HYDROGEN ELECTRODE

"A redox electrode with dissolved hydrogen gas being the reduced species and hydrogen ions the oxidized species. Hydrogen gas (or a gas mixture containing hydrogen) is bubbled through the electrolyte to keep a desired dissolved hydrogen content. The inert metallic electrode is usually platinized platinum. The equilibrium potential of this electrode depends on the concentration (strictly speaking, activity) of both the hydrogen ions and the dissolved hydrogen gas (controlled by the hydrogen gas pressure), see Nernst equation. The electrode can be used as a measuring electrode in a sensor to determine the hydrogen ion concentration (pH), or it can be used as a reference electrode if all the concentrations are known and constant. It is used equally often for both purposes. It is also the most fundamental reference electrode as the standard hydrogen electrode. See also the dynamic hydrogen electrode and the reversible hydrogen electrode. "