Usability of metals with different composition as cathode for electrochemical reduction of ferricyanide ion

In this study, the usability of metal alloys in 8 different compositions as electrodes in the potassium ferri-ferrous cyanide aqueous solution supported with an inert electrolyte (potassium carbonate), which is the most widely used system in electrochemical limiting current method, was investigated with the rotating disc electrode technique. In the experiments, it was observed that all metals provided a limiting current plateau, but not all gave a wide and uniform plateau, except one with almost pure Ni. As the Ni ratio of the metal increased, a smoother and wider plateau was obtained, and with a electrode containing 99% Ni, a very smooth and wide current plateau was obtained. In the second stage of the study, mass transfer to a circular local electrode with a diameter of 2 mm in a vessel container equipped with a six-blade turbine agitator was investigated using Ni electrode and potassium carbonate-supported-potassium ferri-ferro cyanide electrolyte system. The effects of the stirrer rotation speed (200-2000 rpm), Schmidt number (1500-60000) and the distance of the blade tip (x/dK = 0.022-0.222) to the local electrode on the mass transfer coefficients were examined. The electrolytic solutions containing 0-50% glycerin was used to obtain a wide range of Schmidt numbers. It was observed that increasing rotating speed and decreasing turbine blade tip to electrode distance and decreasing Schmidt number increased the mass transfer rate. With the decrease in the distance between the turbine blade and the disc electrode, an increase in mass transfer between 2.6% and 19.0% was achieved depending upon Schmidt number. As a result of the statistical analysis, it was found that all the experimental data would be well correlated with the equation Sh=8.517*(Re^0.473)*(Sc^0.402)*((x/d_K)^−0.042).