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2.
The electrochemical stability of polycrystalline thin film MoxN (x=1 and 2) electrodes deposited on previously nitrided polycrystalline Ti and bare Ti substrates and exposed to 4.4m H2SO4 electrolyte has been investigated. The electrodes were prepared by a temperature programmed procedure involving the reaction of MoO3 films and NH3. Cyclic voltammetry and a.c. impedance spectroscopy indicated that the range of electrochemical voltage stability in the electrolyte of the MoxN films on nitrided Ti substrates, referenced to a standard hydrogen electrode to be –0.01 to+0.69V. These electrodes had a calculated capacitance of about 315Fcm–3. The MoxN films on Ti substrates were electrochemically stable from –0.01 to +0.67V; however, they contained unconverted MoO2 which acted to reduce the calculated capacitance to about 210Fcm–3. At and above +0.70V and +0.68V on nitrided Ti and Ti substrates, respectively, an electrochemical reaction occurred. The formation of an amorphous phase in the reacted MoxN films was indicated by X-ray diffraction (XRD). Secondary ion mass spectroscopy (SIMS) showed increases in the atomic concentrations of hydrogen, oxygen and sulfur in the reacted films. The voltage bias applied to the electrodes influenced the chemical composition of the reacted films. 相似文献
3.
Yuehua Wen Jie Cheng Gaoping Cao Yusheng Yang 《Journal of Applied Electrochemistry》2007,37(5):543-548
For double-layer capacitors in alkaline electrolyte, the specific capacitance of the positive electrode is not equal to that
of the negative one. Thus, capacitor performance cannot be optimal with a positive/negative electrode matching ratio of 1.
In this study nanoporous glassy carbons (NPGCs) were employed as the electrodes of capacitors, and the influence of matching
ratio between positive and negative electrode on capacitor performance was systematically investigated. In aqueous KOH, the
specific capacitance of the positive electrode is lower than that of the negative electrode. The matching ratio at which a
maximum capacitance is obtained is dependent on the values of the positive and negative electrode capacitance. At low current
rate, the highest specific capacitance is achieved at a matching ratio slightly higher than 1. At high current rate, a capacitor
has the highest specific capacitance with the lowest resistance at a matching ratio of 1.5. This indicates that an optimum
matching relationship between positive and negative electrodes is attained. 相似文献
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功能水凝胶作为一种三维高分子网络结构的软湿材料,具有可灵活调控的功能特性,为设计和构建高性能柔性超级电容器提供了理想的材料。本文综述了近年来面向柔性超级电容器领域的功能水凝胶材料的研究进展,重点分类介绍了面向电化学双层电容器和赝电容器的功能水凝胶材料的设计构建和性能强化。探讨了通过水凝胶电解质及电极材料的组成结构设计和性能调控来提升超级电容器的电化学性能和力学性能的策略。同时,探讨了水凝胶电解质及电极材料的组成结构设计和性能调控在实现其自愈合、高耐寒等多样化功能特性方面的重要作用。最后,对功能水凝胶材料柔性超级电容器在高储能、高柔性、高保水、自愈合、高耐寒、绿色可降解等方面的未来发展进行了展望。 相似文献
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Hae‐Jun Seok Jae‐Hoon Lee Jin‐Hyeok Park Sang‐Hwi Lim Han‐Ki Kim 《Israel journal of chemistry》2019,59(8):729-746
In this review, we briefly describe a recent research development of transparent conducting electrodes (TCEs) for next‐generation quantum dot‐based light‐emitting diodes (QDLEDs). Although sputtered Sn‐doped In2O3 (ITO) and chemically grown F‐doped SnO2 (FTO) electrodes have mainly been employed as transparent electrodes for QDLEDs, there have been great advances in TCE materials and fabrication processes. This review presents important characteristics of various TCE and applications in QDLEDs as a transparent cathode or anode. In particular, we will focus on characteristics of metal grids, metal nanowire, carbon nanotube, graphene, and hybrid electrodes for QDLEDs as promising alternatives to typical ITO and FTO electrodes. In addition, we discuss the current status of transparent conducting oxide‐based QDLEDs. By comparing the performances of QDLED with different TCEs, we suggest promising alternatives ITO or FTO electrodes. 相似文献
7.
淀粉模板法辅助合成二氧化锰纳米棒及其电容特性研究 总被引：2，自引：0，他引：2
以淀粉为模板,结合浸渍-煅烧法合成了MnO2纳米棒,对产物晶型结构、形貌大小和电容特性等进行表征。测试结果表明所得样品为α-MnO2纳米棒,其平均直径为20 nm左右,平均长度约为75 nm。在1.0 mol/L的Na2SO4电解液中,01.0V电位区间内,充放电电流为2.0、5.0、10.0 mA时,所制备的α-MnO2放电比电容分别达到了186、120、90 F/g。2 mA恒流充放电1 000次后,MnO2的放电比容量保持率为91%。 相似文献
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In this work, we demonstrate a simple method to modify indium tin oxide (ITO) electrodes in order to perform electro-catalytic oxidation of alcohols in alkaline medium. Metal hexacyanoferrate (MHCF) films such as nickel hexacyanoferrate (NiHCF) and copper hexacyanoferrate (CuHCF) were successfully immobilized on ITO electrodes using an electrochemical method. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the structural and morphological aspects of MHCF films. Cyclic voltammetry (CV) was used to study the redox properties and to determine the surface coverage of these films on ITO electrodes. Electrochemical potential cycling was carried out in alkaline medium in order to alter the chemical structure of these films and convert to their corresponding metal hydroxide films. SEM and XPS were performed to analyze the structure and morphology of metal hydroxide modified electrodes. Electro-catalytic oxidation ability of these films towards methanol and ethanol in alkaline medium was investigated using CV. From these studies we found that metal hydroxide modified electrodes show a better catalytic performance and good stability for methanol oxidation along with the alleviation of CO poisoning effect. We have obtained an anodic oxidation current density of ∼82 mA cm−2 for methanol oxidation, which is at least 10 fold higher than that of any metal hydroxide modified electrodes reported till date. The onset potential for methanol oxidation is lowered by ∼200 mV compared to other chemically modified electrodes reported. A plausible mechanism was proposed for the alcohol oxidation based on the redox properties of these modified electrodes. The methodology adapted in this work does not contain costlier noble metals like platinum and ruthenium and is economically viable. 相似文献
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水系锌离子电池（ZIBs）在安全性和规模化生产应用方面具有广阔的前景,但正极和负极的能量密度和循环寿命较低阻碍了ZIBs的实际应用。而以纺织材料为基材的电极具有高导电性、化学稳定性和易与其他活性物质负载的特点,能有效解决上述问题。该文以纺织视角阐述现阶段纺织类柔性锌离子电池的研究进展,以纤维状锌离子电池和平面结构型锌离子电池两个维度对柔性锌离子电池进行总结,明确两种类型柔性锌离子电池正极材料的反应动力学与电极结构、表面特性及活性材料复合条件的构效关系。最后,针对纺织基锌离子电池发展存在的问题进行说明,并对未来需要攻克的重点难点进行分析及展望。 相似文献
11.
Water self‐diffusion coefficients and longitudinal relaxation rates in sodium polyacrylate solutions and gels were measured by NMR, as a function of polymer content and structure in a physiological concentration range of monovalent and divalent cations, Ca2+ and Na+. Several physical models describing the self‐diffusion of the solvent were applied and compared. A free‐volume model was found to be in good agreement with the experimental results over a wide range of polymer concentrations. The longitudinal relaxation rate exhibited linear dependence on polymer concentration below a critical concentration and showed non‐linear behavior at higher concentrations. Both the water self‐diffusion and relaxation were less influenced by the polymer in the gel state than in the uncrosslinked polymer solutions. The effect of Na+ on the mobility of water molecules was practically undetectable. In contrast, addition of Ca2+ strongly increased the longitudinal relaxation rate while its effect on the self‐diffusion coefficient was much less pronounced. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40001. 相似文献
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On the basis of sol–gel methodology, a novel degradable hybrid electrolyte, poly(lactic acid) (PLA)/poly(methyl methacrylate) (PMMA)/silicon dioxide (SiO2) hybrid electrolyte, was prepared from PLA, methyl methacrylate, and tetraethoxylsilicon with 3‐methacryloxypropyl trimethoxysilane as a coupling agent. As observed from Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy spectra, the PLA, PMMA, and silica units were linked by covalent bonds through the coupling agent in a hybrid network. Differential scanning calorimetry results show that the heat‐resistance properties of the hybrid electrolyte improved with increasing SiO2 content. The hybrid electrolyte was shown to be amorphous by the X‐ray diffraction results. From study of ionic conductivity by alternating‐current impedance, the ionic conductivity of the PLA/PMMA/SiO2 hybrid electrolyte increased with increasing silica content, reached a maximum value of 2.42 × 10?4 S/cm at 2 wt % SiO2, and then decreased. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
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Monomethoxy poly(ethylene glycol) acrylate (MPEGA) was synthesized through the esterification reaction of acrylic acid and methoxy poly(ethylene glycol)s (MPEGs) of different molecular weights. Then, MPEGA was copolymerized with methyl methacrylate, butyl acrylate, and β‐carboxyethyl acrylate neutralized with potassium hydroxide via conventional solution polymerization. In this way, a single‐ion conductive polymer‐electrolyte‐based antistatic agent (PEAA), in which potassium (K) ions were used as charge carriers, was obtained. The molecular structure, coordination effects between ether oxygen (EO) groups and K cations, ionic conductivity, and crystallization ability of the copolymer were characterized with Fourier transform infrared, conductivity measurements, polarizing optical microscopy, and differential scanning calorimetry, respectively. The crystallinity of the synthesized PEAA apparently decreased with the molecular weight of MPEG and the EO/K molar ratio decreasing, and this led to a corresponding enhancement of the conductivity. The dependence of the conductivity of the copolymer on temperature could be divided into different linear parts, and each was in good agreement with the Arrhenius equation. Moreover, the dependence of the conductivity on the relative humidity (RH) revealed that the PEAA could maintain high ionic conductivity (∼10−6 S/cm) even at the low RH of 10%. This implies the potential widespread application of PEAAs for the preparation of antistatic composites and especially poly(vinyl chloride)‐ and poly(methyl methacrylate)‐related composites because of their considerable miscibility. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
14.
Luminita‐Ioana Buruiana Ecaterina Avram Adriana Popa Iuliana Stoica Silvia Ioan 《应用聚合物科学杂志》2013,129(4):1752-1762
A new quaternized polysulfone with triphenylphosphonium pendant groups was synthesized by reacting chloromethylated polysulfone with triphenylphosphine. The molecular restructurations, generated by hydrogen bonding, electrostatic interactions, and association phenomena in ternary quaternized polysulfone/N,N‐dimethylformamide (solvent)/water (nonsolvent) systems, were evaluated by rheological investigations. The polyelectrolyte effect, induced by enhanced dissociation of the ionizable groups and by mixed solvents' quality, modify the rheological functions, that is, dynamic viscosity, elastic shear modulus, and viscous shear modulus, as well as the thermodynamic parameters obtained from the rheological properties, such as apparent activation energy. These results were correlated with the morphological properties of the films obtained from solutions in solvent/nonsolvent mixtures and compared with other quaternized polysulfones, having different hydrophobic characteristics. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
15.
Stephen Johnson Julieta Trejo Masoumeh Veisi G. Paul Willhite Jenn‐Tai Liang Cory Berkland 《应用聚合物科学杂志》2010,115(2):1008-1014
Polyacrylamide crosslinked with Cr(III) is a common blocking agent that is injected into oil reservoirs to shut off the water flow to features such as fractures and high‐permeability rock to improve the volumetric sweep efficiency during water flooding. This technique is limited to situations where enough gelant can be injected to fill the high‐permeability zones before gelation occurs. Cr(III) may be encapsulated with a high entrapment efficiency in self‐assembling polyelectrolyte complex nanoparticles with effective diameters of about 100–200 nm and formed by the mixture of polyethylenimine and dextran sulfate in nonstoichiometric amounts. The electrostatic interaction between the polyelectrolytes and the Cr(III) is reversible, but diffusion out of the nanoparticles is retarded, and this results in a delay in gelation from minutes or hours to several days in deionized water. Produced and injection waters often contain salts at concentrations comparable to seawater. The effects of these salts were investigated, and we found that the delay in gelation was further extended to as much as 35 days at 40°C and 35 h at 80°C in the presence of divalent ions at seawater concentrations, either alone or in a field brine or seawater; this greatly increases their potential utility. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
16.
The viscosity as a function of concentration for xanthan gum in both salt‐free solution and in 50 mM NaCl is measured and compared with a scaling theory for polyelectrolytes. In general, the zero shear rate viscosity and the degree of shear thinning increase with polymer concentration. In addition, shear thinning was observed in the dilute regime in both solvents. In salt‐free solution, four concentration regimes of viscosity scaling and three associated critical concentrations were observed (c* ≈ 70 ppm, ce ≈ 400 ppm, and cD ≈ 2000 ppm). In salt solution, only three concentration regimes and two critical concentrations were observed (c* ≈ 200 ppm and ce ≈ 800 ppm). In the presence of salt, the polymer chain structure collapses and occupies much less space resulting in higher values of the critical concentrations. The observed viscosity‐concentration scaling is in very good agreement with theory in the semidilute unentangled and semidilute entangled regimes in both salt‐free and 50 mM NaCl solution. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
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Crosslinked chitosan membranes were prepared with a relatively low degree of crosslinking with epichlorohydrin and glutaraldehyde as crosslinking agents under heterogeneous and homogeneous conditions, respectively. The tensile properties, crystallinity, swelling index, and ionic conductivity of the crosslinked membranes were investigated. A significant decrease in the crystallinity and a large change in the swelling ratio of the crosslinked membrane were observed. In comparison with the uncrosslinked chitosan membrane, when the chitosan membrane was crosslinked with an appropriate degree of crosslinking under homogeneous conditions, its ionic conductivity after hydration for 1 h at room temperature increased by about one order of magnitude. In addition, with a lower concentration of the crosslinking agent, the tensile strength and breaking elongation of the crosslinked membrane were almost unchanged. Moreover, up to a critical value, the tensile strength of the membrane increased gradually, and the breaking elongation decreased slowly. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 306–317, 2003 相似文献
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In this study, polymer–clay nanocomposites (PCNs) composed of poly(vinyl alcohol)s (PVAs), poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid), and fullers earth were prepared by the effective dispersal of inorganic nanoclays in the organic PVA matrix via in situ free‐radical polymerization with potassium persulfate as an initiator and N,N‐methylene bisacrylamide as a crosslinker. The monomer, 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid, was grafted onto the PVA backbone, and at the same time, fullers earth layers were intercalated and exfoliated into the grafted copolymer, especially at a low or moderate loading of the fullers earth. The synthesized PCN materials were characterized by Fourier transform infrared spectroscopy and wide‐angle X‐ray diffraction techniques. The morphological features of the synthesized materials were studied by scanning electron microscopy; this revealed that the swelling ratio of this nanocomposite increased with increasing fullers earth content. The X‐ray diffraction results indicated that the fullers earth was exfoliated in the nanocomposite matrix, and its introduction into the polymer matrix enhanced the percentage crystallinity of the polymer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
19.
By complete reduction of polyamide-6, poly(iminohexamethylene) (PIH) was obtained. This new linear polyamine was characterized by i.r. and by n.m.r. spectroscopy as well as by titration. Differential scanning calorimetry measurements and X-ray diffraction found a high degree of crystallinity whose extent strongly depends upon the pre-treatment. The polyammonium salts that form with inorganic and organic acids show the typical polyelectrolyte effect in viscometry. PIH was alkylated with methyl iodide or acrylic acid and was acylated with N-BOC-l-α-amino acids or N-BOC-ω-amino-alkylenecarboxylic acids. The properties of these derivatives are described. 相似文献
20.
Ion‐exchange membranes were prepared with semi‐interpenetrating networks (s‐IPNs) by mixing a film‐forming polymer, poly(vinyl alcohol) (PVA), for the crosslinked matrix and a polyelectrolyte for the specific ion‐exchange property. Poly(sodium styrenesulfonate) (PSSNa), poly(styrenesulfonic acid) (PSSH), and poly(acrylic acid) (PAA) were used as anionic polyelectrolytes. Polyethyleneimine (PEI), poly(1,1‐dimethyl‐3,5‐dimethylenepiperidinium chloride) (PDDPCl), and poly(diallyldimethylammonium chloride) (PDDMACl) were used as cationic polyelectrolytes. Membranes with PVA 60% and polyelectrolyte 40% showed the best compromise among mechanical, homogeneous, and ion‐exchange properties. Gaseous dibromoethane was used as a crosslinking agent to form the PVA network and for efficient entrapment of the polyelectrolyte in the membrane. The crosslinking time (tc) was optimized for each type of membrane and its influence was studied by thermogravimetric analysis of the sample and scanning electron microscopy observations. The best results (large ion‐exchange capacity and small swelling ratio) were obtained for PVA/PAA and PVA/PSSNa/PSSH membranes. Among anion‐exchange membranes, PVA/PEI gave the best permselectivity (low co‐ion leakage) and the highest ion‐exchange capacity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1572–1580, 2002; DOI 10.1002/app.10420 相似文献
