What are Cathode and Anode?
Let us understand what cathode and anode exactly mean. They are both defined by the flow of current. Therefore, a cathode is an electrode from which the current exits a polarized electrical device.
Likewise, an anode is an electrode from which a current enters into a polarized electrical device.
The terms were finalized in 1834 by William Whewell who adapted the words from the Greek word (kathodos), ‘descent’ or ‘way down’. William had consulted with Michael Faraday for the coining of the terms.
Cathode
When we talk about cathode in chemistry, it is said to be the electrode where reduction occurs. This is common in an electrochemical cell. Here, the cathode is negative as the electrical energy that is supplied to the cell results in the decomposition of chemical compounds. However, it can also be positive as in the case of a galvanic cell where a chemical reaction leads to the generation of electrical energy.
In addition, a cathode is said to be either a hot cathode or a cold cathode. A cathode which is heated in the presence of a filament to emit electrons by thermionic emission is known as a hot cathode whereas cold cathodes are not heated by any filament. A cathode is usually flagged as “cold” if it emits more electrons compared to the ones generated by thermionic emission alone.
Anode
In the most basic form, an anode in electrochemistry is the point where an oxidation reaction occurs. Generally, at an anode, negative ions or anions due to its electrical potential tend to react and give off electrons. These electrons then move up and into the driving circuit.
If we take a galvanic cell, the anode is negative in nature and the electrons mostly move towards the external part of the circuit. In an electrolytic cell, it is again positive. Additionally, an anode can be a plate or wire having an excess positive charge.
Difference Between Anode And Cathode
Here are some key differences between cathode and anode.
Anode | Cathode |
The anode is the electrode where electricity moves into. | The cathode is the electrode where electricity is given out or flows out. |
The anode is usually the positive side. | A cathode is a negative side. |
It acts as an electron donor. | It acts as an electron acceptor. |
In an electrolytic cell, oxidation reaction takes place at the anode. | In an electrolytic cell, a reduction reaction takes place at the cathode. |
In galvanic cells, an anode can become a cathode. | In galvanic cells, a cathode can become an anode. |
