Cathodes and anodes are electrodes. These are carbon or metal rods that are connected to an electric current. When they are placed in an electrolyte, current can pass through the liquid from one electrode to the other, so completing the circuit. The cathode has a negative electrical charge and the anode has a positive electrical charge. Ions in the electrolyte are being held together because they have opposite electrical charges, which attract each other. These bonds are broken because the ions with positive charges are more strongly attracted to the negative charge of the cathode than they are to the negative charge of the ions with which they are bonded. In the same way, negatively charged ions are attracted to the anode.
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 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.
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