Why do some electrochemical cells employ inert electrodes such as platinum?

An electrochemical cell is a device that can generate electrical energy from chemical reactions or facilitate chemical reactions through the introduction of electrical energy. At the heart of these cells are two types of reactions: oxidation, which occurs at the anode, and reduction, which takes place at the cathode. During oxidation, electrons are lost, while reduction involves the gain of electrons.

When a substance loses electrons at the anode, it generates a positive charge, with the lost electrons traveling through an external circuit towards the cathode where another substance gains them, signifying reduction. The flow of electrons from anode to cathode through the circuit is what we harness as electrical energy. It's important to note that without the completion of this circuit — including the return path for ions in the electrolyte solution — the electrochemical cell cannot function.

Electrodes play a crucial role in both galvanic (voltaic) and electrolytic cells, as they provide the physical site at which oxidation and reduction reactions occur. There are typically two electrodes in any electrochemical cell: the anode, where oxidation occurs, and the cathode, where reduction happens. These reactions are fundamental to the cell's ability to produce or consume electricity.

To facilitate these reactions, electrodes need to conduct electricity efficiently. The nature of the material composing the electrodes can greatly affect the cell's overall efficiency and the specificity of the reactions. For instance, reactive electrodes might introduce additional and undesired chemical reactions, whereas inert electrodes avoid these complications.

Inert electrodes such as platinum or graphite are preferred in many electrochemical cells due to their non-reactive nature. The importance of inertness cannot be overstated; it ensures that the electrodes do not become involved in the cell's chemical reactions except to transfer electrons. This preserves the purity of the chemical processes occurring within the cell.

Using inert electrodes is particularly critical in cells where the electrode might otherwise react with the reactants or products, altering the intended reactions or potentially damaging the cell. For example, in a solution where chlorine gas is produced, a non-inert electrode might corrode, but platinum, being inert, would not.

Inert electrodes maintain the integrity and stability of the cell over time, which is essential for applications that require precise control over the chemical reactions, such as analytical measurements in laboratories, or industrial processes where product consistency is vital.