The standard hydrogen electrode consists of a platinum electrode coated with platinum black. The electrode is dipped in an acidic solution and pure hydrogen gas is bubbled through it.
The concentration of both the reduced and oxidised forms of hydrogen is maintained at unity. This implies that the pressure of hydrogen gas is one bar and the concentration of hydrogen ion in the solution is one molar.
Above half-cell called standard hydrogen electrode (Fig.) represented by Pt(s)| H2(g) |H+(aq), is assigned a zero potential at all temperatures corresponding to the reaction.
