Electrolysis is a process that uses electricity to drive non-spontaneous chemical reactions. These chemical reactions break down a substance into simpler substances.
Electrolysis is performed using an electrolytic cell. To make an electrolytic cell, you need a power source, two electrodes, and an electrolyte solution. These are set up as shown in Figure 1. Each component has an important role to play, which is discussed below.
Figure 1 - A diagram showing how to set up an electrolytic cell.
The power source
The power source is the source of electrons, and these electrons drive electrolysis. The power source gives electrons to one electrode, called the cathode, and draws electrons from another electrode, called the anode. In an electrolytic cell, the cathode is negatively charged, and the anode is positively charged. These electrodes are placed in the electrolyte solution.
The purpose of the electrolyte is to carry charge between the electrodes. The electrolyte is a substance that can carry charge when molten or dissolved in solution. Often the electrolyte is a salt, but it can also be an acid, a base, or water. When in the liquid state, the electrolyte exists as positive ions called cations, and negative ions called anions.
To carry an electrical charge, the electrolyte must be in a liquid state. This is because in the liquid state the ions are free to move. The free movement of the ions means the ions can move to the oppositely charged electrode. The positive cations are attracted to the negative cathode, and the negative anions are attracted to the positive anode.
The main purpose of the electrodes is to pass charge between the power source and the electrolyte via chemical reactions. The electrodes can also be a source of ions in some applications such as electroplating.
As discussed above, the electrolyte contains ions, and the power source provides electrons to the electrodes. When the ions are at the electrodes, they take part in chemical reactions called redox reactions, where the ions exchange electrons with the electrodes. These reactions allow electrical charge to be passed between the cathode and anode.