Electrochemical Behavior of Potassium Ferricyanide in Aqueous and (w/o) Microemulsion Systems in the Presence of Dispersed Nickel Nanoparticles

Abstract

The electrochemical behavior of the redox couple ferro/ferricyanide has been investigated in aqueous 1.0 M KNO3 and in (w/o) microemulsion using cyclic voltammetry (CV) and chronoamperometry (CA). The (w/o) microemulsion was composed of the non-ionic surfactant Tween-80, tetrabutylammonium perchlorate (TBAP) supporting electrolyte, HepTol, and dichloromethane as the continuous phase and the aqueous probe solution. In the aqueous supporting electrolyte solution of 1.0 M KNO3, the redox pair showed a reversible electrochemical behavior and followed Randles-Sevcik and Cottrell equations, however, with concentration-dependent diffusion coefficients. In the (w/o) microemulsion system, on the other hand, the probe showed an irreversible behavior mainly due to the adsorption of surfactant onto the working electrode, which hindered the charge transfer step. The presence of dispersed Ni nanoparticles in the aqueous solution did not have an effect on the electrochemical behavior of the redox couple, while it enhanced the reduction decay current in the (w/o) microemulsions. This observation was attributed to a more rapid charge transfer in a medium with inherently very low conductivity.