固体氧化物燃料电池电化学阻抗谱差异化研究方法和分解

电化学阻抗谱技术(EIS)在固体氧化物燃料电池(SOFC)中已获得广泛应用。在EIS分析过程中,研究者能够清楚地获得燃料电池内部因纯离子(电子)导电引起的欧姆电阻和因电化学过程、扩散作用引起的极化阻抗的大小,但是对于极化阻抗的构成缺乏进一步解析。本文选用传统的Ni-YSZ阳极支撑电池,通过改变测试温度、阳极运行气氛和阴极运行气氛,设计了一套完整的阻抗差异分析(ADIS)实验。并基于弛豫时间分布法(DRT)和阻抗差异分析法,系统地分析并解释了阻抗谱中各频率段对应阻抗的物理或(电)化学含义,将该类型电池阻抗谱以6个RQ并联电路予以拟合,为之后燃料电池性能稳定性的研究奠定基础。     

镍电极在硼砂-硼酸缓冲溶液中的钝化和点蚀

近年来交流阻抗技术用于研究局部腐蚀,尤其在点蚀方面,引起了很大兴趣。Mansfeld等人和Oltra等人都提出了电极在点蚀时的等效电路.有关镍电极在Cl~-存在时的点蚀研究有过许多报导,但是至今尚未见到用交流阻抗技术研究Ni电极的点蚀.本文用交流阻抗技术对Ni电极在Na_2SO_4硼砂-硼酸缓冲溶液(pH8.4)中的钝化行为和Cl~-存在时的点蚀行为进行了研究,探讨了钝化和点蚀的规律和机理。     

多壁纳米碳管空气电极的交流阻抗研究

研究了多壁纳米碳管、活性炭和石墨等空气电极的交流阻抗特性.结果表明,纳米碳管空气电极的阻抗谱由两个半圆组成,高频区半圆对应欧姆极化阻抗,低频区半圆对应电化学极化阻抗.催化剂Pt以纳米颗粒的形式沉积在碳管的外表面,明显减小了电极的欧姆阻抗和电化学极化阻抗,提高了氧还原反应的电催化活性.活性炭电极除存在电化学阻抗外,还存在薄液膜扩散阻抗(Nernst扩散),石墨电极形成的薄液膜反应区域较小,电极反应呈Warburg扩散阻抗特征,相应的电催化活性较低.采用交流阻抗等效电路分析方法,对拟合的动力学数据进行了解释.     

示波极谱图的伸缩及位移

利用示波极谱图的伸缩或位移指示滴定终点是示波极谱滴定的一种新技术.本文全面探讨了示波极谱图伸缩及位移的原理,并用实验作了对照,理论计算与实验结果一致.伸缩来源于电极阻抗的变化,位移则主要由动力学因素引起.     

电化学石英晶体阻抗系统研究金电极上Fe(CN)3-6/Fe(CN)4-6电化学过程

电化学过程的石英晶体阻抗分析法已用于现场获取电活性聚合物粘弹性等信息[1,2]. 本文联用HP 4395A阻抗/网络/频谱分析仪和EG & G M283恒电位仪开发出电化学石英晶体阻抗系统(Electrochemical Quartz Crystal Impedance System, EQCIS), 适当条件下该系统能以小于1 s的时间间隔现场记录电化学过程的石英晶体阻抗数据. 测定了Na2SO4水溶液中石英晶体金电极上K3Fe(CN)6/K4Fe(CN)6电化学过程的等效电路参数. 结果表明, 扩散层内的密度和粘度变化引起动态电阻对电位的可逆变化, 而各谐振频率的变化为密度、粘度变化和阳极过程中K3Fe(CN)6溶液腐蚀金电极的加合结果.     

毛细管的交流阻抗特性研究

采用交流阻抗法研究了电容耦合非接触电导检测池毛细管的阻抗特性,分别考察了电极连接方式和毛细管内径对检测池阻抗的影响.实验表明:高频时,除去毛细管外层保护层会使检测池的阻抗减小,有助于检测器灵敏度的提高;采用铜箔作电极能够有效地消除电极与毛细管壁之间的空隙,使得检测池在低频时阻抗减小.随着毛细管内径的变大,阻抗依次减小.通过Zview软件拟合,提出的简单的拟合等效电路为R(RC)CPE.     

环氧树脂涂覆LY12铝合金在NaCl溶液中的阻抗模型

分别研究了裸LY12铝合金及涂覆环氧树脂涂层后合金在3.5％NaCl溶液中的电化学阻抗谱（EIS）.结果表明,LY12铝合金在点蚀电位以下阻抗谱上出现两个容抗弧,高频段对应Cl－参与的成膜阻抗,低频段对应铝阳极溶解的电化学反应阻抗.合金发生点蚀后出现低频感抗弧.合金/电极在NaCl溶液中先发生涂层吸水,当水及O2抵达基体后建立起电化学反应界面,合金遭受腐蚀；受涂层阻挡的影响,腐蚀产物的扩散逐渐成为控制步骤；当扩散速度较慢的Cl－抵达涂层/金属界面后,与界面处聚集的腐蚀产物间发生化学反应,完成成膜过程,阻抗谱上出现盐膜的阻抗,而扩散阻抗消失.提出了不同浸泡失效阶段涂层电极体系的阻抗模型.     

电化学阻抗谱法测定固态聚合物电解质的本体电阻

采用电化学阻抗谱法,对阻抗谱中的聚合物电解质本体电阻（Rb）与膜厚（L）的关系和固体聚合物电解质/惰性电极间的界面阻抗随直流电压的变化趋势进行了研究.结果表明,阻抗谱中聚合物电解质本体电阻（Rb）含有一定的阻塞电极/聚合物电解质间的界面阻抗;由于界面双电层电容的变化,在直流电压0.15～3 V范围内,界面阻抗随电压的增大而减小.     

Li/SOCl_2、BCX电池放电电压滞后研究

应用交流阻抗法研究Li/SOCl2、BCX电池放电过程碳、锂电极阻抗变化并测试外加电压和并联超电容对电池放电初期电压的影响.测试表明,锂电极阻抗在放电初期迅速减小了80%~90%,直到放电末期,阻抗几乎不变;碳电极阻抗至放电末期才迅速增大;BCX电池有较高开路电压可改善放电电压滞后;电池并联超级电容器可抑制放电电压滞后.     

一些电化学交流阻抗复数平面图旋转的物理意义

本文讨论了电化学交流阻抗图中图形旋转的物理意义.电化学体系等效电路中的电容基本上属复数电容,由此推导出在这个假设下的阻抗极坐标公式,及其参数的数学表达式.实际上此表达式与很多电化学体系的实际阻抗谱相符,如:实际测量的理想极化电极的阻抗图并不是平行于虚轴的一条直线,而是其与实轴的交点顺时钟旋转了α角的直线,这时,即双层电容的耗散角;与RC并联电路有关的半圆阻抗图几乎都有同一方向的α角旋转,其值等于相关电容的耗散角.若明确了旋转的物理意义,由电化学阻抗谱拟合得到的参数均可表征体系的性质,这对于寻求某些特殊性能的电池体系将是有用的.     

Characterization of Electrode/Electrolyte Interface of ECIS Devices

Electric cell‐substrate impedance sensing requires low electrode/electrolyte interface impedance for effective biomedical and biophysical applications. Thus a complete understanding of physical processes involved in the formation of an electric double layer is required to design a low interface impedance device. This paper presents the numerical simulation of the impedance for the electrode/electrolyte interface of three‐electrode devices along with the practical realization for the effective workout of impedance sensing devices. The three‐electrode based impedance sensing devices along with phosphate buffered saline as electrolyte is simulated using COMSOL Multiphysics to evaluate the impedance of the electrode/electrolyte interface. Microfabrication technology is used to realize three‐electrode impedance sensing devices with diverse configuration which are used to measure the electrode/electrolyte interface impedance. The measured impedance data were then compared with the COMSOL simulated results and it is found that both the data sets fitted well with less than 5 % RSE. The results obtained from simulation and experiments indicate that the impedance due to double layer diffusion dominates in the low frequency region up to few kHz whereas electrolytic bulk resistance plays a major role in the higher frequency range. The experimental impedance data were further interpreted by electrochemical impedance spectroscopy analysis software to model the equivalent circuit of the electrochemical system.     

液/液界面的电化学阻抗谱测量Ⅰ: 四电极系统中各类界面阻抗的分析

本文系统地研究了将阻抗谱技术应用于液/液界面电化学领域时所出现的问题。提出了四电极系统中液/液界面交流阻抗的表达式。从理论上分析了电解池参数和仪器输入参数对所得交流阻抗曲线的影响。     

Impedance methods for electrochemical sensors using nanomaterials

This article presents an overview of electrochemical sensors that employ nanomaterials and utilize electrochemical impedance spectroscopy for analyte detection. The most widely utilized nanomaterials in impedance sensors are gold (Au) nanoparticles and carbon nanotubes (CNTs). Au nanoparticles have been employed in impedance sensors to form electrodes from nanoparticle ensembles and to amplify impedance signals by forming nanoparticle-biomolecule conjugates in the solution phase. CNTs have been employed for impedance sensors within composite electrodes and as nanoelectrode arrays. The advantages of nanomaterials in impedance sensors include increased sensor surface area, electrical conductivity and connectivity, chemical accessibility and electrocatalysis.     

Electrochemical Impedance of Ethanol Oxidation in Alkaline Media

Nickel modified NiOOH electrodes were used for the electrocatalytic oxidation of ethanol in alkaline solutions. The electro-oxidation of ethanol in a 1 mol/L NaOH solution at different concentrations of ethanol was studied by ac impedance spectroscopy. Electrooxidation of ethanol on Ni shows negative resistance on impedance plots. The impedance shows different patterns at different applied anodic potential. The influence of the electrode potential on impedance was studied and a quantitative explanation for the impedance of ethanol oxidation was given by means of a proposed mathematical model. At potentials higher than 0.52 V(vs. Ag/AgCl), a pseudoinductive behavior was observed, but at those higher than 0.57 V, impedance patterns were reversed to the second and third quadrants. The conditions required for the reversing of impedance pattern were delineated with the impedance model.     

Electrical impedance spectroscopy for detection of bacterial cells in suspensions using interdigitated microelectrodes

In this study, we present a new, simple and rapid impedance method to detect bacterial cells by making use of the impedance properties of bacterial cell suspensions using interdigitated microelectrodes. It was found that bacterial cell suspensions in deionized (DI) water with different cell concentrations could generate different electrical impedance spectral responses, whereas cell suspensions in phosphate buffered saline (PBS) solution could not produce any significant differences in impedance spectra in response to different cell concentrations. In DI water suspensions, impedance at 1 kHz decreased with the increasing cell concentrations in the suspensions. The impedance of cell suspensions in DI water was discussed and found that it was resulted from the cell wall charges and the release of ions or other osmolytes from the cells. A linear relationship between the impedance and the logarithmic value of the cell concentration was found in the cell concentration range from 10⁶ to 10¹⁰ cfu/ml, which can be expressed by a regression equation of Z (kΩ) = −2.06 log C (cells/20 μl) + 5.23 with R² = 0.98. The detection limit was calculated to be 3.45 × 10⁶ cfu/ml, which is comparable with many label-free immunosensors for detection of pathogenic bacteria reported in the literature. To achieve the selectivity of this method, we also demonstrated the feasibility of integrating magnetic separation to this impedance method. This study has demonstrated that bacterial cell concentration can be inferred by measuring the impedance of cell suspensions in DI water. This new detection mechanism could be an alternative to current impedance methods that have been reported for the detection of bacterial cells, e.g. impedance microbiology and electrical/electrochemical impedance biosensors.     

Analysis of electrochemical impedance spectra of anodised pure aluminium foil with various etch tunnel length distributions used for electrolytic capacitors

The present work analyses the electrochemical impedance spectra of anodized pure Al foil with various etch tunnel length distributions, used for electrolytic capacitors. The lengths of the etch tunnels formed on the Al foil specimen were more widely distributed with increasing etching time. The etch tunnel length distributions were quantitatively measured by scanning electron microscopy. All the measured impedance spectra hardly exhibited the ideal capacitive behaviour in the high-frequency region and they deviated more significantly from the ideal capacitive behaviour with increasing etching time. For the numerical calculation of the total impedance of the electrode, the transmission line model was modified to reflect the etch tunnel length distribution, which represents the respective contributions of etch tunnels with different lengths to the total impedance. The total impedance was calculated by the integration of the impedance of one etch tunnel with respect to the etch tunnel length by taking the value of the etch tunnel length distribution determined experimentally. From the coincidence of the impedance spectra calculated numerically with those spectra measured experimentally, it is concluded that the deviation of the impedance spectra from the ideal capacitive behaviour in the high-frequency region originates from the characteristic frequency dispersion that depends upon the etch tunnel length distribution.     

交流电解阻抗的数字模拟——Ⅰ.可逆、准可逆体系和薄层电解池的电解阻抗

本文用数字模拟方法研究了可逆、准可逆和不可逆电极反应的交流阻抗,得到了与理论推导相符合的结果。文中亦研究了薄层电解池的交流阻抗的数字模拟。通过数字模拟,人们不需用等效电路模型便能解释交流阻抗数据的化学意义,这对认识复杂电极过程尤为重要。文中给出了交流阻抗的离散数字模型,并讨论了动力学参数对阻抗数据的影响。     

Spatially resolved electrical impedance methods for cell and particle characterization

Electrical impedance is an established technique used for cell and particle characterization. The temporal and spectral resolution of electrical impedance have been used to resolve basic cell characteristics like size and type, as well as to determine cell viability and activity. Such electrical impedance measurements are typically performed across the entire sample volume and can only provide an overall indication concerning the properties and state of that sample. For the study of heterogeneous structures such as cell layers, biological tissue, or polydisperse particle mixtures, an overall measured impedance value can only provide limited information and can lead to data misinterpretation. For the investigation of localized sample properties in complex heterogeneous structures/mixtures, the addition of spatial resolution to impedance measurements is necessary. Several spatially resolved impedance measurement techniques have been developed and applied to cell and particle research, including electrical impedance tomography, scanning electrochemical microscopy, and microelectrode arrays. This review provides an overview of spatially resolved impedance measurement methods and assesses their applicability for cell and particle characterization.     

Technology of electrochemical impedance spectroscopy for an energy-sustainable society

Electrochemical impedance spectroscopy has been widely used to understand the chemistry and physics of battery systems. This review covers electrochemical impedance spectroscopy used for the interpretation of impedance data of lithium-ion batteries (LIBs) from advanced equivalent circuit models to the mathematical model, which is developed by John Newman. In addition, as a method to realize an energy-sustainable society using diagnostics based on the combination of LIBs and electrochemical impedance spectroscopy, on-board diagnostics of battery packs are achieved based on an input signal generated by a power controller in a battery management system instead of the conventionally used frequency response analyzer. The diagnostic system is applicable to energy management systems which are installed in homes, buildings, and communities, accumulating the impedance data on state of health of LIBs. Finally, a future possibility regarding the diagnostics of battery packs coupled with the machine learning of impedance data is introduced.     

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.