Copper-copper(II) sulfate electrode

Diagram of an electrode used in the field

The Copper-copper(II) sulfate electrode is a reference electrode of the first kind, based on the redox reaction with participation of the metal (copper) and its salt - copper(II) sulfate. It is used for measuring electrochemical potential and is the most commonly used reference electrode for testing cathodic protection corrosion control systems.

The corresponding equation can be presented as follow:

Cu²⁺ + 2e^- → Cu⁰(metal)

This reaction characterized by reversible and fast electrode kinetics, meaning that a sufficiently high current can be passed through the electrode with the 100% efficiency of the redox reaction (dissolution of the metal or cathodic deposition of the copper-ions).

The Nernst equation below shows the dependence of the potential of the copper-copper(II) sulfate electrode on the activity or concentration copper-ions:

$E=0.337 + \frac{RT}{2F} ln a_{Cu^{2+}}$

Commercial reference electrodes consist of a plastic tube holding the copper rod and saturated solution of copper sulfate. A porous plug on one end allows contact with the copper sulfate electrolyte. The copper rod protrudes out of the tube. A voltmeter negative lead is connected to the copper rod.

The potential of a copper copper sulfate electrode is +0.314 volt with respect to the standard hydrogen electrode.(citation needed)

Applications

• Cathodic Protection
• Copper coulometer
• Copper-copper(II) sulfate electrode is also used as a one of the half cell in the Daniel-Jakobi galvanic cell.

References

• E. Protopopoff and P. Marcus, Potential Measurements with Reference Electrodes, Corrosion: Fundamentals,

Testing, and Protection, Vol 13A, ASM Handbook, ASM International, 2003, p 13-16

• A.W. Peabody, Peabody's Control of Pipeline Corrosion, 2nd Ed., 2001, NACE International. ISBN 1575900920