磁场作用下铁电极的不均匀阳极溶解

采用电化学方法以及扫描电镜形貌观察研究了磁场对铁在硫酸溶液中的阳极溶解的影响 .恒电位极化测试结果表明 ,随外加阳极电位的增加 ,磁场的存在将加速阳极溶解 ,使振荡态或钝态变为活性溶解态 ,维持钝态 .于特定电位下与重力方向平行的电极表面两侧将因局部溶解加速而出现凹陷 .由于电极周边浓度梯度场的特殊性以及磁场的作用方向导致了铁的不均匀阳极溶解     

Fe-Cr-Ni合金碱性SCC的电化学预测方法

应用动电位扫描研究了Fe_Cr_Ni合金 (80 0M)C形环在含硫代硫酸钠杂质的热浓碱溶液中的应力腐蚀破裂 (SCC)行为 .测量了 80 0M合金试片与C形环试样恒电位极化时的稳态溶解电流ist,据此绘制了简化模拟“稳态”恒电位极化曲线 ,并将该极化曲线的ist与低电位下的稳态钝化电流ip之比 (RPD=ist/ip)定义为极化溶解敏感指数 .发现 80 0M合金C形环发生碱性SCC的电位区 (E =- 30～ 4 0mV)处于慢扫阳极极化曲线的钝化区 ,并对应于快扫极化曲线的钝化_过钝化溶解转变区 ;在该敏感电位区 ,试片与C环形试样的ist位于简化的模拟稳态恒电位极化曲线的过钝化区 ,试片与C形环试样两者的极化溶解敏感指数值很接近 (分别为 2 .5 5～ 7.0 3和 2 .5 2～ 6 .0 0 ) .综合稳态溶解电流密度 ,极化溶解敏感指数等有关信息 ,提出了一种碱性SCC的电化学预测方法     

镍铂修饰n型硅电极光电解析氧

本文以n/n^+-Si半导体为基底, 通过碱溶液刻蚀处理和Ni/Pt双层金属膜表面修饰后作为光阳极, 用于1.0mol·dm^-^3KOH溶液中光助电解水析氧。在恒电势1.0V(相对HgO/Hg电极)和90mW·cm^-^2光照射下, 最佳电极的析氧电流达到65.2mA·cm^-^2, 稳定性实验表明, 连续光照不超过200小时, 光电极具有良好的抗腐蚀性。对电极表面进行了X-光电子能谱(ESCA)分析。     

金属修饰半导体硅组成光电化学电池的研究

本文以n/n^+-Si和p/n^+-Si为基底, 通过铂、镍等金属膜表面修饰后组成光电化学电池, 探讨了金属/n-Si间的Schottky势垒对电池开路光电压的影响。研究了铂膜修饰电极的光电化学性能。用p/n^+-Si电极, 在65mW·cm^-^2的光照射下, 最佳电池的输出参数是: 开路光电压0.530V, 短路光电流47.6mA·cm^-^2, 填充因子0.35, 光电转换效率13.6%, 连续照光75小时, 电池性能基本稳定。     

金属鈍化理論的进展

一、前言在空气中或水溶液中绝大多数金属就其热力学性质而言本来是不稳定的,能自发地氧化为氧化物或其他盐类。若是向水溶液中加入氧化剂(HNO_3,H_2O_2,Fe~( )等)或是将金属作为阳极而加以极化,则金属的氧化过程将更迅速地进行。本来可以设想,若是我们不断增大氧化剂浓度或是增大极化电位、极化电流,那末金属的氧化速度也会相应地不断加大。然而,这种推想只在一定限度内是正确的,若超过了某一限度就会观察到正好相反的结果。例如,若是氧化剂浓度增高到某一临界值以上,则金属的溶解速度不是增大而是剧烈的减小了。若是使极化电位超过某一临界值,则金属的溶解电流也会大大降低。在恒电流极化时,若是极化电流密度超过某一临界值,则金属的电位会大     

硅在HF溶液中阳极溶解的研究

Uhlir及Turner早在50年代就已发现^[1,2],硅在HF溶液中阳极极化时,阳极电流大于某一特定值硅表面会发生电抛光反应,而低于这个值硅表面则会形成一层不同颜色的多孔硅层.1990年Canham发现多孔硅层在室温下有光致发光现象^[3],受到科学界的高度重视,在世界范围内掀起了研究多孔硅的热潮^[4].众多的研究表明,多孔硅的发光性能与其微孔的多少、大小和分布密切相关.但多孔硅要发展成为可实用的光电子材料,首先必须制备出微孔分布均匀,孔径及孔深可控的多孔硅材料.这就有必要弄清多孔硅的形成机理^[5],了解硅在HF溶液中的溶解过程及机理.为此,本文对不同掺杂浓度不同导电类型的(111)晶面单晶硅在HF溶液中的电流-电压(I-V)、电容-电压(C-V)特性进行了研究,并对这些特性进行了分析.     

酸性AlCl3-BMIC离子液体中的铝阳极溶解

采用线性扫描伏安法研究了Lewis 酸性AlCl₃-BMIC (BMIC: 1-butyl-3-methylimidazolium chloride)离子液体中铝电极的溶解. 铝电极在阳极极化时出现了钝化现象, 钝化是由于在铝电极表面形成了固体AlCl₃钝化膜造成的. 铝的电化学溶解过程可以依次分为三个区: 电化学控制区、过渡区和钝化区. 在电化学控制区, 铝的电化学溶解速率随着电位的正移而逐渐增加; 在过渡区, 由于电极表面AlCl₄^-和Al₂Cl₇^-浓度发生改变而析出固体AlCl₃使得铝电化学溶解速率随着电位的正移而逐渐减小; 当钝化膜形成之后, 铝的电化学溶解速率不再随着电位的正移而发生改变, 铝溶解进入钝化区. 增加搅拌、升高温度、降低离子液体AlCl₃摩尔分数都可以增加铝溶解阳极极限电流密度.     

铅锡合金在硫酸溶液中生长阳极Pb(Ⅱ)氧化物膜的机理

用交流阻抗、开路电位衰退及线性电位扫描等方法在0.9V(vs.Hg/Hg₂SO₄)和4.5mol/LH₂SO₄溶液中,研究了铅及Pb-Sn合金电极上所生长的阳极氧化物膜.实验结果表明,阳极膜由溶解-沉淀机理控制生长,膜中微粒间为液膜,借助液膜作为离子通道可使膜中微粒发生阳极反应,锡有利于膜中PbO微粒表层阳极氧化为PbO^1+x(0相似文献   

覆铜板在NaCl溶液中的腐蚀电化学行为

应用线性极化、循环伏安(CV)及电化学阻抗谱(EIS)等电化学方法对覆铜板(CCL)和纯铜的腐蚀电化学行为进行了研究和比较. 结果表明, 覆铜板的耐蚀性弱于纯铜, 其阳极溶解过程与纯铜有所不同; 在较低电位下, CCL 以铜的氯化络合物的形式溶解, CuCl-2的扩散为该过程的控制步骤; 随着电位的升高, 腐蚀产物CuCl在电极表面形成疏松多孔的膜, Cl-在膜中的传输成为溶解过程的控制步骤. 电极表面CuCl 膜的消长过程是产生感抗弧的主要原因.     

锌电极在氢氧化钾溶液中阳极惰化时的表面相变的研究

本文试图进一步从动力学方面证明恒电位下的锌电极在KOH溶液中阳极惰化时,阳极溶解电流随时间而缓慢下降是由于“表面相变”所引起。用恒电位法测取了锌电极在不同浓度的KOH溶液中电流对时间的曲线。实验结果与推导的动力学方程式相符,表明在恒电位惰化条件下,锌电极表面上最初形成的[Zn(OH)_2]_(ad)在OH~-参预下徐缓地转变为较不易溶的[ZnO]_(ad),因而导致阳极溶解电流的下降。这一表面相变过程可表示如下:     

系列二羰基化合物的HeI紫外光电子能谱(UPS)及量子化学研究

报道了醌及苯并酸酐等系列二羰基化合物的气相HeI紫外光电子能谱。对各体系利用Gaussian94程序RHF/3-21G进行了构型优化,对得到的优势构型采用STO-6G基组进行了轨道计算。并结合计算结果对各分子体系的UPS谱进行了分析指认。计算结果分析显示:标题化合物的第一个电离峰均是由苯环部分的共轭π键电子电离及羰基的孤对电子电离引起的,且化合物的IP~1值随羰基在HOMO轨道中权重的增大而增大。各化合物的第二、三谱带都与羰基不同类型的孤对电子峰相关联。说明羰基为此类化合物的特征基团。且分子的对称性越高,羰基的孤对电子峰n^-和n^+的平均值越大,分裂值也越大。     

Effect of anodic potential on process of formation of polyporphyrin film in solutions of tetrakis(p-aminophenyl)porphin in dichloromethane

The electrode impedance spectroscopy technique was used to study the process of formation of a conducting polyporphyrin film on a Pt electrode from a 10^?3 M solution of tetrakis(p-aminophenyl)porphin in dichloromethane. An equivalent circuit is suggested for simulation of interface impedance in a wide range of working electrode potentials. It is shown that regions with a different mechanism of film formation are observed at an increase in potential from 0.0 to +1.0 V. The kinetics of film formation are studied at the potentials of +0.40, +0.60, and +0.80 V. It is found that good agreement is observed between the model and experimental data when the growing film is simulated using a Warburg element with a finite diffusion length. Conductivity and the diffusion coefficient of charge carriers in it are estimated on the basis of the suggested model for a film obtained at the potential of +0.40 V. It is shown that conductivity of a polyporphyrin film grows by more than an order of magnitude at an increase in deposition potential from +0.40 to +0.80 V.     

Electro-oxidation of formic acid catalyzed by FePt nanoparticles

The electrocatalytic oxidation of formic acid at a gold electrode functionalized with FePt nanoparticles was studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in a mixed solution of 0.1 M HCOOH and 0.1 M HClO4. The FePt bimetallic nanoparticles, with a mean diameter of 3 nm, were prepared by a chemical reduction method. The Au/FePt nanostructured electrode was prepared firstly by the deposition of FePt nanoparticles onto a clean Au electrode surface, followed by ultraviolet ozone treatment to remove the organic coating. In CV measurements, two well-defined anodic peaks were observed at +0.20 and +0.51 V (vs. a Ag/AgCl quasi-reference). The anodic peak at +0.20 V was attributed to the oxidation of HCOOH to CO2 on surface unblocked by CO, whereas the peak at +0.51 V was ascribed to the oxidation of surface-adsorbed CO (an intermediate product of HCOOH oxidation) and further oxidation of bulk HCOOH. From the onset potential and current density of the electro-oxidation of HCOOH, FePt nanoparticles exhibit excellent electrocatalytic activities as compared to Pt and other metal alloys. EIS measurements were carried out to further examine the reaction kinetics involved in the HCOOH electro-oxidation. The EIS responses were found to be strongly dependent on electrode potentials. At potentials more positive than -0.25 V (vs. Ag/AgCl), pseudo-inductive behavior was typically observed. At potentials between +0.3 and +0.5 V, the impedance response was found to reverse from the first quadrant to the second quadrant; such negative Faradaic impedance was indicative of the presence of an inductive component due to the oxidation of surface-adsorbed CO. The impedance responses returned to normal behavior at more positive potentials (+0.6 to +0.9 V). The mechanistic variation was attributed to the formation of different intermediates (CO or oxygen containing species) on the electrode surface in different potential regions. Two equivalent circuits were proposed to model these impedance behaviors.     

Potential‐Controlled Chromatography of Short‐Chain Carboxylic Acids

A chromatographic column was constructed which could be operated with an electrically conductive stationary phase of graphite particles. This column allowed chromatographic experiments at variable electric potentials of the column material. The chromatographic behavior of selected carboxylic acids was significantly influenced at positive column potentials. An equimolar mixture of three different carboxylic acids were separated at a potential of +600 mV (versus. Ag/AgCl). Surprisingly, the stereoisomers maleic and fumaric acid, which are identical in molecular mass and charge, could also be separated. Further improvements to the chromatographic performance were achieved by applying potential drops and linear potential gradients.     

New ab initio coupled potential energy surfaces for the Br(2P(3∕2), 2P(1∕2)) + H2 reaction

The three lowest (1A('), 2A('), and 1A(')) adiabatic potential energy surfaces (PESs) for the Br((2)P) + H(2) reactive system have been computed based on the multi-reference configuration interaction (MRCI) method including the Davidson's correction with a large basis set. These three adiabatic PESs have been transformed to a diabatic representation, leading to four coupling potentials. In addition, the spin-orbit matrix elements were also obtained using the Breit-Pauli Hamiltonian and the unperturbed MRCI wavefunctions in the Br + H(2) channel and the transition state region. Consequently, six coupling potentials were obtained and their characteristics were extensively discussed. Nonadiabatic quantum dynamics calculations for this system have been realized with these realistic diabatic potentials instead of previous semi-empirical diabatic potentials. Based on two-state model nonadiabatic calculations for the Br((2)P(3∕2), (2)P(1∕2)) + H(2) reaction, the Br((2)P(1∕2)) + H(2) reaction was found to show less reactivity than the Br((2)P(3∕2)) + H(2) reaction at collision energies beyond the threshold of the Br((2)P(3∕2)) + H(2) reaction. Our results are consistent with the previous studies on the XH(2) (X = F, Cl) system, which indicate that the adiabatically forbidden channel is dominant at low energies in the open-shell halogen atom plus H(2) reactions.     

Ruthenium/rhodium modified gold electrodes for the amperometric detection of hydrogen peroxide at low potentials

Electrodes of ruthenium/rhodium deposited as thin layers on gold foils were investigated. Ruthenium layers were radio frequency (r.f.) magnetron sputtered and the rhodium layers were made by vacuum evaporation. Hydrogen peroxide could be detected using the cathodic reduction at potentials lower than +170 mV or the anodic oxidation at higher potentials. Under flow injection conditions, H(2)O(2) was detected between 1 and 1000 micro M at a potential of -100 mV and between 2 and 500 micro M at a potential of +250 mV vs. Ag/AgCl/0.4 M KCl. The electrodes also showed high operational stability and selectivity against many electroactive substances. The selectivity against dissolved oxygen was investigated.     

离子液体中铜纳米粒子膜的电沉积制备及表面增强拉曼光谱

采用恒电位方法研究了室温离子液体1-丁基-3-甲基咪唑氟硼酸盐([BMIM]BF₄)中氧化铟锡(ITO)电极表面Cu的沉积过程. 结果表明, Cu²⁺在ITO表面经中间产物Cu⁺还原为Cu. 采用XRD和SEM对不同电位下沉积层的组成和结构进行了考察. 结果表明, 表面组成和结构与沉积电位有关. 在较正电位下沉积所得为Cu/Cu₂O的混合纳米粒子; 在较负电位下为Cu纳米粒子. 随着沉积电位逐渐变负, 其形貌经历了花状、 棒状向球形纳米粒子转变的过程, 且所得沉积膜逐渐变得致密, 其中Cu纳米粒子膜表现出较强的表面增强拉曼散射(SERS)活性, 并且SERS信号均一.     

Electrochemical behavior of 5-substituted 2-alkylidene-4-oxothiazolidine derivatives studied by cyclic voltammetry

This study demonstrates the electrochemical activity of selected 2-alkylidene-4-oxothiazolidine compounds containing different substituents at the C5-position on the Pt-electrode in 0.1 M TBAHFP + MeCN in the potential range from −2 V to 2 V. The mechanism of electrode processes is discussed. It is shown that a chemical step is involved in irreversible electrochemical processes. The effect of the substituent at the C5-position on reduction and oxidation potentials is also noted. The regions of a linear dependence of the current peak on the concentration of the compounds examined are determined. The text was submitted by the authors in English.