As shown in Fig. , the negative Δ𝜙 value increases as the reduction current increases at negative potentials. This would be due to a greater breaking of the electroneutrality in the vicinity of the electrode surface as the reduction current increased. As described above, the |Δ𝜙| value for the formal potential of rate determining step (rds), 𝛼: the transfer coefficient, 𝑘 0 : the standard rate constant, 𝐷: the diffusion coefficient. 𝒯: the absolute temperature, 𝜀 s : the relative permittivity of the solvent).