大气中无机盐粒水解过程中的微液滴现象

采用改变相对湿度, 无机盐/金属组合, 测定微液滴体系的pH值和电位分布等方法研究了微液滴形成和生长的特征. 结果表明, 微液滴的形成与大气腐蚀密切相关. 微液滴只在特定的盐粒/金属体系中出现, 微液滴区域具有较高的pH值和较高的电位分布. 此外, 微液滴形成和生长需要两个前提条件：第一, 环境相对湿度应高于盐粒水解液滴液面的饱和蒸汽压；第二, 在水解液滴下的金属能被液滴腐蚀.     

非平衡渗入条件下的电化学渗氢模型

提出非平衡渗入条件下的电化学渗氢数学模型,导出相应的渗氢电流暂态关系式。指出由稳态渗氢电流与试样厚度的关系可得表面渗入过程的动力学参数。讨论了阴极极化条件对氢扩散系数观测值的影响。     

溶液性质对微液滴现象的影响

考察了金属表面液滴性质对微液滴形成的影响并探讨了微液滴的来源. 不同pH值液滴附近微液滴形成特征表明, 高电位阴极区氧还原反应是微液滴形成的原因之一. 此外, 研究结果表明, 微液滴是由主液滴挥发的水蒸气经过气相“迁移”至主液滴附近金属表面上重新吸附凝聚形成的.     

ESEM observation of the process of hydrogen generation around the micro-droplets forming on AZ91 magnesium alloy

The process of hydrogen generation around micro-droplets on as-cast AZ91 magnesium alloy in an atmosphere of water vapor was in situ observed using an environmental scanning electron microscope (ESEM). The procedure for hydrogen generation was described. It indicated that the cathodic or anodic location gradually changed with the generation of hydrogen bubbles and the formation of corrosion products.     

Electroreduction of molecular oxygen on carbon electrode modified by dispersed silver

Silver particles are formed by electrochemical deposition on the carbon electrode surface. It is found that the deposition process occurs according to the progressive nucleation mechanism, which results in formation of silver particles with the size of 95 to 190 nm as dependent on the electrodeposition time. The values of silver particle size and support surface coverage by metal obtained on the basis of microphotographs indicate that cathodic polarization in the presence of dissolved oxygen results in particle size redistribution due to the reaction of silver particle dissolution with further deposition simultaneously with oxygen electroreduction. The reaction of molecular oxygen electroreduction on a carbon electrode with deposited dispersed silver occurs via a mixed two- and four-electron mechanism. The observed limiting reaction current is of diffusion nature.     

Activation,microstructure, and polarization of solid oxide fuel cell cathodes

Activation effect can be defined as the enhancement of the electrochemical performance or activity of the solid oxide fuel cell cathodes such as Sr-doped LaMnO₃ (LSM) with the polarization/current passage treatment under fuel cell operation conditions. In this paper, the activation effect of the cathodic polarization/current passage on the O₂ reduction reaction of the LSM-based cathodes is reviewed. In addition to the activation effect, cathodic polarization/current passage also has a significant effect on the microstructure of the LSM electrodes and the morphology between the LSM electrode and Y₂O₃-ZrO₂ electrolyte interface. A mechanism involving the incorporation of SrO species into the LSM lattice and the formation of oxygen vacancies is proposed for the activation effect of the polarization.     

Indole‐3‐acetic acid and N‐acetyltryptophan corrosion inhibition effects on mild steel in 1 M hydrochloric acid solution

Corrosion inhibition of indole‐3‐acetic acid and N‐acetyl tryptophan on carbon steel was investigated using polarization and electrochemical impedance spectroscopy (EIS). Polarization results revealed that corrosion inhibitors could reduce the rate of cathodic and anodic reactions on metal surface. EIS analysis showed inhibition efficiency of indoles increases by increasing the inhibitor concentration. The maximum inhibition efficiency was 97% and 80% in solutions containing 10 mM indole‐3‐acetic acid and 10 mM N‐acetyl tryptophan, respectively. The adsorption of inhibitors was found to follow Langmuir isotherm. Adsorption and film formation of inhibitors on the metal substrate were confirmed by calculating thermodynamic adsorption parameter (ΔG⁰_ads) and characterization of exposed metals' surface through contact angle measurements. Copyright © 2014 John Wiley & Sons, Ltd.     

锈层下碳钢的腐蚀电化学行为特征

采用极化曲线、线性极化电阻(LPR)和电化学阻抗(EIS)研究了海水中带锈碳钢的电化学行为,结果发现:长期浸泡的内锈层对电极过程有较大影响;短期浸泡,LPR和EIS测定的极化电阻(Rp)逐渐增大;而长期浸泡,Rp却逐渐减小;随着浸泡时间的延长,Rp出现了先增大后减小的变化趋势.将锈层逐层剥离后研究了碳钢的电化学行为,并结合傅里叶变换红外(FTIR)光谱和横截面结构分析表明,这主要是因为长期浸泡后,内锈层中出现了具有较高电化学活性的β-FeOOH,并且其含量随着浸泡时间的延长而逐渐增加.当进行电化学测试时,在对体系进行一定程度极化的过程中,β-FeOOH参与了阴极还原反应,使电极过程不再是简单的阳极金属溶解和阴极氧还原,加快了阴极反应速度,从而导致Rp逐渐减小.     

Oxygen reduction reaction on polycrystalline gold. Pathways of hydrogen peroxide transformation in the acidic medium

The mechanism of oxygen electroreduction on polycrystalline gold is studied in the acidic medium. Hydrogen peroxide is the main reaction product. However, two potential regions can be singled out in which the oxygen electroreduction reaction proceeds by different pathways. The first region is the potential interval close to the steady-state potential. Here, the oxygen electroreduction virtually completely produces peroxide. The second interval is the potential range of considerable cathodic polarization values. In this case, peroxide can be reduced to water. The low energy of hydrogen peroxide adsorption on gold determines the considerable overpotential of peroxide reduction. It is shown that on the gold electrode surface, the catalytic decomposition of peroxide occurs. The use of the method of electrochemical impedance spectroscopy allows the peculiarities of the oxygen reaction associated with hydrogen peroxide transformations to be revealed. In the acidic medium, the reactions of consecutive reduction of oxygen through the intermediate formation of hydrogen peroxide and the catalytic decomposition of the intermediate product are shown to proceed simultaneously. The ratio of rate constants of electrochemical stages depends on the potential. The chemical decomposition is observed both near the steady-state potential and in the cathodic region where considerable electrochemical reduction of peroxide occurs.     

Kinetics of Cathodic Reduction of Hypophosphite Anions in Aqueous Solutions

The kinetics of the cathodic reduction of hypophosphite anions in aqueous solutions is studied as a function of the electrode nature, the sodium hypophosphite concentration, and the solution pH. It is shown that the product of the reduction of hypophosphite anions is phosphorus. A scheme is proposed for the reduction process, according to which the phosphorus formation can proceed via two parallel routes—electrochemical and chemical—whose realization depends on the nature of the metal catalyst.     

酸性化学镀镍磷合金的动力学机理

通过极化曲线研究了3种不同溶液（阴极液、阳极液和完整镀液）的电化学行为,测定了主盐、还原剂浓度以及镀液pH和体系温度对化学镀镍沉积速率的影响. 与直接在镁合金上化学镀镍并使用重量分析法得到的沉积速率相比较发现,完整镀液体系的极化曲线才能真实地反映化学镀镍的沉积过程,其过程不能简单视为由彼此完全独立毫无关联的阴阳极半反应构成. 根据Butler-Volmer公式,本化学镀液体系的化学镀镍过程属混合控制,其表观反应活化能为42.89 kJ·mol^-1.     

硫酸亚铁对化学沉积钴-铁-磷合金中的影响(英文)

在以次亚磷酸钠为还原剂、硼酸为缓冲剂和柠檬酸钠为络合剂的碱性介质中,化学沉积钴 铁 磷合金和钴 磷合金.研究了沉积工艺,如pH值和主盐CoSO4/FeSO4的摩尔比对沉积速率的影响.发现镀液中的硫酸亚铁对钴 铁 磷合金沉积有阻碍作用,以致其沉积速率比钴 磷的低.电化学极化实验表明,硫酸亚铁既影响阳极过程又影响阴极过程,它降低了两者的极化电流和极化电势.电化学实验结果与沉积速度测量结果基本相符.     

Surface chemistry study of RuO2/IrO2/TiO2 mixed-oxide electrodes

DSA metal oxide electrodes such as the RuO(2)/IrO(2)/TiO(2) mixed system are widely studied for their excellent electrocatalytic activity. In order to understand their catalytic properties, the comprehension of the surface chemistry involved during electrochemical treatments is crucial. With this aim, RuO(2)/IrO(2)/TiO(2) mixed-oxide electrodes having various noble metal contents were studied by means of secondary ion mass spectrometry (SIMS). In particular, cathodic and anodic polarization and O(2) evolution reactions were carried out to test the electrode behaviour and SIMS analyses were performed after all these treatments. In this way, surface changes induced by electrochemical treatments and depending on electrode composition were widely investigated by SIMS, revealing, for example, the presence of hydration or preferential dissolution phenomena induced by electrochemical processing.     

Surface chemistry of RuO(2)/IrO(2)/TiO(2) mixed-oxide electrodes: secondary ion mass spectrometric study of the changes induced by electrochemical treatment

The IrO(2)/RuO(2)/TiO(2) ternary system is well known for its electrocatalytic activity towards oxygen- and chlorine-evolution reactions. Electrochemical processing induces noticeable chemical and morphological modifications on these electrodes, depending on the noble metal oxide content. In this work, cathodic/anodic polarization and the oxygen-evolution reaction were studied in order to evaluate the electrocatalytic activity at various noble metal oxide percentages. The best performing electrode (30 mol% noble metal oxides) was analyzed before and after electrochemical tests by means of secondary ion mass spectrometry (SIMS) in order to determine the chemical composition modification which occurred on the surface and in deeper regions of the mixed-oxide film.     

Copper in Acid Chloride Solutions: Electrochemical Behavior by Quartz Microgravimetry and Voltammetry

The cathodic deposition of copper on a gold electrode and its subsequent anodic dissolution in an acid chloride solution, where two successive stages of a one-electron transfer are distinguishable because of the stability of chloride complexes of Cu(I), is studied by voltammetry and quartz microgravimetry. The formation of a film of an intermediate compound of Cu(I) during the deposition and dissolution of copper is revealed experimentally. Techniques for identifying the intermediate solid species are suggested. During a cathodic polarization, a film of intermediate compound CuCl forms at a reduced concentration of chloride ions in the Cu(II)/Cu(I) process, while during the anodic dissolution of the copper deposit formed during the cathodic polarization the intermediates appear in the Cu(0)/Cu(I) process, the concentration of chloride ions notwithstanding. The change in the electrochemical behavior of the system caused by a decrease in the concentration of chloride ions is explained.     

N-乙烯基咪唑鎓盐聚合物的合成、表征及其电化学性能

以N-乙烯基咪唑、溴丁烷、丙烯酸乙酯为原料,合成了聚溴化N-乙烯基-N’-丁基咪唑以及溴化N-乙烯基-N’-丁基咪唑丽烯酸乙酯共聚物,通过红外、核磁、元素分析对其结构进行了表征．采用阴极极化曲线测试了其电化学性能,结果表明两者对铜离子阴极还原产生了极大的极化作用．     

The electrochemical properties of Ni<Subscript>3</Subscript>C carbide

The electrochemical properties of Ni₃C was studied. In acidic sulfate solutions, the carbide is characterized by high overpotential of its oxidation as compared with nickel. In the case of carbide oxidation, the anodic reaction orders with respect to anions are low, indicating a weak dependence of the rate of the anodic process on the solution composition. Significant differences in the kinetics of the anodic processes indicate different mechanisms of the oxidation of nickel and its carbide. The rate and kinetic parameters of the hydrogen evolution reaction are comparable on Ni and Ni₃C. In neutral and alkaline solutions, the metal and carbide samples were similar in their electrochemical characteristics. The anodically grown oxide film is thinner on nickel carbide than on nickel metal, and the oxide formed on the carbide is more readily reduced under cathodic polarization. This film is also more resistant to the pitting attack than the oxide film on nickel metal.     

Aqueous extract of <Emphasis Type="Italic">Argemone mexicana</Emphasis> roots for effective protection of mild steel in an HCl environment

The inhibition effect of aqueous Argemone mexicana root extract (AMRE) on mild steel corrosion in 1 M HCl has been studied by weight loss, Tafel polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy techniques. Results indicate that inhibition ability of AMRE increases with the increasing amount of the extract. A maximum corrosion inhibition of 94 % is acknowledged at the extract concentration of 400 mg L^?1. Polarization curves and impedance spectra reveal that both cathodic and anodic reactions are suppressed due to passive layer formation at the metal–acid interface. It is also confirmed by SEM micrographs and FTIR studies. Furthermore, the effects of acid concentration (1–5 M), immersion time (120 h) and temperature (30–60 °C) on inhibition potential of AMRE have been investigated by the weight loss method and electrochemical techniques. An adsorption mechanism is also proposed on the basis of weight loss results, which shows good agreement with the Langmuir isotherm.     

Electrochemical reactions at a copper electrode in copper-conducting solid electrolytes

Potentiostatic measurements are used to show that, depending on the overvoltage sign, either electrochemical deposition or dissolution of copper occurs at the Cu/Cu₄RbCl₃I₂ interface at overvoltages η > 8–10 mV. At η = 10–100 mV, the reaction rate is limited by the formation and expansion of dissolution centers at the copper surface during anodic polarization and crystallization centers, during cathodic polarization. At η > 120 mV, the reaction rate is limited by charge transfer; the exchange current density is 2.7 mA cm^?2 and the anodic transfer coefficient is ～0.45. Under anodic polarization, formation of electron holes in the electrolyte occurs in parallel with the copper anodic dissolution. Therefore, nonstoichiometry of the electrolyte emerges in the near-electrode layer and divalent copper accumulates there.