AgAgClElektrode

AgAgClelektrode, commonly called the Ag/AgCl electrode, is a widely used reference electrode in electrochemistry. It consists of a silver metal element that is coated with a thin layer of silver chloride and immersed in a chloride-containing electrolyte. The electrode establishes a stable, well-defined potential through the redox couple AgCl(s) + e− ⇌ Ag(s) + Cl−. In practice, its potential is set by the activity of chloride ions in the surrounding solution and by the fill solution used inside the electrode, typically saturated or concentrated potassium chloride (KCl).

Construction and design variations

A typical AgAgClelektrode uses a silver wire or rod coated with AgCl, housed in a glass or polymer casing with a small internal chamber filled with a chloride-rich electrolyte. The tip is separated from the measurement solution by a porous frit or salt bridge, allowing ionic contact while limiting bulk mixing. Common fill solutions are saturated KCl or 3 M KCl, chosen to provide a stable Cl− activity and minimize potential drift. The electrode is connected to the rest of the electrochemical cell via a conducting lead.

Operating principles and performance

The electrode potential is governed by the chloride concentration through the Nernst equation, making the Ag/AgCl potential sensitive to changes in Cl− activity. It offers relatively low drift, good stability, and inexpensive fabrication, which makes it a preferred reference in many aqueous electrochemical measurements, including voltammetry and corrosion studies. Performance can be affected by drying of the fill solution, exposure to non-chloride media, or contamination that alters the AgCl layer.

Applications and considerations

Ag/AgCl electrodes are favored for their stability and compatibility with chloride-containing solutions. They are less suited to strongly oxidizing environments or non-aqueous media unless specially adapted. Regular maintenance involves ensuring a moist fill solution, minimizing leaks, and replacing worn AgCl coatings to preserve a stable reference potential.