You should try with different working electrode and/or reference electrodes in order to check the best potential window of the blank solution. If you find abnormal peak you must change your solution or clean the electrode or bubble nitrogen inside the solution before putting in your sample.

Electrochemistry (especially cyclic voltammetry) is in general extremely sensitive towards contaminations of your electrolyte. If you see peaks in your CVs which do not belong there, then you have to clean your entire equipment thoroughly as Maddalena already suggested above. Otherwise your electrochemical data might be useless. Cleaning of the electrolytes by Ar or N2-bubbling is also required to remove dissolved oxygen from the solutions.

I would expect that the noble metals will have a quite large potential window, and then I expect silver as well as gold oxidation at anodic potentials, depending however on the pH of the solution. In anodic solutions, oxide layers wioll form for both Ag and Au, while in acidic (maybe also in neutral) phosphate buffer, Ag may corrode, while Au will be stable.

In any case it is required to play around with the potentials, scan speeds and reversal potentials in both anodic and cathodic direction.

Good luck, Dirk

Thank you very much for all sincere responses