Hi Dear Archana, The absence of the oxidation peak at higher scan rates (80-100 mV/sec) during CV on the modified electrode could be due to several reasons. Firstly, mass transport limitations may hinder the diffusion of the electroactive species to the electrode surface within the shortened time intervals, resulting in a reduced or absent oxidation peak. Additionally, adsorption effects could prevent the participation of the electroactive species in the oxidation process, particularly if desorption is challenging at higher scan rates. Slower electrode kinetics or complex reaction mechanisms at high scan rates may also contribute to the absence of the oxidation peak. Moreover, the prominence of capacitive currents associated with the double-layer charging at high scan rates can overshadow the oxidation peak. It is important to consider other experimental factors such as the choice of electrolyte, pH, temperature, electrode material, and surface modifications, as they can also influence the absence of the oxidation peak. Further analysis and consultation with experts in the field may help to better understand the specific reasons for the observed results.

Thank you, Tayyaba Iftikhar, for this detailed answer. Can you please provide a valid reference for it too? Would be a great help.

Yes, Please read the attached articles; Article Influence of scan rate on CV Pattern: Electrical and electro...

Article Hydrogen Oxidation Artifact During Platinum Oxide Reduction ...

This is due to the charging current coming from double layer charging. To find optimum scanning rate, apply the Randles-Sevcik equation and plot ip vs root of scanning rate, you will get straight line. At higher scanning rate, the peak current deviates from the line. Better to use lower scanning rate to avoid much charging current.