Electrochemical Behavior of Crystal Violet on Glassy Carbon Electrodes

The electrochemical behavior of Crystal Violet (CV) on the surface of a glassy carbon electrode in potassium chloride, nitrate, and iodide supporting electrolytes was studied using stripping voltammetry. It was demonstrated that an electroactive complex of CV with iodine was adsorbed on the electrode in a KI solution. This property can be used for determining iodide by adsorption–stripping voltammetry.     

Effect of Surface Structure on Behavior of RuO2 Electrodes in Sulfuric Acid Aqueous Solution

The electrochemical properties of RuO₂ electrodes are studied by means of cyclic voltammetry, potential step, and impedance measurements in aqueous 0.5 mol/dm³ H₂SO₄ as a supporting electrolyte solution and applying the hanging electrolyte meniscus technique. Two types of the electrodes are used: bulk as-grown single-crystal having (101) exposed interface and 500 nm film produced by reactive RF magnetron sputtering at 450°C. The surface structure of the RuO₂ electrodes prepared by different techniques is defined from X-ray LAUE backscattering. Experimental data show that, for both RuO₂ electrodes, the charging components include a slow diffusion-controlled contribution, due to proton injection–ejection. The diffusion characteristics and the diffusion coefficients for the same electrodes are estimated and reported.     

2-硝基丙烷在硫酸介质中的电化学还原

2-硝基丙烷在硫酸介质中的电化学还原;硝基丙烷;N-异丙基羟胺;电化学还原     

苯甲酸在疏水性复合电极上的电化学还原行为

以铜片和锌片为基材,复合电镀制得Cu-PTFE(聚四氟乙烯)和Zn-PTFE疏水性复合电极,并将复合电极应用于苯甲酸的电化学还原行为研究。测定了复合电极在电解液中的Tafel极化曲线、循环伏安、电极稳定性和交流阻抗等电化学参数。结果表明,在苯甲酸电还原制备苯甲醛中,Cu-PTFE复合电极相对于Zn-PTFE复合电极具有较高的催化活性,其电还原产率分别为88.4%和79.2%,因此,Cu-PTFE复合电极有望成为苯甲酸电化学还原制备苯甲醛的电极材料。电化学行为的研究结果显示,苯甲酸在疏水性复合电极上的电还原过程可能只受电子迁移过程控制。     

Interfacial Behavior of Cysteine between Mild Steel and Sulfuric Acid as Corrosion Inhibitor

Interfacial behavior of cysteine (Cys) between mild steel and sulfuric acid solution as a corrosion inhibitor has been studied with electrochemical AC (alternating current) and DC (direct current) techniques at (25.0±0.1) °C. The AC impedance results were evaluated using equivalent circuits in which a constant phase element (CPE) has been replaced with double layer capacitance (C_dl) to represent the frequency distribution of experimental data. Changes in impedance parameters (charge transfer resistance and double layer capacitance) indicated that cysteine molecules acted by accumulating at the metal/solution interface. The fractional coverage of the metal surface () was determined using AC impedance results and it was found that the adsorption of cysteine on the mild steel surface followed a Langmuir isotherm model with a standard free energy of adsorption (ΔG⁰_ads) of −35.1 kJ·mol⁻¹.To clarify the type of interaction between mild steel surface and cysteine molecules with a molecular orbital approach, electronic properties, such as, the highest occupied molecular orbital (HOMO) energy, the lowest unoccupied molecular orbital (LUMO) energy, and the frontier molecular orbital coefficients have been calculated. Energy gaps for the interaction of mild steel surface and cysteine molecules (E_{LUMO Fe}−E_{HOMO Cys} and E_{LUMO Cys}−E_{HOMO Fe}) were used to determine whether cysteine molecules acted as electron donors or electron acceptors when they interacted with the mild steel surface. The local reactivity was evaluated through the condensed Fukui indices. Theoretical calculations were carried out using the density functional theory (DFT) at B3LYP level with the 6-311++G(d,p) basis set for all atoms by Gaussian 03W program.     

半胱氨酸在碳钢与硫酸界面的缓蚀行为

Interfacial behavior of cysteine (Cys) between mild steel and sulfuric acid solution as a corrosion inhibitor has been studied with electrochemical AC (alternating current) and DC (direct current) techniques at (25.0±0.1) ℃. The AC impedance results were evaluated using equivalent circuits in which a constant phase element (CPE) has been replaced with double layer capacitance (Cdl) to represent the frequency distribution of experimental data. Changes in impedance parameters (charge transfer resistance and double layer capacitance) indicated that cysteine molecules acted by accumulating at the metal/solution interface. The fractional coverage of the metal surface (θ) was determined using AC impedance results and it was found that the adsorption of cysteine on the mild steel surface followed a Langmuir isothermmodel with a standard free energy of adsorption (⊿G0ads) of -35.1 kJ·mol-1.  To clarify the type of interaction between mild steel surface and cysteine molecules with a molecular orbital approach, electronic properties, such as, the highest occupied molecular orbital (HOMO) energy, the lowest unoccupied molecular orbital (LUMO) energy, and the frontier molecular orbital coefficients have been calculated. Energy gaps for the interaction of mild steel surface and cysteine molecules (ELUMOFe-EHOMOCys and ELUMOCys-EHOMOFe) were used to determine whether cysteine molecules acted as electron donors or electron acceptors when they interacted with the mild steel surface. The local reactivity was evaluated through the condensed Fukui indices. Theoretical calculations were carried out using the density functional theory (DFT) at B3LYP level with the 6-311++G(d,p) basis set for all atoms by Gaussian 03W program.     

Electrochemical Behavior of Platinum-Modified Polyaniline Films in Sulfuric Acid Solutions of Carbon Monoxide

On the Pt–PAN–GC and PAN–Pt electrodes in H₂SO₄solutions that are first saturated with CO and then rid of it, during anodic scans of E _r, oxidation peaks are observed at 0.85–0.95 V, which disappear only after repeatedly cycling E _rin the interval 0.65 to 1.1 V. The effect is attributed to the capability of a PAN film to sorb considerable CO amounts. The sorption interaction is of a chemical nature. The electrooxidation of CO in the film is closely related to the PAN oxidation, which results in its destruction.     

氧化钌/活性炭超电容器复合电极的电化学行为

电化学超电容器作为一种新一代储能系统具有广泛的应用领域. 直流充放电、循环伏安以及交流阻抗等实验显示了本文制备的活性碳材料以及复合电极材料具有良好的电化学性能.活性碳材料的质量比容量为172 F•g－1,采用无定形RuO2与上述活性碳复合制成的新型电极材料具有359 F•g－1以上的比容量和良好的功率特性，并对上述材料的双电层电容和法拉第准电容等电化学特性进行了详细的讨论.     

Anodic Dissolution of Palladium in Sulfuric Acid: An Electrochemical Quartz Crystal Microbalance Study

Regularities of formation of a palladium oxide layer and its cathodic reduction in 0.5 M H₂SO₄ at 0.5–1.3 V (SHE) are studied by cyclic voltammetry, x-ray photoelectron spectroscopy, and electrochemical quartz crystal microbalance. A pure Pd plate and a 0.5-m-thick Pd coating on gold-sputtered quartz crystal is used for electrochemical and microgravimetric studies. It is shown that a Pd electrode dissolves electrochemically in 0.5 M H₂SO₄ when its potential is cycled between 0.5 and 1.3 V. In the case of 0.5-m-thick Pd coating on the gold substrate, the decrease in the electrode weight during one anodic–cathodic cycle is 1.0–1.5 g/cm². It is suggested that anodic process at 0.5–1.3 V (SHE) represents electrochemical oxidation of palladium, yielding a surface layer of poorly soluble Pd(OH)₂ and/or PdO phases, as expressed by the equation Pd + 2H₂O (Pd(OH)₂/PdO)_s + 2H⁺ + 2e. This surface layer, (Pd(OH)₂/PdO)_s, undergoes reduction during the cathodic process. About 5% of the total amount of ionized palladium dissolve in electrolyte.     

硫酸交联壳聚糖膜质子传导行为的研究

制备了硫酸交联壳聚糖膜, 通过研究其质子传导性能、力学性能、化学成分及结构变化, 分析了硫酸与壳聚糖分子间的交联方式, 并对质子传导机理进行了解析. 结果表明, 硫酸交联可显著改善壳聚糖膜的质子传导能力与力学性能, 这种改善作用在交联6 h后趋于稳定, 交联6 h后的壳聚糖湿膜在室温下时质子传导率为0.0472 S• cm^－1, 比未交联的壳聚糖膜提高5倍左右. 硫酸交联壳聚糖膜中的质子传导率与温度的关系符合Arrhenius定律, 质子传导激活能为18 kJ/mol, 其传导机制应属于Grotthus机制. 硫酸对提高壳聚糖膜的质子传导能力主要有两方面的作用: (1) H₂SO₄可使壳聚糖分子中NH₂质子化形成NH₃^＋. (2) 处于两个氨基之间的SO₄^2－在质子传递过程中起离子桥梁作用, 参与以水分子为载体的质子传导过程, 从而减小质子传导的阻力, 提高了质子传导率.     

Al/Pb-0.2%Ag阳极在氟离子和硫酸体系中的电化学行为

为了研究铝基铅银合金阳极在含氟离子和硫酸的体系中电化学行为,对含银0.2%的铝基铅银合金阳极(Al/Pb-0.2%Ag)分别在不同氟离子(F^-)和硫酸浓度下进行循环伏安测试和恒电流极化曲线进行了测试。 结果表明,F^-浓度升高时,对阳极表面单质铅氧化成二价铅以及二价铅氧化成四价铅有抑制作用,对四价铅还原为二价铅有抑制作用,但是对二价铅还原为单质铅有促进作用;此时析氧反应受阻,氧化成膜反应将被促进;硫酸浓度升高时,阳极上面铅的氧化和还原程度均先增大后减小;硫酸浓度为20 g/L、F^-浓度0.1 g/L时阳极的氧化成膜和析氧反应最为有利。     

Electrochemical Behavior of Diphenyl Disulfide and Thiophenol on Glassy Carbon and Gold Electrodes in Aprotic Media

The investigation of the electrochemical reduction processes of C₆H₅SSC₆H₅ and C₆H₅SH in CH₃CN using cyclic voltammetry indicates a different behavior on GC and Au electrodes. On GC surface adsorption phenomena are absent, the electrochemical reduction process is irreversible and diffusion controlled. For both the starting molecules the same species, C₆H₅S^?, is formed upon reduction. The E° values of the reduction processes were determined by convolution method and the standard free energy of the S? S bond of C₆H₅SSC₆H₅ estimated. On Au surface instead, a self‐assembled monolayer of C₆H₅SAu_ads originated after the S? S or S? H bond breaking can be observed by simply dipping the electrode in solution of C₆H₅SSC₆H₅ and C₆H₅SH, respectively. The properties of the SAM were investigated by electrochemical reduction of the adsorbed thiolates. On Au electrode the reduction processes involve C₆H₅SAu_ads and give rise to desorbed C₆H₅S^?. A neutral radical is obtained by electrochemical oxidation of thiolate anion. It reacts rapidly with the electrode surface to give the S‐Au bond again.     

IrO2基体上阳极电沉积MnO2的电化学行为

采用极化曲线和循环伏安等电化学方法, 对不同温度下IrO₂电极在MnSO₄镀液与硫酸溶液中的电化学行为进行对比研究, 并以镀液中极化曲线上不同电流密度值进行阳极电沉积, 测量镀速大小. 研究结果表明:IrO₂电极在镀液中同时发生阳极电沉积反应和析氧副反应, 阳极电沉积反应对析氧反应具有明显的抑制作用; MnO₂的阳极电沉积过程较复杂, 存在Mn³⁺中间产物, 既有Mn³⁺→Mn⁴⁺的电沉积过程, 也有Mn³⁺的水解及水解产物的脱附的过程, 水解反应的存在严重降低了MnO₂的阳极电沉积的电流效率; MnO₂的阳极电沉积存在一定的电位区间, 在此区间, 镀速存在最大值.     

Mg-Li电极在NaCl溶液中的电化学行为

应用熔炼法制备含Li量为8.5%和14%的两种Mg-Li合金,分别由电势线性扫描、计时电流、交流阻抗和失重法等检测Mg-Li电极在NaCl溶液中的电化学特性,SEM观察其放电表面形貌.结果表明:Mg-14Li电极比Mg-8.5Li电极有较负的开路电位、更大的放电电流和较高的放电效率,但附着电极表面的疏松产物易于脱落.Mg-8.5Li电极的放电效率高于Mg-14Li电极的放电效率.两种电极在低恒电位放电电流效率均高于较高恒电位的放电电流效率.     

Electrochemical Behavior of Electrodes Containing Single-Walled Nanotubes

The differential capacitance and voltammograms of electrodes that contain single-walled carbon nanotubes are measured in aqueous electrolytes. The discovered dependence of the capacitance on the measurement frequency is attributed to structural features of nanomaterials used. Electrochemical characteristics of nanotube electrodes are close to those of glassy carbon electrodes, with the difference that the discharge current in the former is substantially higher at cathodic potentials in the presence of N₂O. This effect is presumably caused by an autoelectron emission of electrons from nanotubes into electrolyte.     

Electrochemical Behavior of Mn5Si3 and Mn5Ge3 in Sulfuric Acid Solutions

Electrochemical behavior of Mn₅Si₃, Mn₅Ge₃, Mn, Si, and Ge in sulfuric acid solutions is studied by steady-state and cyclic voltammetry. The cathodic process on Mn₅Ge₃ is defined by the metallic component. During anodic polarization of Mn₅Si₃, manganese selectively dissolves out of the silicide lattice and silicon that remains on its surface oxidizes to SiO₂, with the Si anodic dissolution rate plummeting down (by 4 orders of magnitude as compared with Mn). The anodic dissolution of Mn₅Ge₃ leads to ionization of both Mn and Ge. The anodic hardness of Mn₅Ge₃ is lower than that of Mn₅Si₃.     

CoTiO3改性K2FeO4电极的电化学行为

CoTiO3改性K2FeO4电极的电化学行为;K2FeO4;CoTiO3;改性电极; 放电电位     

Electrochemical Behavior and Determination of Uric Acid at Single-Walled Carbon Nanotube Modified Gold Electrodes

The voltammetric behavior of uric acid was studied at a single-walled carbon nanotube (SWNT) modified gold electrode. Uric acid can effectively accumulate at this electrode and produce an anodic peak at about 0.45 V (vs. SCE) in pH 5.0 sodium acetate buffer solutions (HAc-NaAc). The experimental parameters, such as solution pH, accumulation time, and amount of SWNT, were optimized for determination. Under the optimum conditions, the anodic peak current is linear to the uric acid concentration over the range of 1.0×10⁻⁷ M to 2.5×10⁻⁵ M with a correlation coefficient of 0.998. The detection limit was 5.0×10⁻⁸ M for 60 s accumulation. The electrode could be easily regenerated and exhibited good stability. A 5.0×10⁻⁶ M uric acid solution was measured ten times using the same electrode, and the relative standard deviation of the peak current was 1.3%. This method was successfully applied to the determination of uric acid in human urine samples, and the recovery was 97–99%. The feasibility for simultaneous determination of xanthine, ascorbic acid and uric acid was discussed. These species did not interfere with each other in a certain concentration range. The influence of some surfactants on the anodic peak was also examined.     

A Study on the Electrochemical and Electrochemiluminescent Behavior of Homogentisic Acid at Carbon Electrodes

The electrochemical oxidation and electrochemiluminescent behavior of homogentisic acid (HGA) has been studied in aqueous solutions over a wide pH range by linear sweep voltammetry, cyclic voltammetry, chronocoulometry at a glassy carbon electrode, by controlled potential electrolysis at a large area spectroscopic graphite electrode, and by spectroelectrochemistry at an optically transparent drilled holes graphite (DHG) electrode in a thin‐layer cell. The studies reveal that the electrochemical oxidation of HGA at carbon electrodes is a reversible process involving two‐electron, two‐proton transfer. In addition to the electrochemical oxidation, the chemical oxidation of HGA by dissolved oxygen was investigated by spectroscopic method combined with voltammetry. It was revealed that HGA is fairly stable in strongly acidic media but readily oxidized by dissolved oxygen in alkaline media giving rise to 1,4‐benzoquinone‐2‐acetic acid, the same product as that of electrooxidation of HGA. This oxidation product is stable in acidic, neutral and weakly alkaline media, but can further degrade in strongly alkaline media yielding oxalate as the final product. The electrochemiluminescent mechanism of HGA in the presence of Ru(bpy)₃²⁺ at a glassy carbon electrode was also investigated in detail, based on which a sensitive ECL method for determination of HGA was developed, and the detection limit was 3.0×10^?8 mol L^?1.