Temperature dependence of kinetics and diffusion coefficients for ferrocene/ferricenium in ammonium-imide ionic liquids

The electrochemical behavior of ferrocene (Fc) and ferricenium (Fc+) was investigated by cyclic voltammetry with convolutional and semi-differential electroanalyses in the temperature range 298–373 K in the hydrophobic room temperature ionic liquid systems consisting of bis(trifluoromethanesulfone)imide anion with quaternary ammonium cation. The experimental results indicated that the redox reaction of Fc/Fc+ was reversible in this ionic liquid and the charge-transfer rate constant (k0) has been obtained. Mass transport towards the electrode is a simple diffusion process and the diffusion coefficient (D) for Fc/Fc+ has been also calculated. These results indicated that the k0 and D increased with increasing temperature in ionic liquids. The validity of the Arrhenius law was verified by investigating the temperature dependences of k0 and D.