The presence of a loop (reverse or crossed return) in cyclic voltammetry is due to the fact that the reaction which took place at the electrode leads to the electrodeposition of a polymer or of a species strongly adsorbed on the electrode during the forward scan of the voltammogram, and the latter detaches or becomes desorbed during the back scan of the voltammogram. This often occurs during the electropolymerization of electroactive monomers into conductive organic polymers. It is particularly observed when drawing the first cycle of the voltamogram. In your case, it's probably phosphonates that adsorb on the electrode.

The presence of a loop (reverse or crossed return) in cyclic voltammetry is due to the fact that the reaction which took place at the electrode leads to the electrodeposition of a polymer or of a species strongly adsorbed on the electrode during the forward scan of the voltammogram, and the latter detaches or becomes desorbed during the back scan of the voltammogram. This often occurs during the electropolymerization of electroactive monomers into conductive organic polymers. It is particularly observed when drawing the first cycle of the voltamogram. In your case, it's probably phosphonates that adsorb on the electrode.

@Belkacem,

Thank you for your answer and clear explanation. I understand the concept from your answer.

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https://www.researchgate.net/post/Is_there_any_literature_about_using_the_combination_of_material_such_as_Au-Pt_alloy_for_counter_electrode_in_cyclic_voltammetry