05917 IUPAC Gold Book - standard hydrogen electrode 10.1351/goldbook.S05917 S05917 current 1 For solutions in protic solvents, the universal reference electrode for which, under standard conditions, the standard electrode potential ($\ce{H^{+}}$/$\ce{H2}$) 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: \[E^{\,\unicode{x26ac}}\left(\rm{H}^{+}/\rm{H}_{2}\right)\left(\rm{abs}\right)=\Delta _{\rm{at}}G^{\,\unicode{x26ac}}+\Delta _{\rm{ion}}G^{\,\unicode{x26ac}}+\frac{\alpha _{\rm{H}^{+}}^{\rm{o,S}}}{F}\] where \(\Delta _{\rm{at}}G^{\,\unicode{x26ac}}\) and \(\Delta _{\rm{ion}}G^{\,\unicode{x26ac}}\) are the atomization and ionization Gibbs energies of $\ce{H2}$, \(\alpha _{\rm{H}^{+}}^{\rm{o,S}}\) is the real potential of $\ce{H2}$ in solvent $\ce{S}$ and \(F\) is the Faraday constant. The recommended absolute electrode potential of the hydrogen electrode is: \[E^{\,\unicode{x26ac}}\left(\rm{H}^{+}/\rm{H}_{2}\right)^{\rm{H}_{2}\rm{O}}\left(\rm{abs}\right)=(4.44\pm 0.02)\ \rm{V}\quad \rm{at}\quad 298.15\ \rm{K}\] Faraday constant https://goldbook.iupac.org//terms/view/F02325 absolute electrode potential https://goldbook.iupac.org//terms/view/A00022 ionization https://goldbook.iupac.org//terms/view/I03183 protic https://goldbook.iupac.org//terms/view/P04900 reference electrode https://goldbook.iupac.org//terms/view/R05229 standard electrode potential https://goldbook.iupac.org//terms/view/S05912 PAC, 1986, 58, 955. 'The absolute electrode potential: an explanatory note (Recommendations 1986)' on page 957 (https://doi.org/10.1351/pac198658070955) https://goldbook.iupac.org/terms/view/S05917/html https://goldbook.iupac.org/terms/view/S05917/json https://goldbook.iupac.org/terms/view/S05917/plain Citation: 'standard hydrogen electrode' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.S05917 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-04-21T20:47:59+00:00