电催化界面和反应的电化学阻抗谱研究:经典永不褪色（英文）

本文章综述了电催化领域电化学阻抗谱(EIS)的相关研究.首先概述了从二十世纪初到现在这一专业领域的发展历史.然后介绍了电催化阻抗理论的几个里程碑.其中,着重介绍了目前分析电催化EIS数据的主流模型——Dolin-Ershler模型.之后,具体讨论了铂金单晶的双电层电容,特别是围绕这一基础课题的实验和理论上的挑战.我们质疑采用Dolin-Ershler模型获取稀溶液中双电层电容的合理性.因为在稀溶液中,双电层效应使得双电层电容具有频散特性,因而双电层电容的低频部分在分析过程中可能被遗失了.未来,我们期待看到新的实验去证明或反驳一个最近的理论预测,即铂电极在氧化物生成电位区域中具有非单调表面电荷关系和负双电层电容.     

钌镧氧化物涂层在NaCl 溶液中的电化学阻抗谱(EIS)研究

测量了钌镧氧化物涂层的电化学阻抗谱(EIS), 结合循环伏安(CV)及扫描电子显微镜形貌分析, 研究了钌镧氧化物涂层阳极在3.5% NaCl 溶液中电化学表面结构及电化学行为. 在非析氯反应区间, 该涂层EIS 数据的最佳拟合等效电路是R_s(R_ctQ_dl), 在析氯反应区间, 其等效电路为R_s(R_fQ_f)(R_ctWQ_dl). 高频段阻抗行为对应涂层的物理阻抗, 低频段对应涂层与溶液界面的电化学反应阻抗. 实验结果表明, 随着La 浓度增加, 氧化膜及双电层的伪电容增大, 且在La 含量30mol%时达到最大值, 与CV实验结果一致, 证明了加入La 能提高RuO₂涂层的电催化活性. 但在析氯反应区间, 涂层氧化膜的导电性在含La 大于30 mol%之后迅速下降, 在低频段产生Warburg 阻抗, 与其表面钝化和特性吸附现象有关,这是导致含La 70 mol%时电催化活性急剧下降的原因.     

粉末多孔镍电极电化学阻抗谱及其数学模型

镍电极反应动力学在大多情况下是受固态质子扩散过程控制的，以此为出发点建立了具有明确物理意义的镍电极电化学阻抗谱（EIS）的数学模型．并以该模型为基础，讨论了一些模型参数如双电层电容C（d1）、质子扩散系数D及活性物质位于半径γ0等的改变，电极的不同行电状态以及多孔镍电极中的传质过程对镍电极阻抗谱的影响．理论模型较好地解释了一些实验结果．     

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.     

双电层电容器电化学阻抗谱的实验研究

电化学阻抗谱(EIS)是一种很有用的研究电化学性能的技术. 理想的双电层电容器(EDLC)阻抗谱的尼奎斯特图由中高频的45°线和低频的与实轴垂直的直线组成, 可以用孔径分布-传输线模型来解释. 然而, 在研究工作中还发现, 在阻抗谱的高频区出现了半圆弧区域, 为此, 提出的等效模型认为半圆弧可以归因于活性材料之间的接触电阻和接触电容, 以及电极与集流体之间的接触电阻与接触电容. 还研究了充电过程、活性炭和电解液的电导率、导电添加剂和粘结剂的含量、隔膜、活性物质附载量和极片加压等因素对阻抗谱的影响. 其中, 充电截止电压、活性炭的电导率、导电添加剂的含量和极片加压对半圆弧部分影响较为显著.     

硫酸溶液中电化学改性石墨电极对Fe3+/Fe2+的电催化性能与准电容特性

通过循环伏安(CV)、恒电流充放电和电化学阻抗谱(EIS)等测试方法,研究了电化学改性石墨电极对硫酸溶液中Fe3+/Fe2+的电催化性能与准电容特性.结果表明:由于电化学改性石墨电极表面存在大量的含氧活性官能团,使其对Fe3+/Fe2+的氧化还原反应具有极高的电催化性能,并具有可逆反应过程特征.在含有0.5mo·lL-1Fe3++0.5mo·lL-1Fe2+的2.0mo·lL-1H2SO4溶液中,其表观面积比电容是不含铁离子硫酸溶液的1.808倍,达到2.157F·cm-2;同时,铁离子浓度的增大也能够进一步提高其电容量.Fe3+/Fe2+电对的加入增加了充放电时间,有效提高了电化学电容器(EC)的电容存储容量和高功率特性.电化学阻抗谱测试同样证实体系具有明显的电容特性.因此,可以利用电化学改性石墨电极表面的含氧活性官能团和溶液中Fe3+/Fe2+的氧化还原特性来共同储存和释放能量.     

双电层电容器电化学阻抗谱的实验研究(英文)

电化学阻抗谱(EIS)是一种很有用的研究电化学性能的技术.理想的双电层电容器(EDLC)阻抗谱的尼奎斯特图由中高频的45°线和低频的与实轴垂直的直线组成,可以用孔径分布-传输线模型来解释.然而,在研究工作中还发现,在阻抗谱的高频区出现了半圆弧区域,为此,提出的等效模型认为半圆弧可以归因于活性材料之间的接触电阻和接触电容,以及电极与集流体之间的接触电阻与接触电容.还研究了充电过程、活性炭和电解液的电导率、导电添加剂和粘结剂的含量、隔膜、活性物质附载量和极片加压等因素对阻抗谱的影响.其中,充电截止电压、活性炭的电导率、导电添加剂的含量和极片加压对半圆弧部分影响较为显著.     

尖晶石锂锰氧化物电极首次脱锂过程的EIS研究

研究了尖晶石锂锰氧化物电极首次脱锂过程中的电化学阻抗特征. 通过选取适当的等效电路拟合实验所得的电化学阻抗谱数据, 获得了首次脱锂过程中固体电解质相界面膜(SEI膜)的电阻、电容以及电荷传递电阻、双电层电容等随电极极化电位的变化规律.     

硫化物在铂电极上电氧化时空动力学的模型模拟和分析(英文)

根据铂电极上硫化物电催化氧化的反应机理,本文提取动力学模型并利用数值模拟研究了N型负微分阻抗(N-NDR)振荡区域的电极表面时空反应动力学.在均相体系模拟中观察到电流简单振荡和复杂振荡,其来源于双电层电势自催化与传质限制和毒化物种吸附负反馈的相互耦合.为了更接近于真实体系,在模型中考虑了平行和垂直于电极表面两个方向的传质过程.模拟结果发现了与实验现象具有相同演化行为的复杂斑图,如行波和闪烁波;同时在传质耦合体系模拟中观察到双电层电势双臂螺旋波.本研究工作促进对电化学体系时空斑图的理解和预测.     

固液界面双电层的理论计算模拟

固液界面双电层在电化学中处于核心地位. 如何发展一个理论方法,在该方法的框架下计算双电层的平衡性质和动力学性质一直以来都是理论研究的难点和热点. 本文总结了最近十几年第一性原理计算方法在计算双电层平衡性质和电催化反应的进展,如热力学方法、反应中心模型以及双参考方法. 并进一步详细地阐述了基于周期性均匀介质溶剂化模型 ( DFT/CM-MPB)对于固液界面双电层的研究,该方法能够计算双电层的平衡性质(零电荷电势和微分电容)和表面相图,在此基础上能深入研究基元反应的电荷转移系数,并结合微观动力学推导出宏观的Tafel(电流-电势)曲线. 并列举了该方法对于重要电化学反应(如氢电极反应)的应用实例.     

A simple Maxwell-Wagner-Butler-Volmer approach to the impedance of the hydrogen electrode in a nafion fuel cell

A simple one-dimensional model of the impedance of a hydrogen/Nafion electrode is set up combining the usual Maxwell-Wagner approach for linear, homogeneous, and isotropic media with the linearized Butler-Volmer equation for the interfacial, electrochemical reaction. Only one relaxation semicircle is normally seen in the Nyquist diagram, but a low-frequency arc may appear at high overvoltages. The model is described by only two dimensionless parameters (in addition to the dimensionless frequency). These parameters are related to the double-layer capacitance and to the interfacial electrochemical reaction rate, respectively. With some adjustments, the model can be used to explain the observed equilibrium impedance from 40 to 70 degrees C of a symmetric cell of the type C/Pt/H(2)|Nafion 117/H(2)/Pt/C. The hydrogen electrodes in this cell were built up as a disperse multiphase region (carbon, platinum grains, Nafion 117, and hydrogen gas) as commonly done in solid polymer fuel cells.     

An ac voltammetry study of Pt oxide growth

AC voltammetry of polycrystalline Pt in sulfuric acid solutions has been used to study the growth kinetics of the thin anodic Pt oxide film. Data were collected from 2 Hz to 50 kHz, one frequency per cycle, and were analyzed in the complex impedance plane. The faradaic process was modeled as a resistance parallel to the double-layer impedance, with a value approximately independent of potential in the do voltammetry plateau region. The equivalent circuit for the known growth law is derived and is shown to be a series RC combination. The capacitance was not detected but is expected to have a negligible effect in the measured frequency range. The value of the resistance found was consistent with the growth law found in other experiments. Evidence for additional faradaic elements in the equivalent circuit was inconclusive. We found no additional features in the impedance spectra at higher frequencies that could be associated with the fast electrosorption of OH suggested by other workers. The reversibility of the early stages of growth is therefore associated with structural reversibility rather than a fast process.     

A novel dual-impedance-analysis EQCM system--investigation of bovine serum albumin adsorption on gold and platinum electrode surfaces

Both quartz crystal micro-balance (QCM) impedance and electrochemical impedance spectroscopy (EIS) methods are widely used in interface studies. This paper presents details about a new strategy for simultaneous, mutual-interference-free and accurate measurements of QCM impedance and EI, through connecting a suitable capacitance in series with the piezoelectric quartz crystal (PQC) between QCM impedance and EIS measurement instruments. Combined and individual measurements of QCM impedance and EIS during silver deposition gave results comparable with each other, demonstrating the reliability of the proposed method. Bovine serum albumin (BSA) adsorption on gold and platinum electrodes in Britton-Robinson (B-R) buffers was investigated, and the Fe(CN)6(3-)/Fe(CN)6(4-) couple was used as an electrochemical probe to characterize BSA adsorption. While the reversibility of Fe(CN)6(3-)/Fe(CN)6(4-) couple on bare Au and Pt electrodes changed very slightly with decreasing solution pH from pH approximately 7 to pH approximately 2, the standard rate constant (ks) of this couple increased abruptly with solution pH below pH approximately 4.5 at a BSA-modified Au electrode, but decreased with solution pH at a BSA-modified Pt electrode. By analyzing the QCM impedance data with a modified BVD equivalent circuit and the EI data with a modified Randle's equivalent circuit, inflexion changes at pH approximately 4.5 were all found at pH-dependent responses of the resonant frequency, the double-layer capacitance, the capacitance of the adsorbed BSA layer, the peak-absorbance values of BSA solutions at 277.5 and 224.5 nm, and so on. It was also found that a BSA adsorption layer can effectively inhibit gold corrosion during ferrocyanide oxidation in a ferrocyanide-containing BR solution. Some preliminary explanations of these findings have been given. The proposed method is highly recommended for wider applications in surface science.     

Study of the adsorption of a hydrophobic peptide onto carbon surfaces by capacitance measurements

The adsorption of a hydrophobic peptide (β-CN (193–209)) onto glassy carbon and a carbon support of membrane was studied by double-layer capacitance measurements using electrochemical impedance spectroscopy (SIE). The kinetics of adsorption was investigated by recording the changes that occurred in the double-layer capacitance after adding the peptide. The change in capacitance was interpreted in terms of the number of close-contact areas between the peptide and the surface. A two-consecutive reaction model was used to describe peptide adsorption. The first step was attributed to the adsorption reaction itself and the second to a change in the conformation of the adsorbed peptide molecules. The corresponding theoretical equation of the variation of capacitance with time fits our results. Moreover, it allowed determination of the time constants for both reactions and three double-layer capacitances: the bare surface and the surfaces covered with monolayers of the peptide in states 1 and 2. For glassy carbon, the activation energies are 4.7 and 3.5 kJ mol⁻¹ for the first and second step of the reaction and the reaction orders are 0.64 and 0.35, respectively. These values are different for each step. This confirms the model of two separate reactions to describe adsorption. The first step comprises two elementary mechanisms. The first may correspond to the adsorption of the peptide onto the surface. The second may be consistent with a modification of the adsorbed molecules induced by the adsorption of other molecules over them. The second step of the process requires the contribution of peptides of the solution for it to occur. The changes in the double-layer capacitance depend on the peptide bulk concentration. This suggests that the peptide adsorbs in a different conformation depending on its bulk concentration. Peptide polymerisation could be responsible for this phenomenon.     

N80油套管钢应力状态下的CO2腐蚀行为研究

利用交流阻抗技术研究了拉伸、压缩和弯曲三种应力状态下N80油套管钢在饱和CO₂地层水中的腐蚀过程. 结果表明, 三种状态下的阳极电化学阻抗谱均出现了高频容抗弧、中低频感抗弧和低频容抗弧三个时间常数, 其中高频容抗弧与双电层电容和传递电阻有关, 感抗弧对应膜的活性溶解, 低频容抗弧与试样表面膜的生成有关. 随着三种状态下应变的增加, 感抗弧逐渐扩大, 而低频容抗弧则逐渐缩小, 表明应力状态下N80钢的CO₂腐蚀会加剧. 三种状态下的阴极阻抗谱高频均由容抗弧组成, 中低频由Warburg阻抗和容抗弧共同组成, 三种状态下随着应变程度的增加, Warburg阻抗增加, 反应电阻减小, 双电层电容减小, 说明应力会加速阴极反应过程的进行, 从而增加N80钢的CO₂腐蚀速率.     

Design of Micro‐interdigitated Electrodes and Detailed Impedance Data Analysis for Label‐free Biomarker Quantification

Electrical impedance based biosensing is a label‐free technique that is gaining momentum in biology/medicine. The electrical impedance, typically measured using an array of micro‐fabricated interdigitated electrode array (IDE), is a byproduct of the interaction between electric fields and target bio‐molecules/cells. In current impedance based biosensing, it has been focused on utilizing the magnitude of the impedance (|Z|) to detect/quantify bio‐molecules. There were no reports on designing IDE electrodes, sensitivity analysis and detailed impedance data analysis. To address this issue, we have designed and fabricated IDE array and performed model experiments. We have found that depending on the frequency of the external electric potential, there is a variation of electric field across the array of IDEs from first pair to last pair. We then developed impedance data analysis technique (using (|Z|) and its phase (φ)) to analyze the complex impedance data, and finally, we have utilized Warburg theoretical circuit model to calculate the capacitance and resistance of the individual IDE pairs in the constant phase impedance region. Using the capacitance values, we have developed a procedure to determine the sensitivity of the IDE array. We have found that sensitivity of the IDE array does not depend on the sample conductivity.     

Beta-phased Ni(OH)2 nanowall film with reversible capacitance higher than theoretical Faradic capacitance

β-Ni(OH)(2) was constructed into a three-dimensional mesoporous film on Ni foam with ultra-thin (～6 nm) primary nanowalls showing ultrahigh specific capacitance (2675 F g(-1)) and excellent cycling performance (>96% for 500 cycles). The capacitance was higher than theoretical value possibly due to the combination of Faradic and electrical double-layer capacitances.     

Double Layer at the Pt(111)–Aqueous Electrolyte Interface: Potential of Zero Charge and Anomalous Gouy–Chapman Screening

We report, for the first time, the observation of a Gouy–Chapman capacitance minimum at the potential of zero charge of the Pt(111)-aqueous perchlorate electrolyte interface. The potential of zero charge of 0.3 V vs. NHE agrees very well with earlier values obtained by different methods. The observation of the potential of zero charge of this interface requires a specific pH (pH 4) and anomalously low electrolyte concentrations (<10⁻³ m ). By comparison to gold and mercury double-layer data, we conclude that the diffuse double layer structure at the Pt(111)-electrolyte interface deviates significantly from the Gouy–Chapman theory in the sense that the electrostatic screening is much better than predicted by purely electrostatic mean-field Poisson–Boltzmann theory.     

稻壳多孔碳材料的电容性能及模型计算

采用NaOH和H₃PO₄化学活化法, 由廉价的稻壳制备了2种高比表面积的介孔活性碳, 测试了其比表面积和平均孔径, 利用循环伏安、 恒流充放电和交流阻抗测试了其电化学性能, 其比电容分别达到145.8和168.5 F/g. 利用一种多分支的三级孔道模型对其进行交流阻抗谱拟合, 拟合结果符合度较高, 表明该模型对分析活性碳电极结构有一定指导意义.