The Randles circuit is an equivalent circuit model commonly used in electrochemical impedance spectroscopy (EIS) to represent the impedance behavior of an electrochemical cell, particularly at an electrode/electrolyte interface. It provides a simplified but useful representation of the various components contributing to the overall impedance.
The basic Randles circuit consists of:
- Rs (Solution Resistance): Represents the resistance of the electrolyte solution between the working electrode and the reference electrode.
- Rct (Charge-Transfer Resistance): Represents the resistance to electron transfer at the electrode/electrolyte interface. It's related to the kinetics of the redox reaction.
- Cdl (Double-Layer Capacitance): Represents the capacitance of the electrical double layer formed at the electrode/electrolyte interface. This double layer arises from the accumulation of ions at the electrode surface.
- Zw (Warburg Impedance): Represents the diffusion-limited impedance that occurs when the redox reaction is controlled by the diffusion of electroactive species to the electrode surface.
These components are typically arranged as follows:
- Rs is in series with the parallel combination of Rct and Cdl.
- Zw is in series with Rct.
The Randles circuit allows researchers to:
- Model and interpret EIS data.
- Extract kinetic parameters, such as Rct, which provides information about the electron-transfer rate.
- Determine the double-layer capacitance, which is related to the electrode surface area and properties.
- Identify diffusion-limited processes.
It's a foundational tool in electrochemical analysis, helping to understand the fundamental processes occurring at electrode interfaces.
🧠Example - Randles circuit and impedance model
https://gist.github.com/viadean/ada70a5b17162af261bbee6aff92347e
Explanation:
- Simulated Data:
- Generates simulated impedance data for a Randles circuit using
impedance.models.circuits.Randles.
- Adds random noise to simulate real-world measurements.
- scikit-rf Network:
- Creates a
skrf.Network object to represent the impedance data, which provides convenient plotting and analysis functions.