Study of capacitive properties in supercapacitor for copolymer of aniline with m-phenylenediamine

The copolymers were synthesized with different molar ratios of m-phenylenediamine to aniline (R for short) by a chemical oxidation method. The products were first used as electrochemical activity materials of the supercapacitor. Capacitive behaviors of the prepared copolymers in 1 mol·L⁻¹ H₂SO₄ electrolyte were examined by electrochemical impedance spectroscopy, cyclic voltammeter, and galvanostatic charge/discharge. The relationship of molar ratios with capacitive property of the prepared products was investigated too. The results showed that the product with R of 2:98 displayed better electrochemical properties than that of the other products. Compared with the synthesized polymer in the absence of m-phenylenediamine, the polymerized copolymer with R of 2:98 exhibited the initial specific capacitance value of 475 F·g⁻¹, which increased by nearly 10.1% than that of the former at a current density of 200 mA·g⁻¹ in 1 mol·L⁻¹ H₂SO₄ electrolyte in the potential range of −0.3 to 0.7 V. The discharge specific capacitance value of the copolymer remained 300 F·g⁻¹ after 1,000 cycles, exhibiting a good cycling performance and the structure stability.     

苯胺的电化学聚合计时电流方程式

本文提出了苯胺的电化学聚合计时电流方程式, 并进行了验证。浓度为1.10mol.dm^-^3苯胺(内含2.2mol.dm^-^3HCl)溶液在铂圆盘电极上进行电化学聚合反应, 理论与实验相符。     

Electrodeposition of polyaniline in long TiO2 nanotube arrays for high-areal capacitance supercapacitor electrodes

Journal of Solid State Electrochemistry - Anodic TiO2 nanotube arrays (TNTAs) were found to be a suitable scaffold for the loading of other active materials for supercapacitors. The prepared...     

Electrochemical polymerization of aniline in SDS admicelles

The electrochemical polymerization of aniline was studied in sodium dodecyl sulfate (SDS) admicelles. The results demonstrate that electrochemical polymerization of aniline can be catalyzed by admicelles. The catalytic efficiency in SDS solutions increased slowly with SDS concentration when the SDS concentration was very low, but increased rapidly when SDS admicelles formed on the electrode surface. The catalytic efficiency decreased with the addition of n-pentanol. The polyaniline films formed in SDS admicelles were nanometer films and the size of particles in the films increased with SDS concentration, but decreased with the addition of n-pentanol. Therefore, n-C₅H₁₁OH can be used to regulate the electrochemical polymerization of aniline in SDS admicelles.     

Electrochemical polymerization of aniline in phosphoric acid

The electrochemical synthesis of common conductive polymers such as polyaniline in phosphoric acid is a little different from that in other acidic media such as sulfuric acid. Electropolymerization in phosphoric acid is difficult, and this electrolyte medium is not applicable for this purpose. However, it is possible to overcome this problem by the addition of a small amount of sulfuric acid. In this case, the electropolymerization process can be successfully performed when the phosphate ion is doped. For instance, polyaniline films electrodeposited from an electrolyte solution of phosphoric acid have good stabilities and useful morphologies. Interestingly, phosphate doping results in the formation of nanostructures, whereas the polymer surface is macroscopically smooth. In an appropriate ratio, a mixed electrolyte of H₃PO₄ and H₂SO₄ can be used for the electropolymerization of aniline; thus, H₂SO₄ acts as a required agent for successful polymer growth, and H₃PO₄ acts as a doping agent. In this case, a small amount of sulfate is incorporated into the polymer matrix, which does not participate in the electrochemical insertion/extraction process. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3304–3311, 2006     

Optimization of polymerization conditions of furan with aniline for variable conducting polymers

A high-throughput multiparameter optimization of chemical oxidative polymerization conditions has been developed for a facile synthesis of furan homopolymers and furan/aniline copolymers using a combinatorial method. The polymerization yield, molecular structure, and properties of the polymers would be optimized against typical polymerization parameters, including oxidant species, medium species, temperature, oxidant/monomer ratio, monomer concentration, dopant concentration, and furan/aniline comonomer ratio. The electrical conductivity, lead ion adsorptivity, chemical resistance, and thermal behavior of the polymers were also elaborated. It is found that only a combination of FeCl(3) and nitromethane as oxidant and medium, respectively, is appropriate for the furan homopolymerization. The homopolymerization yield increases consistently with an increase in the monomer concentration from 0.05 to 0.2 M and the FeCl(3)/furan molar ratio from 0.25 to 1.25. Although the as-prepared polyfuran exhibits very low conductivity, down to 10(-11) S cm(-1), the HCl- and HClO(4)-doped polyfurans possess much higher conductivities of 9.2 x 10(-8) and 2.38 x 10(-5) S cm(-1), respectively. In addition, the conductivity of the furan/aniline copolymer rises steadily with increasing aniline content, although the copolymerization yield shows a minimum at the furan/aniline molar ratio of 60/40, which is evidence of the occurrence of a real copolymerization between the furan and aniline monomers. The difficulty of synthesizing conducting polyfuran could be overcome to some extent by the polymerization in an appropriate condition optimized in this study. Particularly, the difficulty of synthesizing poly(furan-co-aniline) having much higher conductivity than the polyfuran would be largely conquered by chemical oxidative copolymerization of furan with aniline.     

In situ polymerization of aniline in electrospun microfbers简

Conductive microfibers with an average diameter of ca. 1.0 mm were prepared by in situ polymerization of aniline, in which poly(vinylchloride-acrylonitrile)(PVC-AN) was used as the filament-material in electrospinning to form precursor microfibers and carry the aniline monomers. Fourier-transform infrared(FTIR) results demonstrated that PANi was successfully polymerized in the microfibers. The morphology of the PVC-AN-PANi microfibers was observed by scanning electron microscopy(SEM). Results of differential scanning calorimetry indicated that the polymer composite of PVC-AN-PANi formed via molecular interactions. Although the conductivity of PVC-AN-PANi microfibers was still limited(2.2 fi 10à8S/cm), this method provided an effective and convenient approach for preparing highly uniform and soft microfibrous electrodes.     

Effect of hexamethylenetetramines (HMT) surfactant concentration on the performance of TiO2 nanostructure photoelectrochemical cells

Hexamethylenetetramine (HMT) surfactant was used to modify the morphology of TiO₂ thin film nanostructure prepared by a simple technique, namely, liquid phase deposition (LPD) during its growth process. In order to obtain various surface morphologies of TiO₂ nanostructures, the concentration of HMT was varied from 10 to 100 mM. It was found that with an increase in concentration of HMT, the morphology of TiO₂ nanorod in term of its grain size decreases due to the particles agglomeration grown on the surface. The TiO₂ nanostructures with various grain sizes were utilized as photovoltaic materials in photoelectrochemical cell measurement. The highest performance of the cell in terms of the short-circuit current density, J _sc was 0.069 mA cm^?2. This result was achieved from the TiO₂ nanorod cell with the smallest grain size, 12 ± 2 nm. The J _sc of the cell increased with concentration of HMT. The cell utilizing the TiO₂ nanostructure with the smallest grain size possessed the best interfacial contact at the TiO₂/electrolyte containing iodide/triiodide redox couple. Thus, the redox reaction was optimised at this interface.     

Ellipsoidal TiO2 hierarchitectures with enhanced photovoltaic performance

Hierarchical TiO(2) ellipsoids 250-500 nm in size have been synthesized on a large scale by a template-free hydrothermal route. The submicrometer-sized hierarchitectures are assembled from highly crystallized anatase nanorods about 17 nm in diameter with macroporous cavities on the outer shells. Based on the time-dependent morphological evolution under hydrothermal conditions, an oriented attachment process is proposed to explain formation of the hierarchical structures. Such hierarchical TiO(2) not only adsorbs large amounts of dye molecules due to high surface area, but also shows good light scattering caused by the submicrometer size. The TiO(2) hierarchitectures were deposited on top of a transparent TiO(2) nanocrystalline main layer to construct a double-layered photoanode for dye-sensitized solar cell (DSC) application, exhibiting enhanced light harvesting and power-conversion efficiency compared to a commercial TiO(2)-based electrode.     

PPy modified titanium foam electrode with high performance for supercapacitor

Pyrrole was polymerized on the surface of titanium foam using FeCl₃ as oxidant and the as-synthesized product could be directly used as electrode for supercapacitor. The globular polypyrrole (PPy) particles were firmly loaded on the substrate with high density. The morphology study of PPy film is observed in SEM images, the XRD, FTIR and UV–vis spectra reveal the structure and crystalline of PPy nanoparticles. The electrochemical properties of PPy modified electrode are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and cycle life techniques. The electrochemical measurements showed such a PPy–Ti electrode had a wide working potential window, a high specific capacitance of 855 F g⁻¹ and excellent cycle stability at a discharge current density of 1 A g⁻¹.     

CeO2 nanoparticles/graphene nanocomposite-based high performance supercapacitor

CeO(2) nanoparticles/graphene nanocomposite is fabricated by depositing CeO(2) nanoparticles onto three-dimensional graphene material and its supercapacitor performance is further investigated. The nanocomposite shows a high specific capacitance and power density, demonstrating a strong synergistic effect possibly contributed from improved conductivity of CeO(2) and better utilization of graphene.     

Anionic surfactant for silica-coated polystyrene composite microspheres prepared with miniemulsion polymerization

Raspberry-like composite microspheres with polystyrene (PS) cores and silica shell were prepared through miniemulsion polymerization by using the anionic sodium dodecyl sulfate (SDS) as a surfactant and 1-vinylimidazole (1-VID) as an auxiliary monomer. The strong acid–base interaction between acidic hydroxyl groups of silica surfaces and basic amino groups of 1-VID promote the formation of long-term stable PS/SiO₂ nanocomposite microspheres. Transmission electron microscopy TEM studies indicated that the acid–base interaction between silica nanoparticles and auxiliary monomer was strong enough for the formation of colloidally stable composite microspheres, which have raspberry-like morphology. Influences of several synthetic parameters, such as initial silica amount, the amount of auxiliary monomer 1-VID, and SDS concentration on the polymerization stability, diameters, and morphology of the composite microspheres were studied. A tentative mechanism of the formation of nanocomposite particles was proposed.     

超级电容器电极材料MnO_2纳米棒的制备及其电化学性能(英文)

以洋葱碳为还原剂,KMnO4为氧化剂,稀硫酸溶液为溶剂,采用水热法一步制备MnO2纳米棒.利用X射线衍射仪和透射电子显微镜分析了MnO2纳米棒的物相、结构、形貌;将MnO2纳米棒作为电极材料组装了超级电容器,采用电池测试系统测定了超级电容器的电化学性能.结果表明,所得到的产物为α-MnO2,其直径为5~10nm,长度为50~100nm;以MnO2纳米棒作为电极材料组装的超级电容器具有较高的比容量和稳定性,有望在超级电容器的研究和应用中得到推广.     

Interaction of a cationic surfactant to sodium polyphosphates with different degrees of polymerization

 The binding behavior of dodecylpyridinium chloride to sodium polyphosphate of various degrees of polymerization (DP) was studied by means of a potentiometric titration method using a surfactant-selective electrode in the presence of 10 mM NaCl at 30 °C. Binding isotherms were analyzed by direct calculation of a matrix expressing the partition function. It is found that binding affinity depends prominently on the polymer chainlength when the DP value is less than ca. 35, but becomes nearly independent on DP thereafter. No binding was observed for linear triphosphate or cyclic trimetaphosphate anions. The picture that arises for the binding is that the polymer’s end-effect reduces the apparent cooperativity, while the hydrophobic interaction with neighboring surfactant remains constant because of the short-range nature of the interaction. The so-called end-effect is associated with a superimposition of electrostatic potentials around the polymer rods. Both the matrix method and the Satake–Yang equation were carried out for simulations, and the matrix one shows a better fitting with the experimental data for the short-chain polyelectrolyte. Received: 1 July 1997 Accepted: 21 August 1997     

Miniemulsion polymerization of styrene with a block copolymer surfactant

A series of miniemulsion systems based on styrene/azobisisobutyronitrile in the presence of poly(methyl methacrylate‐b‐2‐(dimethylamino)ethyl methacrylate) as a surfactant and hexadecane (HD) as a cosurfactant were developed. For comparison, a series of pseudoconventional emulsions also were carried out with the same procedure used for the aforementioned series but without the cosurfactant (HD). Both the droplet size and shelf life were also measured. Experimental results indicate that it is possible to slow the effect of Ostwald ripening and thereby produce a stable miniemulsion with the block copolymer as the surfactant and HD as the cosurfactant. In addition, the extent to which varying the surfactant concentration and copolymer composition could affect both the polymer particle size during the polymerization and the polymerization rate was examined. Variation in the polymer particle sizes during polymerization indicates that droplet and aqueous (micellar or both homogeneous) nucleation occurs in the miniemulsion polymerization. With the same concentration of the surfactant used in the miniemulsion polymerization, the polymerization rates of systems with M₁₂B₃₆ are faster than those of systems with M₁₂B₁₂. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1818–1827, 2000     

A study of the mechanism of aniline polymerization

A chemical polymerization of aniline is quenched at specific reaction time intervals and the amounts of unreacted aniline and formed p-aminodiphenylamine is observed. Oxidation of aniline to generate p-aminodiphenylamine is observed. Oxidation of aniline to generate p-aminodiphenylamine is the slow step in the plymerization. Furthermore, the tetramer of aniline is used as starting material for polymerization under the same conditions as polymerization of aniline. Direct coupling of two tetramers leading to polymer is not observed. A mechanism of polymerization of aniline is proposed     

Surface-treated TiO2 nanoparticles for dye-sensitized solar cells with remarkably enhanced performance

Dye-sensitized solar cells (DSSCs) were prepared by capitalizing on mesoporous P-25 TiO(2) nanoparticle film sensitized with N719 dyes. Subjecting TiO(2) nanoparticle films to TiCl(4) treatment, the device performance was improved. More importantly, O(2) plasma processing of TiO(2) film that was not previously TiCl(4)-treated resulted in a lower efficiency; by contrast, subsequent O(2) plasma exposure after TiCl(4) treatment markedly enhanced the power conversion efficiency, PCE, of DSSCs. Remarkably, with TiCl(4) and O(2) plasma treatments dye-sensitized TiO(2) nanoparticle solar cells produced with 21 μm thick TiO(2) film illuminated under 100 mW/cm(2) exhibited a PCE as high as 8.35%, twice of untreated cells of 3.86%.     

阳离子表面活性剂体系中纳米TiO2的合成及表征

在阳离子表面活性剂双十八烷基二甲基氯化铵(D1821)的水溶液中,以钛酸四丁酯为钛源,在室温下合成了具有日光催化性能的纳米TiO2,考察了合成条件(反应温度、pH值、焙烧温度)对产物结构的影响。通过x射线衍射、透射电镜对所合成的样品进行表征,并对非离子表面活性剂壬基酚聚氧乙烯醚(NPE-10)进行了光催化降解性能研究。结果表明:反应温度为20℃,pH=7,焙烧温度为500℃时所合成的样品颗粒分散均匀,晶型完整,而且形成了锐钛矿和金红石的混晶结构。日光照射下,这种纳米TiO2对NPE-10表现出了较好的光催化性能,3h的降解率达到了80%。     

Electrochemical polymerization of aniline inside ordered macroporous carbon

3D ordered macroporous multicomponent composite materials have been fabricated by electrochemical deposition of aniline on the inner surface of macroporous carbon; the maximum thickness of polyaniline (PANI) deposited is dependent on the concentration of the aniline as well as the dimension of the windows in the macroporous carbon.     

Synthesis of sponge-like TiO2 with surface-phase junctions for enhanced visible-light photocatalytic performance

Maximizing adsorption and catalytic active sites and promoting the photo-excited charge separation are two key factors to achieve excellent photocatalytic performance. In this study, we report a sol-gel synthesis approach to obtain non-metal doped TiO₂ with sponge-like structure and surface-phase junctions all at once. While doping of carbon and nitrogen shifted the activation wavelength to the visible-light region, the innovative use of perchloric acid as a pore-making agent led to the formation of three-dimensional lamellar and porous structure with surface-phase junctions. High surface area with catalytic active sites rendered by the sponge-like structure and surface-phase junctions contributed to the much improved photocatalytic degradation efficiency toward rhodamine B, tetracycline and Disperse Red 60 with excellent reusability and stability. The improved generation and separation efficiency of the photo-induced charge carriers of the as-prepared TiO₂ were supported by electrochemical impedance measurements and transient photocurrent responses. This method could also be applied to other photocatalysts to achieve structural alteration and element doping simultaneously.