KINETIC STUDY OF THE FERROCENE COMPLEX IN BINARY IONIC LIQUID MEDIA

Abstract

A binary ionic liquid (ILs)-based electrolyte with advanced physicochemical properties has been successfully prepared. The ionic conductivity ( σ ) values of ILs [C 4 mim][PF 6 ] and [C 4 mim][Tf 2 N] were measured using electrochemical impedance spectroscopy are 2.12 and 4.75 mS/cm at 30  C, respectively. The results of electrode kinetics measurement using cyclic voltammetry revealed a value of the diffusion coefficient ( D ) of ferrocene in [C 4 mim][PF 6 ] of 3.3 x 10 -7 cm 2 /s and [C 4 mim][Tf 2 N] 1.60 x 10 -6 cm 2 /s. The ferrocene complex obtained has an electron transfer rate constant ( k s ) of 7.9 x 10 -4 cm/s in [C 4 mim][PF 6 ] and 1.82 x 10 -3 cm/s in [C 4 mim][Tf 2 N]. The addition of [C 4 mim][Tf 2 N] to [C 4 mim][PF 6 ] increased ionic conductivity, diffusion coefficient, and electron transfer rate constant overall, but only to the range of pure ILs. Furthermore, changes in conductivity, diffusion coefficient, and electron transfer rate constant value are proportional to temperature changes, according to the Arrhenius equation. Based on the diffusion activation energy ( E a D ) and the slight decrease in conductivity with temperature, [C 4 mim][PF 6 ] 0.50 -[C 4 mim][Tf 2 N] 0.50 is a superior electrolyte candidate at low-temperature operation.