Reaction at Electrode:
The electrode is now suitably strong reductant to reduce [FeIII(CN)6]3- to FeII(CN)6]4- The cathodic current increases rapidly (b → d) until the concentration of [FeIII(CN)6]3- at the electrode surface is substantially diminished, resulting the current to peak (d). The current then decays ( d → g) as the solution surrounding the electrode is depleted of [FeIII(CN)6]3- due to electrolytic conversion to [FeII(CN)6]4- . The scan direction is then switched to positive at -0.15 V (t) for the reverse scan. A potential is still sufficiently negative to reduce [FeIII(CN)6]3- , so the cathodic current continues even though the potential is now scanning in the positive direction. When the electrode becomes sufficiently strong oxidant, [FeII(CN)6]4-, that has been accumulating adjacent to the working electrode, could now be oxidized through the electrode process:
[FeII(CN)6]4- → [FeIII(CN)6]3- + e