Molecular insights into electron transfer processes via variable temperature cyclic voltammetry. Application of the asymmetric Marcus-Hush model

The study of the variation of the kinetics of electrode processes with temperature is performed considering the asymmetric version of the Marcus theory for the first time. This kinetic model introduces a new symmetry parameter that takes into account possible differences between the inner-sphere force constants of the oxidized and reduced electroactive species. Variable temperature measurements in fast-scan cyclic voltammetry are employed to gain further insights into the molecular properties of the electroreduction of 1-nitropentane in acetonitrile on mercury hemispherical microelectrodes of 28.5 μm radius. Thus, the values of the reorganization energy of the electron transfer process and the symmetry parameter as well as the degree of adiabaticity of the electron transfer reaction are evaluated. The results are also analyzed in terms of the ability of the different kinetic models employed in Electrochemistry (Butler-Volmer, symmetric Marcus-Hush and asymmetric Marcus-Hush) to fit the experimental voltammograms with consistent values for the kinetic parameters in a range of temperatures and scan rates.