Thermal stability and electrochemical performance of Polyaniline/Pr6O11 composites

In order to describe the influence of Pr₆O₁₁ on thermal and electrochemical performance of polyaniline (PANI), PANI/Pr₆O₁₁ composites were synthesized by in situ polymerization in the presence of sulfosalicylic acid (as dopant). The composites obtained was characterized by scanning electron microscope, Fourier transform infrared spectra, and X‐ray diffraction. The thermal stability of the composites was investigated by thermogravimetry and derivative thermogravimetry. Finally, the comparative analysis on the electrochemical properties of PANI/Pr₆O₁₁ composites electrodes, such as cyclic voltammetry, electrochemical impedance spectroscopy, and constant current charge–discharge test, was conducted under similar conditions. Scanning electron microscope, infrared, and X‐ray diffraction results show that interaction exists between PANI and Pr₆O₁₁, and the composites are more crystalline than pure PANI. Thermogravimetry and derivative thermogravimetry analyses indicate that PANI/Pr₆O₁₁ composites and pure PANI have similar thermal stability. Moreover, the studies regarded to capacitive properties show that the electrochemical performance of the composites is improved greatly when Pr₆O₁₁ is added in small amount. However, with increasing the amount of Pr₆O₁₁, the electrochemical performance of the composites become worse, which indicates a large amount of Pr₆O₁₁ has a negative effect on the capacitance. These results suggest that PANI is still in the conductive form after inserting the Pr₆O₁₁, and the capacitance performance of PANI can be improved only by a low percentage of Pr₆O₁₁. Copyright © 2013 John Wiley & Sons, Ltd.     

Thermal stability of several polyaniline/rare earth oxide composites III

Polyaniline/Nd₂O₃ (PANI/Nd₂O₃) composites were synthesized by in situ polymerization at the presence of sulfosalicylic acid (as dopant). The composites obtained were characterized by Fourier transform infrared spectra (FTIR) and X-ray diffraction (XRD). The thermal stability of the composites was investigated by thermogravimetry (TG) and derivative thermogravimetry (DTG). The electrochemical performance of the composites was investigated by cyclic voltammetry (CV). The results of FTIR, XRD, and CV show that the structure of composite has changed greatly when Nd₂O₃ content is ≥0.7 g and the PANI in the composite has transformed into pernigraniline base (non-conducting state) from emeraldine base (conducting state). TG–DTG analysis indicates that the thermal stability of PANI/Nd₂O₃ composites was higher than the pure PANI.     

Thermal stability of several polyaniline/rare earth oxide composites

Polyaniline/rare earth oxide composites (PANI/La₂O₃ and PANI/Sm₂O₃) were synthesized by in situ polymerization at the presence of sulfosalicylic acid (as dopant). The composites obtained were characterized by Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermal stability of the composites was investigated by thermogravimetry (TG) and derivative thermogravimetry (DTG). The electrochemical performance of the composites was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results of FTIR, XRD, SEM, CV, and EIS show that the structure of composite has changed greatly when rare earth oxide content is >0.7 g (PANI/La₂O₃[w/w(92.7/7.3)] and PANI/Sm₂O₃[w/w(96.2/3.8)]) and the PANI in the composite has transformed into pernigraniline base (non-conducting state) from emeraldine base (conducting state). TG-DTG analysis indicates that the thermal stability of composite was higher than pure PANI, which is attributed to the interaction between PANI and rare earth oxide.     

Preparation and Characterization of In-Situ Polymerized Nanocomposites Based on Polyaniline in Presence of MWCNTs

Summary: Polyaniline (PANI) composites were prepared with both unmodified and amine modified MWCNTs with and without BaTiO₃ through in-situ oxidative polymerization. Uniform coating of PANI on the MWCNTs and BaTiO₃ surfaces was found which was evident from the Field Emission Scanning Electron Microscopic (FESEM) and High Resolution Transmission Electron Microscopic (HRTEM) images. The structure of pure and amine modified MWCNTs was identified by Fourier Transform Infrared Spectroscopy (FTIR). The thermal stability of the amine modified composite with BaTiO₃ is higher than that of the unmodified composite because of the better affinity between modified MWCNTs and polymer matrix and due to the higher stability of barium titanate itself. The capacitance of amine modified MWCNTs and BaTiO₃ composites was less than that of the pure MWCNTs composites but the thermal stability increased in amine modified MWCNTs and BaTiO₃ composites with respect to the pure MWCNTs composites. The maximum capacitance and energy density values were found in MWCNT/PANI composites which were equal to 523.20 F/g and 142.83 Wh/kg respectively at a scan rate of 10mv/s. Maximum power density was found to be 5147.70 W/kg in the same composite at a scan rate of 200 mv/s.     

Ball milling: An effective technique for the preparation of exfoliated clay filled unsaturated polyester toughened epoxy nanocomposite

This paper investigates the possibility of improving the mechanical and thermal properties of epoxy and unsaturated polyester toughened epoxy resins through the dispersion of octadecyl ammonium ion-exchanged montmorillonite (organoclay) through exfoliated mechanism. The nanocomposites prepared are characterized for their structural change and studied for their crystallite size, mechanical, thermal and water absorption (hydrophilicity) properties. The mechanical data indicates significant improvement in the flexural and tensile properties over the neat epoxy and UP-epoxy matrix according to the percentage content of organoclay. The thermal behavior too shows noticeable enhancement in glass transition temperature T _g and high thermal stability. Hydrophilicity of all the composites decreases irrespective of the concentration of organoclay on the epoxy and UP-epoxy matrices. The homogeneous morphology of epoxy and UP toughened epoxy nanocomposite hybrid systems is ascertained using scanning electron microscope (SEM). X-ray results point out that the cetyl ammonium modified clay filled composites exhibited the exfoliated structure.     

Self-sustaining hybrid electrode prepared from polyaniline,carbon nanotubes,and carbon fibers: morphological,structural, and electrochemical analyses

The self-sustaining hybrid electrode was prepared via chemical polymerization of aniline in acid medium containing dispersed carbon nanotubes (CNT), using carbon fiber (CF) as conducting substrate. The ternary composites called PAni/CNT/CF were characterized in order to evaluate their morphologies, structures, and thermal properties. The influence of the polyaniline (PAni) layer in the ternary composite properties was studied considering different deposition times on CF samples (30, 60, and 90 min). The ternary composite morphologies were observed by scanning electron microscopy while thermal structural analyses were obtained using thermogravimetric measurements. The structural features were analyzed by Raman scattering spectroscopy and Fourier transform infrared spectroscopy (FTIR). The possible interactions between PAni and CNT were discussed on the basis of Raman and FTIR spectra. These spectroscopic analyses also confirmed that the PAni present in the composite is in the emeraldine (ES) salt form. Furthermore, the ternary composites were also evaluated by electrochemical measurements such as cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) techniques. The results showed good charge storage capacity for ternary composites, in particular, for PAni/CNT/CF obtained with 90 min of deposition time, which exhibited specific capacitance of around 500 F g^?1. Therefore, this electrode was selected to build a prototype of type I supercapacitor. This device presented specific capacitance of around 143 F g^?1 after 3200 charge/discharge cycles.     

Fe3O4/N-rGO复合材料的制备及其电化学电容性能

通过简单的一步水热法成功制备了Fe_3O_4/氮掺杂还原石墨烯(Fe_3O_4/N-r GO)复合物电极材料。采用X-射线衍射、X-射线光电子能谱、扫描电镜和透射电镜等手段对其结构和形貌进行了表征,用循环伏安法、交流阻抗和恒电流充放电等方法研究了所制备材料的电化学性能。结果表明,Fe_3O_4/N-rGO具有更高的比电容和更好的循环稳定性,在0.5A/g的电流密度下,其比电容高达291.7F/g,远高于纯的Fe_3O_4和纯的NrGO的比电容。这是由于小粒径Fe_3O_4的加入大大降低了石墨烯的团聚,两者间的协同作用使复合物的比电容得到了提高。     

Impact of graphene on the enhancement of electrochemical and photocatalytic performance of Gd2O3 - Graphene nanocomposites

Gadolinium oxide - Graphene (Gd₂O₃-G) nanocomposites were prepared with different weight ratio of graphene using low temperature solution process. The structural, morphological, electrochemical and photocatalytic properties of the composites were investigated by X-ray diffraction, Raman, FE-SEM, HRTEM, Cyclic voltammetric and photo-degradation analysis. The chemical composition of the composites was studied by elemental mapping analysis using EPMA. The binding states of various elements present in the composites were analyzed by XPS. Cyclic voltammetric studies revealed that the nanocomposite with 5% graphene exhibits the specific capacitance of 26 F g⁻¹, which is higher than that of pure Gd₂O₃ (18 F g⁻¹). The presence of graphene has greatly enhanced the photocatalytic performance of Gd₂O₃G composites as the rate of degradation of MB dye is relatively higher in the composites compared to pure Gd₂O₃. The significant increase in the specific capacitance and rate of degradation of dye suggest that the Gd₂O₃G is a promising material for energy storage and environmental applications.     

Synthesis, characterization and thermal analysis of polyaniline/ZrO2 composites

Conducting polyaniline-zirconium dioxide (PANI/ZrO₂) composites were synthesized by ‘in situ’ deposition technique in the presence of hydrochloric acid (HCl) as dopant by adding the fine grade powder (average particle size of approximately 20 nm) of ZrO₂ into the polymerization reaction mixture of aniline. The composites obtained were characterized by infrared spectra (IR) and X-ray diffraction (XRD) and thermogravimetric analysis (TGA). TG curves and DTG curves of the composites suggest that the thermal degradation process of PANI/ZrO₂ composites proceeds in two-steps and the composites are more thermally stable than that of the pure PANI. The improvement in the thermal stability for the composites is attributed to the interaction between PANI and ZrO₂, which restricts the thermal motion of PANI chains and shields the degradation of PANI in the composites.     

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).     

EQCM study of redox properties of PEDOT/MnO<Subscript>2</Subscript> composite films in aqueous electrolytes

Electrochemical behavior of poly-3,4-ethylenedioxythiophene composites with manganese dioxide (PEDOT/MnO₂) has been investigated by cyclic voltammetry and electrochemical quartz crystal microbalance at various component ratios and in different electrolyte solutions. The electrochemical formation of PEDOT film on the electrode surface and PEDOT/MnO₂ composite film during the electrochemical deposition of manganese dioxide into the polymer matrix was gravimetrically monitored. The mass of manganese dioxide deposited into PEDOT at different time of electrodeposition and apparent molar mass values of species involved into mass transfer during redox cycling of PEDOT/MnO₂ composites were evaluated. It was found that during the redox cycling of PEDOT/MnO₂ composite films with various MnO₂ content, the oppositely directed fluxes of counterions (anions and cations) occur, resulting in a change of the slope of linear parts of the Δf–E plots with changing the mass fraction of MnO₂ in the composite film.Rectangular shape of cyclic voltammograms of PEDOT/MnO₂ composites with different loadings of manganese dioxide was observed, which is characteristic of the pseudocapacitive behavior of the composite material. Specific capacity values of PEDOT/MnO₂ composites obtained from cyclic voltammograms were about 169 F g^?1. The specific capacity, related to the contribution of manganese dioxide component, was about 240 F g^?1.     

活性炭表面担载氧化锰复合电极的电化学电容性能

通过在两种商品活性炭XC-72(比表面250m2·g-1)和YEC-8(比表面1726m·2g-1)电极表面涂刷Mn(NO3)2,并在200℃进行热分解得到表面担载氧化锰的复合材料电极.采用扫描电子显微镜(SEM)和X射线衍射(XRD)表征电极的形貌和氧化锰的晶体结构,采用循环伏安、恒流充放电和交流阻抗考察了不同电极的电化学电容性能.结果表明,Mn(NO3)2在200℃的热解产物是α-Mn2O3和α-Mn3O4的混合物.当C和MnOx的质量比为2∶1和9∶1时,XC-72/MnOx中氧化锰的比电容分别达到499和435F·g-1,YEC-8/MnOx中氧化锰的比电容分别达到554和606F·g-1,表明氧化锰的赝电容对电极比电容的贡献十分显著.     

Performance improvement of EPDM and EPDM/Silicone rubber composites using modified fumed silica,titanium dioxide and graphene additives

In this work, a polymeric composite was prepared from ethylene propylene diene monomer (EPDM) and silicone rubber (S) with additives of modified fumed silica (MFS), titanium dioxide (TiO₂) and graphene. The dielectric and thermal performances of the EPDM-based composites were studied. An increase in the dielectric constant and AC dielectric breakdown strength was observed for the EPDM rubber composites containing MFS, TiO_2, and graphene additives. In addition, the incorporation of the additives resulted7in a significant increase in the thermal stability (~30–50 °C) and thermal conductivity (~7–35%) of the composites. The combination of these various improvements gives suitable performance advantage to the polymeric composite for use in insulating applications.     

无模板剂合成用于超级电容器的二氧化锰/石墨烯复合材料

以尿素、四水合氯化锰和氧化石墨烯为原料,采用水热法并通过热分解制备了一种具有石墨烯包覆结构的石墨烯-二氧化锰复合材料,利用扫描电子显微镜、X射线衍射、比表面积（BET）、拉曼光谱和热失重等技术对其形貌、晶体结构及表面结构进行了表征;在三电极条件下利用循环伏安法、恒流充放电法和交流阻抗法测试了材料的电化学性能,并考察了不同石墨烯含量对材料比电容的影响. 结果表明,在不添加模板剂的条件下制备的复合材料中二氧化锰是具有介孔结构的α-MnO₂,当复合15%（质量分数）的石墨烯后材料的比表面积从109 m²·g^-1提高到168 m²·g^-1. 复合材料具有更好的电化学性能,在0.2 A·g^-1电流密度下复合材料的比电容达到最大值（454 F·g^-1）,远高于纯二氧化锰的值（294 F·g^-1）. 在2 A·g^-1的电流密度下恒流充放电2000 次后复合材料的比电容保持率为92%.     

Growth of vertically aligned carbon nanotubes on carbon fiber: thermal and electrochemical treatments

Composite electrodes of vertically aligned carbon nanotubes (VACNT) were synthesized on carbon fiber (CF) substrate by pyrolysis of camphor/ferrocene using a SiO₂ interlayer as a barrier against metal diffusion into the substrate. Two treatments were used to remove iron from CF/VACNT structure: thermal annealing at high temperature under inert atmosphere and electrochemical oxidation in H₂SO₄ solution. The composites were characterized by scanning electron microscopy and Raman scattering spectroscopy. Besides, the electrochemical behavior of CF/VACNT was analyzed by cyclic voltammetry and charge/discharge tests. CF/VACNT composite submitted to the electrochemical oxidation showed the best electrochemical performance, with high specific capacitance, which makes it very attractive as electrode for supercapacitors.     

纳米CuFe_2O_4-rGO复合材料的制备及电化学性能

采用溶剂热法成功制备了纳米CuFe_2O_4-rGO复合材料。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和电化学工作站对样品的结构、形貌及电容特性进行表征。结果表明,CuFe_2O_4纳米粒子均匀地分散在石墨烯片层间,其中CuFe_2O_4-20%rGO复合材料具有最优的电化学性能,当电流密度1 A·g~(-1)时,其比电容为1 952.5 F·g~(-1),当电流密度为1 A·g~(-1)时,CuFe_2O_4-20%rGO复合材料经1 000次充放电后的比电容保持率为86.17%。     

Ultrasonic-assisted synthesis of magnetite/carbon nanocomposite for electrochemical supercapacitor

Iron oxides are considered as the promising pseudocapacitive materials for high-performance supercapacitors due to their high theoretical specific capacitance, low cost, environmental benignity, and natural abundance. In this work, we study capacitive behavior of different magnetite (Fe₃O₄) nanoparticles/carbon black (CB) composites ratios. These composites are synthesized by the coprecipitation method in the presence of ultrasonic waves. The structural and morphological characteristics of the magnetite/CB composites are investigated by X-ray diffraction and scanning electron microscopy, respectively. The electrochemical performance of magnetite/CB composite electrodes is tested by cyclic voltammetry and galvanostatic charge/discharge in a Na₂SO₄ electrolyte. The results indicate that the magnetite/CB electrodes show typical pseudo-capacitive behavior in Na₂SO₄ solution. Moreover, in comparison to the pure Fe₃O₄ (37 F g^?1) and carbon black (23 F g^?1), the as-prepared 45 % magnetite/CB nanocomposite electrode shows a higher specific capacitance (300 F g^?1). Additionally, the supercapacitor device of the magnetite/CB nanocomposite exhibits excellent long cycle life along with 98.5 % specific capacitance retained after 10,000 cycle tests.     

Three-dimensional porous reduced graphene oxide decorated with MoS2 quantum dots for electrochemical determination of hydrogen peroxide

Three-dimensional (3D) graphene-based nanomaterials have shown wide applications in electrochemical fields such as biosensors. In this study, we displayed a simple fabrication of 3D structural reduced graphene oxide (3D structural RGO) decorated with molybdenum disulfide quantum dots (MoS₂QDs) through a three-step reaction process. With its abundant raw materials, this strategy is economic and non-toxic. Various characterization techniques were utilized to characterize the morphologies of the synthesized MoS₂QDs, graphene oxide (GO), and 3D structural RGO-MoS₂QDs composites. Simultaneously, X-ray photoelectron spectroscopy was applied to characterize the structure and properties of composites. In order to understand the effects of the reaction period on the structure of 3D structural RGO-MoS₂QDs, a series of samples with various reaction periods were prepared for morphological characterization. Finally, the fabricated 3D structural RGO-MoS₂QDs composites were used to modify a glassy carbon electrode as an electrochemical non-enzymatic hydrogen peroxide (H₂O₂) sensor. The obtained results indicate that the fabricated electrochemical H₂O₂ sensor exhibits a wide detection range (0.01–5.57 mM), low detection limit (1.90 μM), good anti-interference performance, and long-time stability (18 days).     

Enhancing effect of boron trifluoride diethyl etherate electrolytes on capacitance performance of electropolymerized poly[poly(<Emphasis Type="Italic">N</Emphasis>-vinyl-carbazole)] films

In this paper, poly[poly(N-vinyl-carbazole)] (PPVK) films electrodeposited in tetrahydrofuran (THF) containing 12 % boron trifluoride diethyl etherate (BFEE) were studied as electrode active material for supercapacitors. The morphology and thermal property were characterized by SEM, atomic force microscopy (AFM), and thermogravimetry (TG), respectively. The electrochemical capacitive behaviors of the PPVK films were also investigated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The electrochemical results showed that the specific capacitance of PPVK films in CH₃CN solution was about 126 mF cm^?2 at 1.5 mA cm^?2 and the capacitance retention was only 14.4 % after 1000 cycles. It was exciting to improve the specific capacitance up to 169.3 mF cm^?2 at 1.5 mA cm^?2 and to make the cyclic stability increase to 81.8 % capacitance retention after 5000 cycles when the equivalent BFEE was added into the CH₃CN solution containing 0.05 M Bu₄NBF₄ electrolyte. These results clearly demonstrated that BFEE was an efficient promoter for the enhancement of the capacitance performance of PPVK films. Therefore, with the help of BFEE electrolyte, the PPVK films have potential application as capacitive materials in high-performance energy storage devices.     

Synthesis and properties of BaCe1−xYxO3−δ–BaWO4 composite protonic conductors

Barium cerate doped by trivalent rare earth metal ions is a potentially huge component of materials for electrochemical industry due to its high protonic conductivity. However, the poor chemical stability especially in the presence of CO₂, SO₂ or H₂O, resulting in decreasing the mechanical durability of obtained materials, limits their possible applications. The new approach towards stable ceramic protonic conductors with high electrical conductivity is presented. Thermal stability of yttrium doped (10 mol%) of BaCeO₃ was enhanced by forming the composite material BaCe_0.9Y_0.1O₃–BaWO₄ (10 mol% of BaWO₄). The synthesis was performed by solid-state reaction method. The detailed study of thermal decomposition of starting powders mixture was performed using thermogravimetry and differential thermal analysis (TG/DTA) techniques combined with Evolved Gas Analysis (EGA—mass spectrometry). Structure, phase composition and microstructure together with thermal stability of sintered materials were determined. The exposition tests were performed to characterise the stability of composites in carbon dioxide and water vapour-rich atmospheres. The samples were exposed to atmosphere containing CO₂/H₂O (7 % of CO₂ in air, 100 % RH) at temperature of 25 °C for 300 h. Thermal analysis supplied with mass spectrometry was applied to analyse the materials after the test. The results of this experiment showed better chemical resistance of composite material—BaCe_0.9Y_0.1O₃ with 10 mol% of BaWO₄ compared to single phase material.