24.2.2—Standard hydrogen electrode

The standard hydrogen electrode uses a platinum surface, H₂ gas at standard pressure, H⁺ solution at standard concentration and a specified temperature. Its reduction potential is defined as 0.00 V.

The platinum is an inert conductor and catalyst; it is not consumed. Connecting another half-cell to the SHE lets its E° be measured directly relative to the zero reference.

If a metal half-cell connected to the SHE gives E°cell=−0.76 V when the metal is the reduction side, its standard reduction potential is −0.76 V.

The SHE is not a container of hydrogen ions only; gas pressure, concentration, temperature and the platinum electrode are part of the standard setup.