Electrochemical Impedance Spectroscopy Theory Research Articles

A Tutorial on Electrochemical Impedance Spectroscopy and Nanogap Electrodes for Biosensing Applications

Electrochemical Impedance Spectroscopy (EIS) is a powerful measurement technique used by scientists and engineers to characterize and understand the interfacial behavior of liquid-solid interfaces. Such investigations are important in numerous applications and fields of research, including electrochemical synthesis and deposition of materials, such as metals and conducting polymers, corrosion protection analysis, investigation of molecule-surface interactions, and research on batteries and fuel cells. In recent years, advances in nanotechnology have led to a rise in the use of EIS in chemical and bio-sensing. Areas such as molecular diagnostics and healthcare can greatly benefit from this novel technology, which includes low-cost, rapid response measurements that can be done by non-experts at the point of care. For new entrants, the depth of knowledge and breadth of EIS and its many applications can be rather daunting. This article therefore serves as a tutorial on basic EIS theory, whilst highlighting new applications in advanced bio-sensing. The tutorial begins with a theoretical overview, including electrical AC impedance, formation and structure of electrical double layers at liquid solid-interfaces and equivalent circuit models used to represent interfacial phenomena. This is followed by an introduction to bio-sensing and a review of recent research highlights on resistive and capacitive biosensors based on nanogap electrodes, especially those having novel applications from DNA detection to nanoparticle capturing. Lastly, the article highlights a recent new breakthrough on how the combination of nanogap electrodes with label-free methods, such as aptamer functionalized surfaces, can make capacitive sensors with extremely high sensitivity and specificity.

Variable-Order Equivalent Circuit Modeling and State of Charge Estimation of Lithium-Ion Battery Based on Electrochemical Impedance Spectroscopy

In the battery management system, it is important to accurately and efficiently estimate the state of charge (SOC) of lithium-ion batteries, which generally requires the establishment of a equivalent circuit model of the battery, whose accuracy and rationality play an important role in accurately estimating the state of lithium-ion batteries. The traditional single order equivalent circuit models do not take into account the changes of impedance spectrum under the action of multiple factors, nor do they take into account the balance of practicality and complexity of the model, resulting the low accuracy and poor practicability. In this paper, the theory of electrochemical impedance spectroscopy is used to guide and improve the equivalent circuit model. Based on the analysis of the variation of the high and intermediate frequency range of the impedance spectrum with the state of charge and temperature of the battery, a variable order equivalent model (VOEM) is proposed by Arrhenius equation and Bayesian information criterion (BIC), and the state equation and observation equation of VOEM are improved by autoregressive (AR) equations. Combined with the unscented Kalman filter (UKF), a SOC online estimation method is proposed, named VOEM-AR-UKF. The experimental results show that the proposed method has high accuracy and good adaptability.

Reducing the resistance for the use of electrochemical impedance spectroscopy analysis in materials chemistry.

Electrochemical impedance spectroscopy (EIS) is a highly applicable electrochemical, analytical, and non-invasive technique for materials characterization, which allows the user to evaluate the impact, efficiency, and magnitude of different components within an electrical circuit at a higher resolution than other common electrochemical techniques such as cyclic voltammetry (CV) or chronoamperometry. EIS can be used to study mechanisms of surface reactions, evaluate kinetics and mass transport, and study the level of corrosion on conductive materials, just to name a few. Therefore, this review demonstrates the scope of physical properties of the materials that can be studied using EIS, such as for characterization of supercapacitors, dye-sensitized solar cells (DSSCs), conductive coatings, sensors, self-assembled monolayers (SAMs), and other materials. This guide was created to support beginner and intermediate level researchers in EIS studies to inspire a wider application of this technique for materials characterization. In this work, we provide a summary of the essential background theory of EIS, including experimental design, signal responses, and instrumentation. Then, we discuss the main graphical representations for EIS data, including a scope of the foundation principles of Nyquist, Bode phase angle, Bode magnitude, capacitance and Randles plots, followed by detailed step-by-step explanations of the corresponding calculations that evolve from these graphs and direct examples from the literature highlighting practical applications of EIS for characterization of different types of materials. In addition, we discuss various applications of EIS technique for materials research.

Welcome Remarks - F02: Advances in Application and Theory of Electrochemical Impedance Spectroscopy

Welcome to F02: Advances in Application and Theory of Electrochemical Impedance Spectroscopy! Take a moment to listen to welcome remarks from the lead organizer, Mark Orazem.

In Ukrainian

A review of recent literature data on appearance of spontaneous oscillations in electrochemical systems of practical relevance is presented. They include electrocatalytic reactions of electrooxidation of hydrogen and small organic molecules on noble metals, oscillatory processes during preparation of different nanostructured materials such as nanotubes and multilayered structures, electrochemical systems with electrodissolution – passivation -electrodeposition of metals and alloys. Many of these systems belong to N-NDR or HN-NDR type of oscillator. They are investigated by different experimental techniques including electrochemical impedance spectroscopy, differential electrochemical mass spectroscopy, surface-enhanced infrared absorption spectroscopy, electrochemical quartz crystal microbalance/nanobalance, Auger electron analysis etc. It has been shown that electrochemical oscillations and more complex spatio-temporal surface structures in these systems are very sensitive to variation of experimental parameters such as applied potential, current density, solution concentration, structure and composition of electrode/electrolyte interface etc. The influence of these parameters on non-linear behavior of a model N-NDR electrochemical system was presented based on the theory of electrochemical impedance spectroscopy. An electrochemical reaction in the chosen model is related to the potential-dependent adsorption/desorption of electroactive particles on a planar, cylindrical or spherical interface and a preceding chemical reaction in the Nernst diffusion layer under potentiostatic conditions. The obtained results indicate that the range of Hopf instability giving rise to spontaneous oscillations in the system can be regulated by variation of electrode form and radius, thickness of the Nernst diffusion layer, diffusion coefficient of electroactive species, ohmic loses, bulk concentration of electroactive species. The role of mass transfer function in appearance of dynamic instabilities in the non-equilibrium system was determined.

Interpretation of electrochemical impedance spectroscopy (EIS) circuit model for soils

Based on three different kinds of conductive paths in microstructure of soil and theory of electrochemical impedance spectroscopy (EIS), an integrated equivalent circuit model and impedance formula for soils were proposed, which contain 6 meaningful resistance and reactance parameters. Considering the conductive properties of soils and dispersion effects, mathematical equations for impedance under various circuit models were deduced and studied. The mathematical expression presents two semicircles for theoretical EIS Nyquist spectrum, in which the center of one semicircle is degraded to simply the equivalent model. Based on the measured parameters of EIS Nyquist spectrum, meaningful soil parameters can easily be determined. Additionally, EIS was used to investigate the soil properties with different water contents along with the mathematical relationships and mechanism between the physical parameters and water content. Magnitude of the impedance decreases with the increase of testing frequency and water content for Bode graphs. The proposed model would help us to better understand the soil microstructure and properties and offer more reasonable explanations for EIS spectra.

Electrochemical impedance spectroscopy of hardened compacted cemented soils at early curing stage

Based on the theory of electrochemical impedance spectroscopy (EIS) and the properties of compacted cemented soils (CS) at different early curing time, an equivalent circuit model was developed to study the physical meanings of EIS parameters. EIS was also used to investigate the properties and hardened mechanisms of CS at different curing time. The relationships among the unconfined compressive strengths (UCS) of CS and EIS parameters are discussed. In addition, a useful multi-linear regression equation for UCS is proposed. The proposed model and EIS parameters help to understand the processing of cement hardened soils and the properties of CS. The study results offer more reasonable explanations for the EIS spectra.

Electrochemical Impedance Spectroscopy Investigation on the Clinical Lifetime of ProTaper Rotary File System

The main objective of the current paper is to show that electrochemical impedance spectroscopy (EIS) could be a method for evaluating and predicting of ProTaper rotary file system clinical lifespan. This particular aspect of everyday use of the endodontic files is of great importance in each dental practice and has profound clinical implications. The method used for quantification resides in the electrochemical impedance spectroscopy theory and has in its main focus the characteristics of the surface titanium oxide layer. This electrochemical technique has been adapted successfully to identify the quality of the Ni-Ti files oxide layer. The modification of this protective layer induces changes in corrosion behavior of the alloy modifying the impedance value of the file. In order to assess the method, 14 ProTaper sets utilized on different patients in a dental clinic have been submitted for testing using EIS. The information obtained in regard to the surface oxide layer has offered an indication of use and proves that the said layer evolves with each clinical application. The novelty of this research is related to an electrochemical technique successfully adapted for Ni-Ti file investigation and correlation with surface and clinical aspects.

On-line supercapacitor dynamic models for energy conversion and management

This paper develops on-line nonlinear dynamic models of electrochemical supercapacitors which are for energy conversion and management. Based on the theory of electrochemical impedance spectroscopy, extensive alternative current impedance tests have been conducted to investigate the frequency-domain dynamics of these supercapacitors. A Nyquist diagram is plotted to help establish an equivalent electric circuit, which is regarded as the first-phase linear model. Two performance-influencing factors, environmental temperature and operating voltage, are considered as nonlinear effects. The nonlinear relationships among parameters of the capacitances and resistances in the first-phase model are established by a multi-layer artificial neural network. The neural parameters are trained using a back-propagation algorithm by feeding the experimental data bank. Combining the first-phase model and the on-line neural “parameter identifier”, the algorithm produces an on-line nonlinear dynamic model. Simulation results have proved that this proposed model is able to achieve both system fidelity and computational efficiency.

The Use of Electrochemical Impedance Spectroscopy in the Evaluation of Coatings for Outdoor Bronze

Electrochemical impedance spectroscopy (EIS) is a technique that quantitatively measures the amount of corrosion protection provided by a coating to a metal substrate. This article illustrates the theory of EIS along with its potential for application in the evaluation of protective coatings for outdoor bronze sculpture and ornamentation. Three coating systems were evaluated on a monumental cast bronze: a microcrystalline wax; the methyl methacrylate copolymer sold under the trade name Incralac; and an acrylic/acrylic urethane topcoat. Each coating system was aged using accelerated weathering and evaluated via EIS. This information was then used to calculate the impedance modulus of the samples, which is displayed in Bode plots and interpreted in terms of coating performance.

Hydrogen insertion reaction with restricted diffusion. Part 1. Potential step—EIS theory and review for the direct insertion mechanism

Electrochemical impedance spectroscopy (EIS) theory is presented for the direct hydrogen insertion reaction with restricted diffusion. The limiting shapes of the Nyquist impedance plots are given and the changes in the impedance diagrams due to the double-layer capacitance are presented. The responses to small potential steps are also considered. All the limiting expressions for the current transients are given and a kinetic zone diagram is plotted in the time domain to determine the conditions of validity of these expressions. The correspondences between EIS diagrams and current transients due to small potential steps are shown. The results obtained for small potential steps are finally generalized to large steps when a Langmuir insertion isotherm is considered and the hydrogen diffusion coefficient is assumed to be constant.