Inertness: Mercury is a relatively inert metal that does not easily undergo oxidation or reduction reactions. This makes it suitable for use as an electrode material that does not interfere with the electrode reactions of interest.
High hydrogen overpotential: Mercury has a high overpotential for hydrogen evolution, meaning that a relatively large potential is required to generate hydrogen gas on a mercury surface. This property ensures that the SHE operates at a well-defined and reproducible potential.
Good electrical contact: Mercury forms a good electrical contact with the platinum wire that serves as the current collector in the SHE. This ensures efficient transfer of electrons between the electrode and the external circuit.
Absence of oxide layer: Unlike many other metals, mercury does not form a stable oxide layer on its surface. This eliminates the issue of surface passivation, which can affect the electrode's stability and reproducibility.
Convenient to use: Mercury is liquid at room temperature, making it easy to handle and shape into a suitable electrode configuration. It can be easily renewed by simply shaking the electrode, which exposes a fresh mercury surface.
The combination of these properties makes mercury an ideal choice for use in the standard hydrogen electrode, ensuring its reliability, accuracy, and reproducibility as a reference electrode in electrochemical measurements.
