Demonstration of Superiority of the Marcus-Hush Electrode Kinetic Model in the Electrochemistry of Dissolved Decamethylferrocene at a Gold Modified Electrode by Fourier Transformed Alternating Current Voltammetry

Fourier-transformed alternating current (AC) voltammetry is used to compare the applicability of the Butler-Volmer (BV) and Marcus-Hush (MH) models of electrode kinetics (k⁰) to an outer-sphere electrode process where both oxidized and reduced species are soluble. According to numerical simulations, differences between the two models can be revealed clearly by analysis of the AC harmonics when the values of k⁰ and reorganization energy are sufficiently small. Experimentally a Au electrode coated with a self-assembled octanethiol monolayer was introduced to decrease the rate of the DmFc^0/+ (DmFc = decamethylferrocene) process, a well-known outer-sphere process in a propylene carbonate solution containing 0.10 M tetrapropylammonium tetrafluoroborate. Based on a comparison of the computationally generated best fits, it was demonstrated that the MH model provides substantially better agreement with the experimental data than the BV model for the DmFc^0/+ process, unlike some other examples in the literature that favor the BV model.