Referenselektroden

Referenselektroden, or reference electrode, is an electrode with a stable and well-defined electrochemical potential used as a reference against which the potential of the working electrode is measured. Ideally, it carries little or no current. Its potential is set by a redox couple or hydrolysis in an electrolyte and should remain stable under the measurement conditions.

Common types include the saturated calomel electrode (SCE), which uses mercurous chloride in saturated potassium chloride and is stable at about 0.24 V vs the standard hydrogen electrode at 25°C. The silver/silver chloride electrode (AgCl/Ag) consists of a Ag/AgCl reference in a chloride solution and typically sits around 0.2 V vs SHE, depending on chloride concentration and temperature. Non-aqueous references exist for organic solvents, such as Ag+/Ag in acetonitrile or ferrocene/ferrocenium couples, and internal references are used in some systems. Some designs employ double-junctions to reduce junction potentials and contamination.

Key specifications are the potential stability and drift, junction potential with the test solution, chemical compatibility with the electrolyte, temperature dependence, and practicality of maintenance. The reference is connected to the potentiostat’s reference terminal, while the working and counter electrodes connect to the other terminals.

Reference electrodes are used in electroplating, corrosion testing, and analytical electrochemistry. The choice depends on solvent, pH, and desired potential range; aqueous systems commonly use AgCl in known chloride solutions or the SCE, while non-aqueous work may require alternative references.