Mediated Electron Transfer at Redox Active Monolayers. Part 3: Bimolecular Outer-Sphere, First Order Koutecky-Levich and Adduct Formation Mechanisms

A number of theoretical models describing the transport and kinetic processes involved in heterogeneous redox catalysis of solution phase reactants at electrode surfaces coated with redox active monolayers (such as self assembled alkane thiols containing a ferrocene group) is presented. These models are : simple bimolecular outer-sphere, generalized Koutecky-Levich, and substrate binding/ adduct formation . For each model a general expression for the steady state reaction flux is derived. Simplified analytical expressions for the net reaction flux under steady state conditions, are derived for experimentally reasonable situations, and kinetic case diagrams are constructed outlining the relationships between the various approximate solutions. The theory developed enables simple diagnostic plots to be constructed which can be used to analyse experimental data.