EIS data are generally analyzed in terms of an equivalent-circuit model. The analyst tries to find a model whose impedance matches the measured data. The type of electrical components in… read more →
A metal covered with an undamaged coating generally has a very high impedance. The equivalent circuit for a scenario like this includes a resistor (primarily caused by the electrolyte) and… read more →
The Randles cell is one of the simplest and most common cell models. It includes a solution resistance, a double-layer capacitor and a charge-transfer or polarization resistance. In addition to… read more →
First consider a cell where semi-infinite diffusion is the rate-determining step, with a series solution resistance as the only other cell impedance. A Nyquist plot for this cell is shown… read more →
In the following help sessions we show some common models for equivalent circuits. These models can be used to interpret simple EIS data. Many of these models have been included… read more →
The equivalent-circuit elements that can be used in the Modeler are shown below. Equations for both the admittance and impedance are given for each element. Symbol Circuit Element (alphabetical symbol)… read more →
The impedance of an electrochemical cell can also appear to be inductive. Some authors have ascribed inductive behavior to adsorbed reactants. Both the adsorption process and the electrochemical reaction are… read more →
Solution resistance is often a significant factor in the impedance of an electrochemical cell. A modern three-electrode potentiostat compensates for the solution resistance between the counter and reference electrodes. However,… read more →
Whenever the potential of an electrode is forced away from its value at open circuit, this is called polarizing the electrode. When an electrode is polarized, it can cause current… read more →
Diffusion can create an impedance known as the Warburg impedance, which depends on the frequency of the potential perturbation. At high frequencies the Warburg impedance is small because diffusing reactants… read more →