Electrochemical Impedance Method Research Articles

Preparing ultra-thin nano-MnO 2 electrodes using computer jet-printing method

Computer jet-printing method was developed to prepare ultra-thin film nano-MnO 2 electrodes using a computer with a jetprinter. Special emulsion ink containing nano-MnO 2 particles was jet-printed on the gold covered paper to form a thin film electrode. Scanning electron microscopy (SEM), voltammetry and electrochemical impedance methods were used to investigate the morphologies and electrochemical properties of electrodes. It is found that the discharge capacity of nano-MnO 2 film is 270 mAh/g at a current density of 4.01 A/g. This method shows the advantages of convenience, easy duplication, low cost for fabricating ultra-thin film electrodes, and can be used for manufacturing ultra-thin film batteries.

Understanding the Degradation of Organic Coatings Using Local Electrochemical Impedance Methods : I. Commonly Observed Features

Local electrochemical impedance mapping (LEIM) was used to investigate local underfilm corrosion occurring on organic-coated AA2024-T3 exposed to chloride solution. Films (5-20 μm thick) of neat epoxy, polyurethane, and vinyl resins were studied. Frequently observed features in the LEI maps included: an unexpected decrease in admittance in early stages of development, trenching at the periphery of admittance peaks, both increases and decreases in peak height over time, changes in peak width over time, different amplitudes in admittance over different regions of multilobed blisters, and different admittance magnitudes for different types of defect. These LEIM features could provide significant insight into and documentation of the local breakdown processes of coated metals, if they truly represent electrochemical phenomena associated with changes at the interface. These features were observed on each of the coating chemistries studied. Proposed origins and supportive evidence of these LEIM features is presented. © 2003 The Electrochemical Society. All rights reserved.

Peculiarities of Electrochemical Behavior of CsHSO4–SnO2 Composite System

Dependence of electronic and ionic components of conductance of CsHSO4–SnO2 systems on their composition is studied using the method of electrochemical impedance. The total electronic and ionic components of conductance nonmonotonically depend on the composition. To describe completely impedance diagrams of composite materials, an equivalent electrical circuit is proposed, which contains the bulk ionic conductance corresponding to the bulk of CsHSO4 grains, and the conductance corresponding to the surface of tin dioxide grains. Each conductance component is separated out. The activation energies for the bulk and surface conduction equal 0.32 ± 0.02 and 0.36 ± 0.02 eV, respectively, and are independent of the system composition. The bulk ionic conductance monotonically decreases with increasing SnO2 content and is well described wit percolation theory, whereas dependences of surface ionic and total electronic components have extremums.

Towards reversibility of ion transfer across the interface between valinomycin membranes and aqueous electrolyte solutions

Valinomycin-based potassium-selective membranes doped with potassium tetrakis(4-chlorophenyl)borate (KClTPB) or sodium tetrakis(4-fluorophenyl)borate (NaFTPB) are studied in KCl, NaCl, and CaCl2 solutions by potentiometric and electrochemical impedance methods. Before contact with KCl, membranes doped with NaFTPB provide Nernstian potentiometric response to Na+ ions, which is lost after conditioning the membranes in KCl. The membranes doped with KClTPB even before contact with KCl give no Nernstian response to Na+ ions. In CaCl2 solutions, none of the membranes provide a regular potentiometric response. Despite the difference in potentiometric behavior, the impedance spectra of the membranes are very similar in all solutions regardless of prior conditioning of the membranes. No evidence for a hindrance towards charge transfer processes is observed. The results suggest that the membrane/solution interface is reversible for interfering ions as well as for potassium, and the contamination of solutions with the latter is the sole reason for the lack of Nernstian response in the interfering electrolytes.

Electrochemical Impedance Characteristics of Some Medium Temperature Semicells for SOFC

Electrochemical characteristics of the semicells Ce 0.83 Gd 0.17 O 1.9 La 0.6 Sr 0.4 CoO 3-δ ; Ce 0.8 Sm 0.2 O 1.9 | La 0.6 Sr 0.4 CoO 3-δ and Ce 0.83 Gd 0.17 O 1.9 La 0.6 Sr 0.4 CoO 3-δ -Ag clusters have been studied by electrochemical impedance and chronoamperometric methods at various electrode polarisations ΔE and temperatures T. The polarisation resistance values, depending on ΔE and T, have been established from the electrochemical impedance data. The activation energy has been found to decrease slightly with the increase of |-ΔE|. The cathode reaction charge transfer coefficient α c ≃ 1.0 has been obtained from the Tafel-like overvoltage η c , logi-plots at T>823K, indicating the mass transfer limited process in the cathode material. The Z,Z'-plots have a complicated shape, and at least two time-constant values (two limiting stages) can be obtained. Thus, the kinetically mixed process, characterised by the slow transfer of electron to O ads and the diffusion-like step of O ads in the cathode material, is possible.

Study of surfactant adsorption onto electropolymerized o-phenylenediamine film by using a capacitive sensing method

A capacitive sensing device has been designed by using electropolymerized o-phenylenediamine (PPD) film as an isolating layer and has been applied successfully to study the adsorption of Tween 80 onto the PPD film surface. The PPD was prepared with a cyclic voltammetry method and the thickness of the PPD film was estimated as about 110 ± 10 nm. The properties of the PPD insulating film were characterized with an electrochemical impedance method. The results show that the equivalent circuit model of this device is Randles type. The adsorption process of Tween 80 onto the PPD film was detected with the electrochemical impedance method. The result implies that the adsorption model of Tween 80 onto the PPD film appeared as pseudo Langmuir type and the adsorption equilibrium constant was 213.87 (dm3 g−1). We expect that the capacitive sensor will be a useful tool for investigation of interface action.

Diffusion Conductivity of Electrode Processes under Conditions of Natural Convection

The diffusion conduction σ = di /dη (where i is the current and η is the overvoltage) in reversible system [Fe(CN)6]3–/4– is measured by the electrochemical impedance method under isothermal and nonisothermal conditions of natural convection. Platinum disk electrodes 3 mm and 20 μm in diameter are used. For a macroelectrode under isothermal conditions, σ passes through a maximum near equilibrium and tends to zero at η → 0. Under nonisothermal conditions and for a microelectrode under isothermal conditions, σ achieves a maximum near equilibrium. These data correlate with the η dependence of the diffusion layer thickness and quantitatively agree with theory.

Application of electrochemical impedance method to studying corrosion of porous powder steels

Electrochemical impedance spectroscopy (104–10–3 Hz) and weighing methods are applied to studying the corrosion behavior of powder austenitic 316L stainless steel with a porosity e = 15, 20, and 38% and compact steel of the same composition in a 3% HCl + 5% NaCl solution and oil pool water (pH 6.0; total mineralization 184.8 g/l, preferentially chlorides of Na, Ca, and Mg). Hodographs and phase angles of the electrode impedance are analyzed for high ac frequencies. The procedure of corrosion rate determination for powder steel from impedance data is described. The corrosion rate of powder steel calculated to the geometric surface area of a sample is shown to increase in acid and neutral chloride solutions with an increase in the porosity of samples from 15 to 38%, and, at e ≤ 20%, with the exposure of samples to the electrolytes (from 2 to 120 h). Advantages of the impedance method over the weighing method are demonstrated for determination of the corrosion rate of porous powder steels. Based on impedance measurements, the specific surface areas of powder steel samples are assessed.

Study on corrosion inhibitor in large pipelines under multiphase flow using EIS

An imidazoline based inhibitor behavior in carbon dioxide environment has been studied in large pipelines under different slug flow conditions by electrochemical impedance method. It is found that, for each of the slug flow condition, charge transfer resistance, R t, and Warburg impedance coefficient, σ, increase with increasing exposure time. It is suggested that the performance of the corrosion inhibitor is dependent on exposure time. The corrosion inhibitor has a good performance of corrosion protection by forming more compact inhibitor films on the metal surface at longer exposure time. Experimental results also show that, at a given time, both R t and σ decrease with increasing the Froude number of slug flow. This fact implies that the inhibitor film is damaged and washed away from the metal surface by high turbulence and the higher frequency of bubble pulse in high Froude number of slug flow, thus leading to low corrosion resistance.

Incentives for using local electrochemical impedance methods in the investigation of organic coatings

The assessment of changes in organic coatings in a corrosive environment has traditionally utilized global electrochemical methods, such as electrochemical impedance spectroscopy (EIS), in which a relatively large area of the sample is examined. Recently, more localized methods of impedance measurement have been developed and used to map heterogeneities across a sample surface, and the temporal changes of these regions. These localized methods are essential to further understand the breakdown process of coated alloys that inevitably occurs at discrete sites. This paper will examine the incentives for making local electrochemical impedance measurements, the advantages and limitations of this method, some of the lessons learned, and the present understanding of local breakdown processes on model-coated substrates.

Interpretation of Electrochemical Noise Data

Abstract The measurement of the electrochemical noise associated with corroding metals places a number of requirements on the measurement system if good quality data are to be obtained. In particular, aliasing and quantization noise should be avoided. Analysis methods may ignore the ordering of the measured potential or current values by using sequence-independent parameters such as the mean, standard deviation, skew, and kurtosis, or they may take the sequencing into account by computing the autocorrelation function, power spectra, or higher-order spectra. When potential and current noise are measured simultaneously, additional methods are available, including the calculation of electrochemical noise resistance, electrochemical noise impedance, characteristic charge, characteristic frequency, and various cross-correlation methods. Newer, somewhat more speculative methods include wavelet and chaos analysis. One of the most attractive prospects of electrochemical noise measurement methods is the ability to...

Impedance of Magnetite-Coated Steel Electrodes

Steel electrodes coated with magnetite of different defectiveness are studied by the electrochemical impedance method. In a borate buffer, the impedance is adequately described by an equivalent circuit for a passive steel electrode. The magnetite coating defectiveness can be evaluated from the frequency peak shift in a Bode diagram.

Corrosion behaviour of Monel in phosphoric acid

Nickel alloys are widely used as constructional materials in chemical processing industries. They are very resistant to pitting and crevice corrosion. In the present work, the corrosion behaviour of Monel in phosphoric acid of different concentrations has been studied by weight loss and electrochemical methods. It has been observed from the polarization studies that the passivation range slightly varies with H3PO4 concentration. The nature of the passive film has been investigated using the electrochemical impedance method.

Study of corrosion resistance property and microstructure of TiNi shape memory alloy modified by pulsed high-energy density plasma

The corrosion resistance of TiNi (Ti–50 at.% Ni) shape memory alloy is improved by about one order of magnitude after the surface is modified by pulsed high-energy density plasma (PHEDP) composed of titanium and nitrogen. The corrosion resistance property was measured by potentiodynamic polarization and electrochemical impedance methods in 2% sodium chloride (NaCl) and 0.5 mol l −1 H 2SO 4 solutions. The microstructure of the film is examined by transmission electron microscopy (TEM), which showed that the film is composed of TiN and Ti 2N phases. In the PHEDP surface modification, the effects of ion implanting combined with melting and rapid quenching contribute to the formation of nanocrystalline structure of TiN, which is the main reason for the corrosion resistance improvement of TiNi alloy. The existence of the transition area contributes to the adhesive strength between the film and the substrate. The unique shape memory effect of TiNi alloy is least affected by the PHEDP surface-coating technique.

Photoelectrochemistry as a novel strategy for DNA hybridization detection

The special properties of ssDNA and dsDNA molecules in structure and electric behavior, may offer us some new ideas for the fabrication of genosensors and DNA-chips. In this work, the photoelectrochemical method was firstly employed to characterize the photoelectric behavior of a ssDNA probe electrode, which was prepared with the self-assembly technique, and its resulting dsDNA electrode. The obvious decrease in the photocurrent of the dsDNA modified electrode at open potential or a bias voltage indicated that photoelectrochemistry was another useful method for DNA hybridization detection. Using the special design of ssDNA probes, we attempt to discuss further the relationship between the properties of DNA molecules and their photoelectric behaviors. In addition, the electrochemical impedance method was employed to verify the occurrence of some modifications over the electrode interface before and after the hybridization event.

The Detection and Mapping of Defects in Organic Coatings Using Local Electrochemical Impedance Methods

Corrosion failure in most organic coating/substrate systems initiates as a local event that may originate at a chemical or physical heterogeneity within the coating itself or possibly in the substrate. The ability to detect, map the location, and make quantitative in situ measurements of coating heterogeneities will help identify the source of failure (i.e., coating chemistry, method of application, cure schedule, etc.) and provide insight into the mechanisms of coating degradation. This study examines the efficacy of local electrochemical impedance mapping/spectroscopy for the examination of local corrosion events on coated steel substrates. Various types of intentional local heterogeneities were successfully detected with a five‐electrode system that utilizes a split microreference electrode. These heterogeneities included chemical defects within the coating such as absorbed oil and physical defects such as subsurface bubbles, underfilm salt deposits, pinholes, and directional underfilm corrosion. © 1999 The Electrochemical Society. All rights reserved.

電気化学インピーダンススペクトロスコピー (EIS) の理論と解析の基礎

Electrochemical Impedance Spectroscopy (EIS) has been known as a powerful tool for analyzing electrode reaction mechanism. In this review the history of EIS, the definition of electrochemical impedance, the general concept of transfer function, and the measurement method of electrochemical impedance using a transfer function analyzer are first introduced. Then, analytical methods of impedance spectra using electrical equivalent circuits and the kinetic theory of electrochemical reactions are stated. Finally, the future scope of EIS is briefly given.

電気化学的インピーダンスの測定とその解釈

The instrument and experimental method of electrochemical impedance were described. The simple criteria to select the Nyquist plot or Bode plot was revealed. Some equivalent circuits were presented and its analytical procedure was shown. The physical meaning of inductive behavior was explained by the calculation of Faradaic impedance. Finally, the 3-D plot (real, imaginary and time axes) to compensate the impedance, which does not have time stability, was introduced.

Investigations of Reversible and Polarised Interfacial Surface Properties by Electrochemical Impedance Method

The article concerns measuring the impedance of blocking Pt, Au, Ni, Ti and reversible Ag and Ag 2 Te electrodes on the interface with superionic conductor. Infralow frequency dependences of impedance module are described by fractional-order frequency dependence, the phase angle being constant in a definite frequency range, thus constant phase angle element (CPE) peculiarities reveal. The impedance characteristics under the alternation of electrode potential, formation pressure and temperature have been obtained. Algorithms of constructing the electrical models of metalsuperionic conductor interface, whose impedance is described by CPE-element [1-5] have been considered. The possibility of presenting the interface equivalent electrical circuits as Foster's canonical RC-circuits and realizing the impedance and admittance frequency characteristics with necessary precision in the given frequency range under random fractional parameters α in 0-1 interval has been demonstrated.

Electrochemical and Morphologic Investigation of Al-Mg-Zn Alloys in Artificial Sea Water

The surface activity of aluminium alloys in artificial sea water has been studied using electrochemical testing methods Electrochemical Impedance Spectroscopy (EIS), polarisation curves and electrode potential versus time measurements have been employed to study the main features of the processes taking place at the alloy/solution interface. The results obtained were discussed in terms of morphological structure and surface electrochemical behaviour correlation. The knowledge of the surface composition and the morphological structure has been performed using Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (EDXS). The Al-Mg-Zn alloys have been prepared using metals of high purity. The methodology of preparation allows the formation of intermetallic phases which strongly influence the anodic behaviour of aluminium.