Dear Hamada

Thank you very much for your answer. I read all of the above suggested paper. Unfortunately, none of the paper explains about the potential sweeping in ORR. If you can suggest me the general procedure for performing ORR, i.e. forward scan or reverse scan?

Oxygen Chemistry (International Series of Monographs on Chemistry) 1st Edition

by Donald T. Sawyer (Author),‎ R. J. P. Williams (Foreword)

Oxford University Press; 1 edition (September 19, 1991)

the proper method for doing ORR is start from less negative potential to more negative potential.take linear sweep voltametry and take the one cycle

Thank you for your answer. But reverse scan (more negative potential to less negative potential) gives better half wave potential value. Why can not we consider the reverse scan result? If you can refer me some references it will be very helpful.

In the anodic (reverse, as described by you) scan, the process is an oxidation. For reduction, your first choice must be a cathodic (direct, as described by you) scan.

Thank you very much Cornel Sir for your answer. Hence, for all reduction reactions cathodic scan should be performed.

We study ORR from 0.2 to -1.0 V (Ag/AgCl sat) for stabilization in N2 (30 cycles, 50 mVs-1), then from -1.0 to 0.2 V for O2 ORR kinetics in RDE (1 cycle, 5 mVs-1).