Influence of 1-butyl-3-methylimidazolium on the electron transfer kinetics associated with the [SVW11O40]3 −/4 − (VV/IV) and [SVW11O40]4 −/5 − (WVI/V) processes in dimethylformamide

Abstract

Fourier transformed large amplitude alternating current voltammetry has been used to determine the heterogeneous electron-transfer kinetics (k0 and α values) associated with the vanadium [SVW11O40]3−/4− (VV/IV) and tungsten [SVW11O40]4−/5− (WVI/V) processes at glassy carbon (GC), platinum (Pt), gold (Au) and boron-doped diamond (BDD) electrodes in dimethylformamide (DMF) containing 0.5M 1-butyl-3-methylimidazolium hexafluorophosphate as the supporting electrolyte. In comparison with data reported previously in DMF containing 0.5M tetrabutylammonium hexafluorophosphate, the k0 values at Pt, Au and BDD electrodes, were found to be larger by a factor of 2 to 4 for the VV/IV process and 10 to 100 fold for the WVI/V process. At a GC electrode, the rate of the VV/IV process was too fast to be measured under the experimental conditions used (frequency=34Hz) and k0 for the WVI/V process was found to be insensitive to the identity of the supporting electrolyte cation. The origins of these observations are considered in terms of contributions from ion-pairing, surface functional groups on the GC electrode, the double layer effect, and the inner-sphere nature of the WV/IV process.