According to convention, a half-cell
called standard hydrogen electrode (Fig 3 3)
represented by Pt(s)ú H2(g)ú H+(aq), is assigned
a zero potential at all temperatures
corresponding to the reaction
    H+ (aq) + e–  ®  1
2 H2(g)
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