspensions of reduced graphene oxide and layered metal oxide nanosheets: useful precursors for the porous nanocomposites and hybrid films of graphene/metal oxide

Homogeneously mixed colloidal suspensions of reduced graphene oxide, or RGO, and layered manganate nanosheets have been synthesized by a simple addition of the exfoliated colloid of RGO into that of layered MnO(2). The obtained mixed colloidal suspensions with the RGO/MnO(2) ratio of ≤0.3 show good colloidal stability without any phase separation and a negatively charged state with a zeta (ζ) potential of -30 to -40?mV. The flocculation of these mixed colloidal suspensions with lithium cations yields porous nanocomposites of Li/RGO-layered MnO(2) with high electrochemical activity and a markedly expanded surface area of around 70-100?m(2) g(-1). Relative to the Li/RGO and Li/layered MnO(2) nanocomposites (≈116 and ≈167?F?g(-1)), the obtained Li/RGO-layered MnO(2) nanocomposites deliver a larger capacitance of approximately 210?F?g(-1) with good cyclability of around 95-97?% up to the 1000th cycle, thus indicating the positive effect of hybridization on the electrode performances of RGO and lithium manganate. Also, an electrophoretic deposition of the mixed colloidal suspensions makes it possible to easily fabricate uniform hybrid films composed of graphene and manganese oxide. The obtained films show a distinct electrochemical activity and a homogeneous distribution of RGO and MnO(2). The present experimental findings clearly demonstrate that the utilization of the mixed colloidal suspensions as precursors provides a facile and universal methodology to synthesize various types of graphene/metal oxide hybrid materials.     

Ultrasonic route synthesis,characterization and electrochemical study of graphene oxide and reduced graphene oxide

Research on Chemical Intermediates - In this study, an efficient route for graphene oxide (GO) and reduced GO (RGO) synthesis was developed by using an ultrasonic probe and bath alternatively. RGO...     

PE-CPE blends and their graphene oxide nanocomposites with reduced low temperature brittleness

The low-temperature flexibility of polyethylene (PE)–chlorinated polyethylene (CPE) blends and their composites with a small amount of graphene oxide filler was studied. Quantitative height variation in the AFM images, rheological as well as fracture analyses were employed to gain insights into the generation of flexibility in the matrix phase. The semi-crystalline CPE (CPE25) polymer did not induce viscoelastic behavior at temperatures lower than the glass transition temperature of PE, whereas the amorphous CPE (CPE35) had completely different behavior. The samples with CPE35 could not be sufficiently hardened even at ?180 °C and remained too soft for cryosectioning. Therefore, compression, which results in a 30–60 % reduction in length along the cutting direction with no change in the dimension perpendicular to it, was very prominent for both thin section and block face of the sample. The composites had even higher degree of compression due to additional effect of weak filler matrix interactions and as a consequence, the topographical variations led to filler pull out during sectioning. It was also confirmed using the rheological analysis that composites (and blends with 10 % CPE35 content) had phase immiscibility as CPE phase was suspected to concentrate near the graphene oxide phase leading to generation of chlorine-rich phases. The addition of graphene oxide did not lead to reduced flexibility and the composites also retained the modulus similar to pure polymer. The mechanical fracture of the samples also confirmed the flexibility of the CPE containing blends and composites as these samples were still flexible at ?195 °C.     

One-pot synthesis of Fe3O4/polypyrrole/graphene oxide nanocomposites for electrochemical sensing of hydrazine

Microchimica Acta - The authors describe the synthesis of a nanocomposite consisting of Fe3O4 nanoparticles, polypyrrole and graphene oxide (Fe3O4/PPy/GO), and its application to voltammetric...     

Double laminated reduced graphene/Cu_2S/reduced graphene/graphene oxide nanofilms and their photoelectrochemical properties

In this work,an efficient photocatalytic material was prepared directly on Indium tin oxide(ITO)glass substrates by fabricating Cu_2 S and graphene oxide onto graphene for photoelectrochemical(PEC) water splitting.The double laminated reduced graphene/Cu_2S/reduced graphene/graphene oxide(RG/Cu_2S/RG/GO) nanofilms were characterized,and an enhanced photoelectrochemical response in the visible region was discovered.The photocurrent density of the nanofilms for PEC water splitting was measured to be up to 1.98 m A/cm~2,which could be ascribed to the followings:(i) a higher efficiency of light-harvesting because of GO coupling with Cu_2 S that could broaden the absorbing solar spectrum and enhance the light utilization efficiency;(ii) a stepwise structure of band-edge levels in the Cu_2S/GO electrode was constructed;(iii) double laminated electron accelerator(RG) was used in the Cu_2S/GO materials to get better electron-injecting efficiency.     

Hydrothermal synthesis of reduced graphene sheets/Fe2O3 nanorods composites and their enhanced electrochemical performance for supercapacitors

Reduced graphene nanosheets/Fe₂O₃ nanorods (GNS/Fe₂O₃) composite has been fabricated by a hydrothermal route for supercapacitor electrode materials. The obtained GNS/Fe₂O₃ composite formed a uniform structure with the Fe₂O₃ nanorods grew on the graphene surface and/or filled between the graphene sheets. The electrochemical performances of the GNS/Fe₂O₃ hybrid supercapacitor were tested by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge tests in 6 M KOH electrolyte. Comparing with the pure Fe₂O₃ electrode, GNS/Fe₂O₃ composite electrode exhibits an enhanced specific capacitance of 320 F g⁻¹ at 10 mA cm⁻² and an excellent cycle-ability with capacity retention of about 97% after 500 cycles. The simple and cost-effective preparation technique of this composite with good capacitive behavior encourages its potential commercial application.     

Double laminated reduced graphene/Cu2S/reduced graphene/graphene oxide nanofilms and their photoelectrochemical properties

In this work,an efficient photocatalytic material was prepared directly on Indium tin oxide（ITO）glass substrates by fabricating Cu₂ S and graphene oxide onto graphene for photoelectrochemical（PEC） water splitting.The double laminated reduced graphene/Cu₂S/reduced graphene/graphene oxide（RG/Cu₂S/RG/GO） nanofilms were characterized,and an enhanced photoelectrochemical response in the visible region was discovered.The photocurrent density of the nanofilms for PEC water splitting was measured to be up to 1.98 m A/cm²,which could be ascribed to the followings:（i） a higher efficiency of light-harvesting because of GO coupling with Cu₂ S that could broaden the absorbing solar spectrum and enhance the light utilization efficiency;（ii） a stepwise structure of band-edge levels in the Cu₂S/GO electrode was constructed;（iii） double laminated electron accelerator（RG） was used in the Cu₂S/GO materials to get better electron-injecting efficiency.     

Multifunctional nanocomposites based on tetraethylenepentamine-modified graphene oxide/epoxy

Composites based on epoxy/graphene were investigated for thermal-mechanical performance. Initially, few-layer graphene oxide (GO) was modified with tetraethylenepentamine (GO-TEPA) in a reaction assisted by microwave radiation. GO and GO-TEPA samples were characterized for their structure and morphology. Composites containing 0.1, 0.3 and 0.5 wt.% of GO and GO-TEPA were prepared, and the effect of fillers on the morphology of cryofractured regions of epoxy matrix was observed through electron microscopy images. Dynamic mechanical thermal analysis (DMA) tests revealed increases of approximately 20 °C in glass transition. Moreover, when compared to neat polymer, composites containing 0.5 wt.% of GO-TEPA gained up to 103% in thermal conductivity (obtained by flash laser). Finally, nanoindentation analyses showed increases of 72% in Young's modulus and 143% in hardness for the same sample. The system is characterized as multifunctional nanocomposites because of the simultaneous gains in thermal and mechanical properties. The best results of the multifunctional composites were strongly associated with the chemical modification of the GO by TEPA.