Why is an external emf of more than 2.2V required for the extraction of ${\mathrm{Cl}}_{2}$from brine?

For the given reaction, value of $∆$G° is + 422 kJ,
Using $∆$G° = - nFE°, the value of E° =-2.2V,
Therefore, an external emf greater than 2.2 V is required for the extraction of ${\mathrm{Cl}}_{2}$ from brine.