What happens at the cathode during electrolysis?

During electrolysis, the cathode attracts cations where reduction reactions occur.

In more detail, electrolysis is a process that uses an electric current to drive a non-spontaneous chemical reaction. This process takes place in an electrolytic cell, which is composed of two electrodes: an anode and a cathode. The cathode is the electrode where reduction occurs, meaning it is the site where cations (positively charged ions) are attracted to.

Cations are attracted to the cathode because it is negatively charged. Once they reach the cathode, they gain electrons and are reduced. This reduction process can be summarised by the general equation: Cation + electron(s) → Neutral atom. For example, if copper ions (Cu2+) are present in the electrolyte, they will be attracted to the cathode, gain two electrons and be reduced to copper atoms (Cu).

The specific reactions that occur at the cathode can vary depending on the electrolyte used and the materials of the electrodes. For instance, if the electrolyte is a solution of sodium chloride (NaCl), the cations present are sodium ions (Na+) and hydrogen ions (H+). If the cathode is inert, such as platinum or graphite, the hydrogen ions are preferentially reduced, producing hydrogen gas. However, if the cathode is made of a more reactive metal, such as iron, the sodium ions may be reduced instead.

In summary, the cathode plays a crucial role in electrolysis as the site of reduction reactions. It attracts cations from the electrolyte, which then gain electrons and are reduced to their neutral form. The specific reactions that occur can vary, but the fundamental process of reduction remains the same.