Question

why discharge potential of Cl is lower than OH

Answer 1

The two ions that u have asked are actually anions. These will get oxidized at anode during electrolysis.

Here the discharge potential in this case is actually the oxidation potential. The ion having greater oxidation potential will get discharged earlier at the anode.

Taking in view the Standard Oxidation Electrode potential of the ions, it is clearly inferred that OH- have relatively greater oxidation potential than Cl-

Therefore, Cl- have less discharge potential than OH-

Let me also clarify the hypertalked Electrolysis of NaCl. Here, H+ having greater reduction potential is discharged at cathode not Na+. At Anode OH- should be discharged not Cl-. But due to ‘overpotential’ Cl- is oxidized to Cl2 not OH-