Non-Steady-State Rotating Disk Voltammetry of Redox Couples Incorporated in Perfluorsulfonated Ionomer Coatings on Electrodes

The differences in the affinity of Nafion coatings for Ru(NH_3)_6^(3+/2+) and Os(bpy)_3^(3+/2+) counterions and the difference in the mobilities of the two types of cations within Nafion are used to explain the differences in the voltammetric signatures that they exhibit. A new method is proposed with which to determine whether apparent diffusion coefficients of electroactive counterions in electrode coatings differ when they are evaluated in transient or in steady-state experiments. The utility of non-steady-state cyclic voltammetry with Nafion-coated rotating disk electrodes to separate the contribution to the observed current from dissolved and Nafion-confined reactants is demonstrated.