Reference electrode

A reference electrode is an electrode which has a stable and well-known electrode potential. The high stability of the electrode potential is usually reached by employing a redox system with constant (buffered or saturated) concentrations of each participant of the redox reaction.

There are many ways reference electrodes are used. The simplest is when the reference electrode is used as a half-cell to build an electrochemical cell. This allows the potential of the other half cell to be determined. An accurate and practical method to measure an electrode's potential in isolation (absolute electrode potential) has yet to be developed.

Nonaqueous reference electrodes

While it is convenient to compare between solvents to qualitatively compare systems, this is not quantitatively meaningful. Much as pKa are related between solvents, but not the same, so is the case with E°. While the SHE might seem to be a reasonable reference for nonaqueous work as it turns out the platinum is rapidly poisoned by many solvents including acetonitrilecausing uncontrolled drifts in potential

Aqueous reference electrodes

Common reference electrodes and potential with respect to the standard hydrogen electrode. Example

• Standard hydrogen electrode (SHE) (E=0.000 V) activity of H+=1 Molar
• Normal hydrogen electrode (NHE) (E ≈ 0.000 V) concentration H+=1 Molar

Pseudo reference electrodes

A pseudo reference electrode is a term that is not well defined and borders on having multiple meanings since pseudo and quasi are often used interchangeably. They are a class of electrodes named pseudo-reference electrodes because they do not maintain a constant potential but vary predictably with conditions. If the conditions are known, the potential can be calculated and the electrode can be used as a reference. Most electrodes work over a limited range of conditions, such as pH or temperature, outside of this range the electrodes behavior becomes unpredictable. The advantage of a pseudo-reference electrode is that the resulting variation is factored into the system allowing researchers to accurately study systems over a wide range of conditions.

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Journal of Analytical Electrochemistry