My CV profile shows redox peaks at around -0.3V in the potential window -0.7 to 0.3V. But in GCD, the discharge curve is not going below -0.25V. If the potential window of GCD is followed i.e. -0.25 to 0.3V then I don't see any redox peaks in the CV curve? Can someone explain please.
Dinesh Kshetrimayum You might try to minimize the possible window to prevent the OER and reduce the CV scan rate to address this problem.
Good question! The likely explanation here is that the redox reactions occurring in your system have some kinetic limitations that impact the galvanostatic charge-discharge (GCD) measurements but not the cyclic voltammetry (CV).
In CV, you are dynamically and continuously scanning the potential to drive oxidation and reduction processes. So even slower kinetic reactions have time to occur at their thermodynamic potentials.
However in GCD, the potential response comes from the system naturally as it tries to deliver the fixed current/flux that you apply. If the kinetics are sluggish, the potential may hit limits before fully accessing those redox processes.
So in your case, when discharging galvanostatically, the kinetics likely limit the reduction reaction, preventing the potential from going below -0.25V vs your reference. But in the CV, you drive the potential low enough with your dynamic scanning to see that reduction peak at -0.3V.
This type of mismatch can give insights into reaction limitations. You can also try altering scan rates in CV or current densities in GCD to further study the kinetics.
Thank you @ Alvena Shahid and Ahmed Emad for your insights.
Regards