What are Electrodes?

An electrode is made from conductive material that can transmit electricity. When an electric current is applied, the electrode facilitates the transfer of electrons, enabling electrical reactions. Electrodes exist as part of a circuit and are in contact with other parts of the system such as an electrolyte solution or air. They are used to:

• Measure electrical impulses in medical diagnostics.
• Facilitate electrochemical reactions in batteries.
• Emitting or collect electrons in electronic devices.

Electrodes are the sites of oxidation and reduction (redox) reactions within electrochemical cells. They can be classified as either an anode (-ve) or a cathode (+ve).

• Electrodes where oxidation occurs and electrons are emitted are anodes.
• Electrodes where reduction occurs and electrons are gained are cathodes.

What is a reference electrode?

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Reference electrodes have stable and well-defined electrochemical potential. The potential of other electrodes in the system can be controlled and measured based off these well-defined properties.

Reference electrodes are used in three electrode electrochemical systems to perform electrochemical methods. These include cyclic voltammetry or linear sweep voltammetry. Reference electrodes are sometimes referred to simply as 'the third electrode'.

The composition of a standard reference electrode should remain effectively unchanging and constant during electrochemical measurements. The purpose of the reference electrode is to provide a stable potential for controlled regulation of the working electrode potential. This allows the measurement of the potential at the working electrode without passing current through it.

An ideal reference electrode should also have zero impedance. This is determined by the resistance of its isolation junction.

What is a working electrode?

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The working electrode is where the electrically driven chemical reaction and electron transfer happens. This makes it one of the most important components within an electrochemical cell. The most commonly used materials are:

• Platinum
• Gold
• Carbon
• Mercury

Being electrochemically inert and easy to be fabricated into many forms, platinum is often preferred. Gold electrodes are less tolerant to oxidation in the positive potential range, but good to form self-assembled monolayer on its surface while carbon electrodes are more tolerant to more negative potentials.

What is a counter electrode?

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Counter Electrode

Counter electrodes are also referred to as auxiliary electrodes. They are used in two or three electrode systems along with reference and working electrodes. Counter electrodes provide or accept electrons in order to keep the system at a neutral charge. They do so without passing significant current through the reference electrode.

Counter electrodes are used complete the circuit so that electrochemical methods such as cyclic voltammetry and linear sweep voltammetry can be performed.

Counter electrodes are made from highly conductive and chemically stable materials such as:

• Platinum
• Graphite
• Gold
• Silver
• Stainless Steel

Electrodes

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