Why is an external emf of more than 2.2V required for the extraction of Cl2 from brine?

Reaction involved in the extraction of Cl₂ from brine:

2Cl^– (aq) + 2H₂O(l) → 2OH^– (aq) + H₂(g) + Cl₂(g)

Calculation:

ΔGᶱ = -nFE°

ΔGᶱ = +422kJmol-1.

E° = 422×103 / 2×96500

E° = – 2.2V

For the reaction to take place the

Thus, the external voltage must be greater than 2.2V for the given extraction reaction to occur.