The key difference between polarizable and non polarizable electrode is that polarizable electrodes have a charge separation at the electrode-electrolyte boundary whereas non-polarizable electrodes have no charge separation at this electrode-electrolyte boundary.
Polarization of electrodes in electrochemistry refers to the reduction of the performance of a battery. It is a collective term that is used for certain mechanical side effects of electrochemical processes by which isolating barriers develop at the interface between electrode and electrolyte. These side effects can influence the reaction mechanism inside the battery as well as the chemical kinetics of corrosion and metal deposition. The major side effects include activation polarization and concentration polarization. Activation polarization refers to the accumulation of gases at the interface between electrode and electrolyte while concentration polarization refers to the uneven depletion of reagents in the electrolyte, causing a concentration gradient in boundary layers.
CONTENTS
1. Overview and Key Difference
2. What is a Polarizable Electrode
3. What is a Non Polarizable Electrode
4. Side by Side Comparison – Electrochemical Cell vs Galvanic Cell in Tabular Form
5. Summary
What is a Polarizable Electrode?
A polarizable electrode is an electrode in an electrochemical cell that is characterized by charge separation at the electrode-electrolyte boundary. We can observe that this type of polarizable electrode is electrically equivalent to a capacitor. An ideal polarizable electrode is a hypothetical substance that is characterized by the absence of a net DC current between the two sides of the electrical double layer. In other words, there is no faradic current existing between the electrode surface and the electrolyte. Therefore, any transient current that is flowing through this system is considered as non-faradic current.
Figure 01: Batteries: Small Electrochemical Cells with Electrodes
The behaviour of this type of an electrode is due to electrode reaction being infinitely slow, having a zero exchange current density, making it behave as a capacitor by means of electricity. The chemical concept on this polarizable electrode was developed by the scientist F.O.Koenig in 1934. The platinum electrode is a classic example of a polarizable electrode.
What is a Non Polarizable Electrode?
A non-polarizable electrode is an electrode in an electrochemical cell that can be characterized by no charge separation at the electrode-electrolyte boundary. That means the electrochemical cells having these electrodes have faradic current that can freely pass without polarization. An ideal non-polarizable electrode is a hypothetical electrode having this property of not having a charge separation. The potential of a non-polarizable electrode does not change from its equilibrium potential upon the application of a current. We can observe the reason for this behaviour as the infinitely fast electrode reaction that has an infinite exchange current density. This type of electrodes can behave as an electrical shot. Silver/silver chloride electrode is a classic example of a non-polarizable electrode.
What is the Difference Between Polarizable and Non Polarizable Electrode?
Polarizable and non-polarizable electrodes are the two major types of electrodes we can find in electrochemical cells. The key difference between polarizable and non polarizable electrode is that polarizable electrodes have a charge separation at the electrode-electrolyte boundary whereas non-polarizable electrodes have no charge separation at this electrode-electrolyte boundary.
Below infographic tabulates the differences between polarizable and non polarizable electrode in more detail.
Summary – Polarizable vs Non Polarizable Electrode
Polarizable and non-polarizable electrodes are the two major types of electrodes we can find in electrochemical cells. The key difference between polarizable and non polarizable electrode is that polarizable electrodes have a charge separation at the electrode-electrolyte boundary whereas non-polarizable electrodes have no charge separation at this electrode-electrolyte boundary.
Reference:
1. “ Polarizable Non-Polarizable Electrode.” Jyothi Engineering College – Slideshare, 11 July 2014. Available here.
Image Courtesy:
1. “Batteries Rechargeable Batteries Current Free Photo” (CC0) via Needpix