First, the effect of the reactant valence on CV shape was investigated by simulation on conditions of no supporting electrolyte (𝐶 sup = 0 ) . Simulated CVs and migration potential difference Δ𝜙 at 𝑧 A = -3, -1, 1, and 3 are shown in Fig. , where Δ𝜙 = 𝜙 PET -𝜙 bulk : potential difference between the plane of electron transfer (PET) and the solution bulk. It is important to note that the definition of PET is the point at the edge of the electrical double layer. Therefore, Δ𝜙 is not the potential difference between the electrode and the reaction surface, and Δ𝜙 is usually treated as zero in systems where migration can be ignored.