hydrogen gas electrode

A thin foil of platinum electrolytically coated with a finely divided deposit of platinum or palladium metal, which catalyses the electrode reaction:
H + + e → 1 2 H 2
in solutions saturated with hydrogen gas.
PAC, 1985, 57, 531 (Definition of pH scales, standard reference values, measurement of pH and related terminology (Recommendations 1984)) on page 540