Studies on Ce4+ /Ce3+ redox system using linear polarization and ac impedance techniques

The electrochemical behavior of Ce4+/Ce3+ couple with various Ce4+ concentrations in a novel Ce4+/Ce3+-V2+/V3+ redox cell was investigated by linear polarization and ac impedance techniques. The results showed that Ce4+ concentration of 0.2 mol/L seemed to be the optimum concentration, at which the polarization resistance was minimized. But as the Coulomb and energy efficiency was considered in a work cell, the Ce4+ concentration should be selected as high as possible. When the Ce(SO4)(2) system was in a steady state, whether the sweep rate or the disturbance frequency was low, the reaction of Ce4+ was controlled by mass transfer. On the contrary, when the system was in a transient state, whether high sweep rate or high disturbance frequency was used, the reaction was controlled by charge transfer. While if the system was in a state between steady and transient, the whole reaction was controlled by the combination of charge transfer and mass transfer. Therefore, it would be considerably effective for the improvement of Ce4+/Ce3+ reaction to facilitate mass transfer and add electrochemical catalyst.