扫描电化学微探针的发展及其在局部腐蚀研究中的应用

简要概述当前国内外具有空间分辨能力的扫描微探针技术及其在腐蚀研究中的应用,包括扫描微电极技术(SMET)、扫描电化学显微镜(SECM)、原子力显微镜(AFM)、扫描Kelvin探针技术(SKP)等,其中SMET、SECM、SKP及局部交流阻抗技术可直接测定腐蚀电极表面或界面电化学不均一性的分布图像,而原子力显微镜技术则是通过分子间作用力从纳米尺寸测量腐蚀过程表面形貌的变化.文中侧重介绍作者近年先后建立的具有微米空间分辨度的电化学微探针技术,并利用各种扫描探针技术研究金属/溶液界面电化学不均一性及其局部腐蚀过程.研究表明,空间分辨电化学方法的发展及应用,加深了人们对金属表面和金属/溶液界面电化学不均一性,特别是金属局部腐蚀发生、发展及过程机理的认识.     

椭圆偏振光谱技术的腐蚀研究应用

椭圆偏振光谱技术是一种高度灵敏、非破坏性的原位实时表征技术,可获取腐蚀过程“电极材料-介质”界面的动态变化信息,因此在腐蚀研究中得到了广泛应用. 本文结合解析椭圆偏振光谱数据所采用的光学模型的发展,介绍了近年来椭圆偏振光谱技术在腐蚀研究中的典型应用,并分析了该技术的发展趋势.     

Pd/Mm(富铈稀土)薄膜电极在KOH溶液中的电化学行为

利用磁控溅射法制备了Pd/Mm(Mischmetal)混合稀土薄膜,采用X射线衍射、AFM及循环伏安和交流阻抗谱等电化学测试技术研究了Pd/Mm稀土薄膜的晶体结构、表面形貌及其在KOH溶液中的电化学行为.结果表明,Pd/Mm薄膜表面的Pd层由纳米级的孤岛状颗粒构成,颗粒大小为100～200 nm.循环伏安法研究表明,氢的电化学氧化和还原均通过表面Pd金属层进行.Pd/Mm稀土薄膜电极的交流阻抗图由两个容抗弧组成,低频区的容抗弧对应氢在电极中的固态扩散过程,而高频段的容抗弧对应氢在电极表面的电化学还原过程,其中氢在薄膜电极内部的扩散是速率控制步骤.     

电活性分子L-B膜修饰CdSe薄膜电极的光电化学研究

用电活性分子——硬脂酸二茂铁酯L-B膜修饰了薄膜CdSe电极,在单色光650nm光照下用循环伏安法研究修饰的薄膜电极的光电化学性能。研究结果指出经多层L-B膜修饰后,薄膜CdSe电极的,I-V性能和光稳定性都有明显改善。用界面能级关系讨论了硬脂酸二茂铁酯L-B膜在光照的CdSe薄膜/Fe(CN)₆^4-溶液界面起传递电荷的中介作用,加速了界面的电荷转移。     

Na2CO3对TiO2纳米管电极表面光电化学水分解反应的催化作用研究

光生载流子在半导体/溶液界面处发生的表面复合过程,是制约半导体光电极体系光-电转化效率提高的关键因素之一.本文利用光电流测量和交流阻抗等技术,初步研究了Na2CO3对TiO2纳米管电极表面光电化学水分解反应的催化作用,并对"TiO2/溶液"界面处与阳极析氧有关的光生电荷传输过程及特点进行了探讨.结果表明,在0.5 mol.L-1NaClO4溶液中加入少量的Na2CO3(1mmol.L-1),能够显著促进光生空穴穿过TiO2/溶液界面向溶液中的传输,有效地抑制光生载流子的表面复合过程,从而相应地增大了外电路的光电流,并使TiO2光电极体系的光-电转化效率得到提高.     

原位衰减全反射表面增强红外光谱实验技术

介绍了原位研究电极,溶液界面反应的技术--衰减全反射表面增强红外光谱实验技术(ATR-SEIRAS)的产生背景和工作原理,重点描述了ATR-SEIRAS实验技术的关键:光谱电化学池的构造和薄膜电极的制备.与IRAS相比,ATR-SEIRAS技术可以更容易消除溶剂的背景吸收,获得较高的表面灵敏度,而且允许物质在电极表面自由扩散.与循环伏安相结合,利用ATR-SEIRAS技术可以实时监测电极,溶液界面问的反应.选择了利用ATR-SEIRAS实验技术原位研究功能表面的构造和性质、分子识别和反应中间体的形成等方面的应用实例,分析了ATR-SEIRAS实验技术的研究方向.     

染料敏化太阳电池中双层结构TiO2薄膜空间的电子分布与接触界面转移过程

采用电化学阻抗谱(EIS)研究了双层结构TiO2薄膜的电子积累和与电解液接触界面的电子转移过程. 通过制备纳米颗粒单层和纳米颗粒/亚微米颗粒双层2种不同微结构的TiO2薄膜电极, 对其电容分布、 局域态密度、 薄膜内部电子传输和固/液界面电子转移过程进行了研究. 分析了纳米颗粒/亚微米颗粒双层结构电极对染料敏化太阳电池(DSC)性能的影响. 结果表明, 一定数量的电子会积累在亚微米颗粒层中引起薄膜电极化学电容的增加. 在纳米颗粒层上端覆盖亚微米颗粒后降低了界面复合电阻, 但对薄膜电极的传输性能影响较小. 因此在筛选和制备DSC散射层材料时除应具有良好的光散射性能外, 还应考虑材料的化学电容和界面转移电阻等因素.     

交流示波极谱法中i_f-E曲线的研究——Ⅷ.“电极/溶液”界面动态双电层微分电容的快速测量

“电极/溶液”界面动态双电层微分电容是电极过程动力学中一个重要的物理量.但其测量方法.多数仍停留在对逐一测定的数据点进行作图分析上.本文以i(?)-E曲线上电流峰的理论公式为基础,提出了一个快速测量“电极/溶液”界面动态双电层微分电容的新方法.     

Au修饰薄膜CdSe电极的界面动力学行为的研究

研究了Au修饰的薄膜CdSe电极在多硫溶液中的瞬态光电流行为,测量了界面异相电荷转移,表面电荷复合及光腐蚀反应速度常数K_F,K_R及K_c。结合了光电子能谱(XPS)及扫描电镜(SEM)表面分析,对三种不同Au量修饰的薄膜CdSe电极进行界面动力学行为的分析。     

电化学还原预处理对BiVO_4薄膜电极光电化学氧化水性能的提高

在酸性水溶液中(pH=2.0),采用电化学还原(ER)方法对BiVO4薄膜电极进行预处理,并探讨了其对薄膜电极光电化学氧化水性能的影响.结果表明,这种预处理可显著提高电极的光电化学氧化水的性能,且具有良好的光电化学稳定性.利用扫描电子显微镜、X射线衍射、拉曼光谱、光电子能谱、紫外-可见漫反射光谱、荧光光谱、电化学阻抗谱及Mott-Schottky等方法对ER处理前后的电极进行了表征.结果表明,ER预处理使电极粗糙度增大,表面积增大约1.4倍;电极材料的晶型无明显变化,但V—O对称伸缩振动略有红移;表面Bi,V和O结合能变小,Bi3+部分被还原,Bi/V原子比增大;ER处理导致电极平带电位负移,光生载流子在薄膜电极/溶液界面转移速率加快,表面复合速率降低.这些变化和表面积增加是BiVO4电极光电化学性能提高的主要原因.     

椭圆偏振光谱方法对电化学的研究及应用

椭圆偏振光在固体表面入射和反射后,光学参量△,Ψ及其所表征的偏振状态,将因固体表面膜的厚度、性质不同而发生相应的变化．测定△,Ψ及其变化规律、可为固体材料、表面膜厚度、表面或界面上发生的有关物理或化学变化等直接或间接地提供信息,其灵敏度可反映表面膜层０．１～０．０１ｎｍ厚度的变化．因此,椭圆偏振光谱（下称椭圆法）在固体物理、表面化学、金属表面腐蚀、生物大分子表面等研究领域具有重要价值［１］．该法能检测的表面膜厚相当于电极上的单分子层的尺寸,特别适用于从分子水平上研究电化学体系,是最灵敏的光谱电化…     

Heterogeneous electrocatalysis: a core field of interfacial science

Heterogeneous electrocatalysis involves chemical reactions occurring in an electrochemical cell at the surface of an electrode, that is, at the electrochemical interface. The reaction rates are set by electrode surface structure, electrode potential, and can be adjusted by other variables specific to the field of electrochemistry. In contrast to reactions occurring at the solid/gas interface, electron transfer usually takes place at the electrochemical interface, which may lead to new product formation (in catalytic electrosynthesis), or allows one to harvest electrons in fuel cells. In the Opinion, papers describing catalytic materials used in a proton exchange membrane fuel cell are highlighted, and those related to recently developed research methodology of heterogeneous electrocatalysis receive a particular emphasis. Conclusions are made as to the future development of the field.     

Optical-facilitated single-entity electrochemistry

Single-entity electrochemistry focusing on the study of transient electrochemical process at the confined interface, has become a promising field that addresses questions from multi-disciplines such as cellular biology, material chemistry, organic chemistry, etc. It offers the fruitful information hidden in bulk electrochemical measurements. As the optical techniques improve in spatial and temporal resolution, the combination of electrochemistry with optical microspectroscopy provides more comprehensive information of single-entity electrochemistry. Herein, we review recent progress made in optical–electrochemical measurements covering three aspects from the precise localization and temperature measurements of single compartments, to the in-situ tracking of dynamic behaviors of single nanoparticles in electrochemical process, and to the monitoring confinement-controlled electrochemistry at the single molecule/ion level. The review demonstrates how these optical methods are innovatively integrated with single-entity sensing. It also reveals how these optical–electrochemical combinations push single-entity electrochemistry forward.     

Characterization of ultrafast processes at metal/solution interfaces: Towards femtoelectrochemistry

The essential part of electrochemistry is charge transfer. To understand this process in great detail, one needs to probe the relevant kinetics and dynamics on time scales spanning from femtoseconds to seconds or even longer. Although a conventional electrochemical detection scheme is sufficient for nanosecond or slower processes, it does not offer high enough time resolution for probing ultrafast processes, such as solvent reorganization, electron tunneling, and surface isomerization, that occur on faster, for example picosecond or femtosecond, timescales. These are indispensable parameters in the advanced charge transfer theories. In this review, some recent studies using ultrashort lasers to explore the ultrafast dynamics at the metal/solution interface are reviewed. The focus is on optical pump-probe and optical pump-push with electrochemical probe schemes. The connection of these studies with conventional electrochemistry and the limitations of these detection schemes are discussed.     

Electrochemical Surface Science This manuscript is based on the Bonhoeffer-Eucken-Scheibe lectures of the Deutsche Bunsengesellschaft, given by the author at Erlangen, Berlin, and Leipzig in 1999/2000

The last 30 years have seen remarkable changes in interfacial electrochemistry, particularly in the kind of questions that were addressed in electrochemical studies. Ever since classical surface science, traditionally performed under ultrahigh vacuum conditions, has succeeded in describing surfaces and surface reactions on a molecular level, electrochemists longed for a microscopic understanding of the solid/electrolyte interface and, at the same time, searched widely for new experimental ways to reach that goal. Herein, studies are described concerning the structure and the dynamics of bare and adsorbate-covered electrode surfaces and of metal deposition as a simple, yet important, electrochemical process. In all these cases, the scanning tunneling microscope plays a pivotal role emphasizing the surface-science approach to the problems.     

椭圆法用于阳极溶出伏安法测定铜的研究

用新物理量Ｖｏｐ的椭圆法定性地分析电化学体系已十分有效。鉴于椭圆法能灵敏检测电极表面０．１ｎｍ厚度物质的优点，如能用于定量电化学分析，可能提高现有电化学分析方法的检测限１个数量级以上。本文研究是否可能以及如何实际应用椭圆法于电化学定量分析。结果表明此法简单，并有满意的灵敏度。     

单体动态电化学

由于个体的差异性和异质性作用,整体平均测量掩盖了个体的本征性质和电化学性能之间的关联.单体碰撞电化学作为一种强大而方便的电化学方法,已被用于研究超微电极上自由扩散的单个个体随机碰撞过程中的电化学行为.然而,个体的动态行为与其电化学反应过程息息相关.因此,对于单体动态电化学行为的研究可实时获取单体在电极界面上的动态电化学...     

Optical and Electrochemical Combination Sensor with Poly‐Aniline Film Modified Gold Surface and Its Application for Dissolved Oxygen Detection

Poly‐aniline (PAn) film can be oxidized by contacting oxygen in an electron‐transfer reaction and its redox state, for instance the open circuit potential and the dielectric constant, is quantitatively related to oxygen concentration. This feature may contribute to an improved application of dissolved oxygen (DO) detection with the combined optical and electrochemical sensor. In this paper, PAn is used as a sensing surface to detect DO by the combination sensor composed of electrochemistry and total internal reflection imaging ellipsometry (EC‐TIRIE). Results demonstrate that both optical and electrical signals show a logarithmic correlation with DO concentration (0–20 ppm). Compared with the results obtained only with the gold surface, both the optical and electrical signals of the EC‐TIRIE sensor for DO detection are amplified with the PAn modified gold surface.     

Coordination‐Based Molecular Assemblies of Oligofurans and Oligothiophenes

Molecular assemblies (MAs) of oligofurans and oligothiophenes were formed from solutions on various substrates. These films were obtained by alternating deposition of organic chromophores (oligofurans or oligothiophenes) and a palladium salt. These coordination‐based MAs were characterized by UV/Vis spectroscopy, spectroscopic ellipsometry, atomic force microscopy (AFM), X‐ray reflectivity (XRR), X‐ray photoelectron spectroscopy (XPS), and electrochemistry. The MAs exhibit similar electrochemical behavior and their growth and structure are apparently not affected when different organic template layers are used. The density of the MAs is a function of the structure of the molecular component. The oligothiophene density is approximately 50 % higher than that observed for the oligofuran‐based assemblies. The optical and electrochemical properties of the MAs scale linearly with their thickness. The UV/Vis data indicate that upon increasing the film thickness, there is no significant conjugation between the metal‐separated organic chromophores. DFT calculations confirmed that the HOMO–LUMO gap of the surface‐bound oligofuran and oligothiophene metal oligomers do not change significantly upon increasing their chain length. However, electrochemical measurements indicate that the susceptibility of the MAs towards oxidation is dependent on the number of chromophore units.