Electrochemical oxidation of a carbon black loaded polymer electrode in aqueous electrolytes

The suitability of a polymeric composite material for use as part of an anode structure in a cathodic protection system has been examined. The composite material was a conductive blend (volume resistivity typically 1.5 Ω cm) of carbon black in a polyethylene binder. A long operational lifetime for the material demands that the rate of carbon loss must be low. In the work reported here, electrochemical and in situ analytical techniques were employed to characterise the performance of the material over a wide range of anodic current densities in a variety of aqueous electrolytes. The predominant anodic electrochemical reaction on the polymeric material is CO₂ formation in acid and neutral solutions, which causes loss of carbon from the surface and the development of a non-conducting layer of polyethylene. The characteristics of the reaction suggest that it occurs via the discharge of H₂O. In alkaline pH, however, the anodic reactions are more complex. A high OH⁻ concentration (pH 12 or higher) favours the formation of oxygen rather than CO₂, particularly at low anodic potentials. The presence of CO₃ ²⁻ in the electrolyte catalyses the evolution of oxygen at pH values as low as 9. The electrochemical formation of oxygen always occurs in parallel with the generation of some humic acid in the solution. Received: 23 July 1998 / Accepted: 17 November 1998     

能源催化材料的电化学合成

电催化是发展可持续洁净能源技术的基础科学,是电化学能源转换和物质转化的关键环节.精准合成催化活性纳米结构是制约很多电催化反应走向实际应用的重要挑战.与湿化学合成、固相合成和气相沉积等传统方法相比,电化学合成是一种简单、快速、廉价及可控的高效催化材料制备方法,也是一种最为直接的一体化电极制备方法.本文综述了近年来利用电化...     

多阶半微分阴极溶出伏安法测定痕量硒(Ⅳ)的研究

阴极溶出伏安法测定痕量硒已有报导^[1~5],但准确度不佳,灵敏度还嫌不够。本文研究了盐酸和铜体系测定硒,在适宜条件,测定硒的浓度范围为0.04～20ng/mL,检测限为pg/mL级,硒含量在0.14ng/mL,变动系数小于10％。用拟定的方法测定了低硒地区水样及含硒量较高的粮食和人发,均获得了满意结果。     

边界元方法计算牺牲阳极的接水电阻

本文在建立了阴极保护电位场数学模型的基础上，以边界元方法模拟牺牲阳极与低碳钢直接偶合时牺牲阳极的工作状态。     

地下结构物外加电流阴极保护用阳极评述

本文分析了地下结构物外加电流阴极保护用阳极的工况环境条件 ;并对各类阳极材料的性能特点进行了评述 ;探讨了埋地辅助阳极材料的发展与应用方向 .     

有机物的阴极间接电氧化(Ⅱ)——烯酸的阴极间接环氧化

建立一种新的阴极间接电氧化体系 ,以VO(acac) 2 OOH/VO(acac) 2 为氧化还原媒质 ,通过催化阴极由O2 电还原产生的H2 O2 对某些烯酸如顺丁烯二酸、反丁烯二酸和丁烯酸等进行间接环氧化 .研究了 pH值、温度、电流密度等因素对反应的影响 .本文是继前文[1]之后所建立的又一新的氧化还原媒质 .此研究对有机电合成的发展具有重要的理论意义和实际意义 .     

Template-free synthesis of MnO2 nanowires with secondary flower like structure: Characterization and supercapacitor behavior studies

Manganese dioxide (MnO₂) nanowires with diameter about 30-70 nm is achieved via a two-step process: first, template-free cathodic electrodeposition from aqueous solution of Mn(NO₃)₂ on steel substrate and followed by heat treatment. The temperature-annealed sample was studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) methods and Fourier transform infrared (FT-IR) spectroscopy. The electrochemical performance of the MnO₂ sample was studied by cyclic voltammetry (CV) and chronopotentiometry in Na₂SO₄ solutions. The sample showed excellent supercapacitive behavior. The specific capacitance (SC) of 237 F g⁻¹ in a potential window of 0-0.9V was obtained at the scan rate of 2 mV s⁻¹. The SC calculated from the chronopotentiometry data is about 246 F g⁻¹. The SC was decreased by 16% after 1000 cycles.     

Electrochemical Study of Potassium Fluoride in a Cryolite-Aluminum Oxide Molten Salt

Selective and efficient electrochemical methods to characterize aluminum are necessary. Current methods are based on potentiodynamic polarization, recurrent potential double pulses, chronopotentiometry, open-circuit chronopotentiometry, and potentiostatic electrolysis, but have not been used to characterize the deposition of aluminum in Na₃AlF₆-Al₂O₃-KF molten salts. The control processes of the formation of aluminum-tungsten intermetallic compounds, and the deposition of aluminum have been investigated by using steady-state potentiodynamic cathodic polarization curves. The dissolution loss rate of aluminum was determined with an increase in KF concentration by the analysis of recurrent potential double pulses. Using chronopotentiometry, it was confirmed that the deposition potential of aluminum shifted more negative as the KF concentration increased, and a higher KF concentrations induced a higher cathodic overpotential. From open-circuit potential measurements and scanning electron micrographs, it was concluded that aluminum(III) ions react with tungsten substrates to form an aluminum-tungsten compound, and the reaction mechanism of aluminum was determined. These electrochemical methods applied with aluminum electrolysis were accurate, efficient, and reliable.     

Microscale isolation of native forms of lysozyme from chicken egg white by gel isoelectric focusing

To separate and extract the native states of lysozyme from chicken egg white, a hybrid method for the mobilization of proteins after non‐denaturing gel isoelectric focusing (IEF) combined with detection of lysozyme activity was developed. When the proteins in the chicken egg white were first separated using non‐denaturing gel IEF, a lysozyme was obtained at the top of the gel column at the cathode end of the IEF. And, when the IEF‐separated proteins of the egg white were mobilized by replacing the cathodic sodium hydroxide solution with phosphoric acid solution, an additional active state of the lysozyme that could be bound to proteins, such as ovotransferrin, was extracted from the solution. Furthermore, it was shown that the addition of lysozyme, obtained via IEF, to pure ovotransferrin generated a complex manifesting lysozyme activity, clearly indicating a successful reconstruction of the lysozyme‐ovotransferrin complex in vitro. Therefore, the obtained results demonstrated that the native states of lysozymes, such as lysozyme and the lysozyme‐ovotransferrin complex, can be effectively separated and extracted using non‐denaturing gel IEF. Thus, this method can be applied to separate and extract different charge states of native proteins that retain their biological activities.