standard hydrogen electrode

For solutions in protic solvents, the universal reference electrode for which, under standard conditions, the standard electrode potential (H⁺ / H₂) is zero at all temperatures. The absolute electrode potential of the hydrogen electrode under standard conditions can be expressed in terms of thermodynamic quantities by applying a suitable Born–Haber cycle, thus:

$E ° H + / H 2 abs = Δ at G ° + Δ ion G ° + α H + o,S F$

where $Δ at G °$ and $Δ ion G °$ are the atomization and ionization Gibbs energies of H₂, $α H + o,S$ is the real potential of H₂ in solvent S and $F$ is the Faraday constant. The recommended absolute electrode potential of the hydrogen electrode is:

$E ° H + / H 2 H 2 O abs = ( 4.44 ± 0.02 ) V at 298.15 K$

Source:

PAC, 1986, 58, 955 (The absolute electrode potential: an explanatory note (Recommendations 1986)) on page 957