How It Works: Ion Migration in Molten Electrolysis

⚙️ How It Works: Ion Migration in Molten Electrolysis

In a molten ionic compound, the ionic lattice has broken down due to the high temperature. This means the positive metal ions (cations) and negative non-metal ions (anions) are no longer fixed in position — they can move freely through the liquid.

When a direct current (DC) is applied, the cations experience an electrostatic attraction towards the negative cathode. They migrate through the liquid electrolyte and arrive at the cathode surface. Here, each cation picks up electrons directly from the electrode — this electron transfer is called reduction. The metal ions become neutral atoms and are deposited as solid or liquid metal at the cathode.

Simultaneously, the anions are attracted to the positive anode. When they arrive, each anion gives up its extra electrons to the electrode — this is oxidation. The neutral atoms (or pairs of atoms) form at the anode as molecules. For example, bromide ions pair up to form bromine molecules (Br₂).

Note that electrons do NOT travel through the electrolyte — they travel through the external circuit from anode to power supply to cathode. Inside the electrolyte, it is the movement of ions that carries the current. This is a key distinction: in metals, electrons carry current; in electrolytes, ions carry current.