The measurement of the diffusion coefficients of ferrocene and ferrocenium and their temperature dependence in acetonitrile using double potential step microdisk electrode chronoamperometry

The diffusion coefficients of both ferrocene (Fc) and ferrocenium (Fc(+)) in acetonitrile containing 0.1 M tetra-n-butylammoniumperchlorate (TBAP) or 0.1 M tetra-n-butylammoniumhexafluorophosphate (TBAPF(6)) are reported, determined using the technique of double potential step chronoamperometry at a microdisk electrode. Activation energies of diffusion, E-a,E-D are calculated for both redox species in each system. Diffusion coefficient ratios of the diffusion coefficients of Fc compared to that of Fe in each case were found to be very close to 1. Activation energies of diffusion, E-a,E-D for ferrocene and ferrocenium in the acetonitrile/perchlorate system were determined as 6.5 (+/- 0.2) and 7.2 (+/- 0.5) kJ mol(-1), respectively. Similar values were determined for the acetonitrile/hexafluorophosphate system: 7.1 (+/- 0.1) kJ mol(-1) for Fc and 7.4 (+/- 0.3) kJ mol(-1) for Fc(+). Cyclic voltammograms were recorded for ferrocene oxidation in both acetonitrile/electrolyte systems and it was observed that the E-1/2 values were similar and independent of the electrolyte used. (C) 2010 Elsevier B.V. All rights reserved.