An electrode used as a reference for measuring electrode potential. Strictly speaking, the standard hydrogen electrode is an ideal electrode, which is not actually realized. Therefore, in the actual measurement of electrode potential, the electrode with the electrode potential accurately known and very stable is always used as the comparison electrode. By measuring the electromotive force of the battery composed of this kind of electrode and the measured electrode, the electrode potential of the measured electrode can be calculated.
The electrode reaction on the reference electrode must be a single reversible reaction with high exchange current density, easy fabrication, good reproducibility and stable electrode potential. Generally, refractory salt electrode is used as the reference electrode. The reference electrode should not be easily polarized; If the current is too large to produce polarization, the electrode potential should be able to recover the original value soon after the power is cut off; The change of electrode potential hysteresis should be small when the temperature changes.