Why is an external emf of more than $$2.2\ V$$ required for the extraction of $$Cl_{2}$$ from brine?
For the reaction:
$$2Cl^-(aq) + 2H_2O(l)\rightarrow 2OH^-(aq) + H_2(g) + Cl_2(g)$$,
the value of $$\Delta G^{\ominus}$$ is 422 kJ.
Using the equation $$\Delta G^{\ominus}=-nFE^{\ominus}$$ the value of $$E^{\ominus}$$ comes out to be -2.2 V.
Therefore extraction of $$Cl_2$$ from brine will require an external emf of greater than 2.2 V.