Activity of Nafion
From the data obtained at the Nafion modified electrodes, ip (ip is peak current) varies with inert electrolyte cation. For plots of ip versus v1/2 (v is scan rate), inert electrolytes with the same cation had similar slopes where the observed peak currents ranked as H+ > Na+ > K+. Cations with smaller hydration energies are more easily exchanged into Nafion. The redox probe had no voltammetric response with high concentrations of the smaller cation electrolytes, consistent with little probe in the film. However, even for small cation electrolytes, at sufficiently low electrolyte concentrations, Ru(bpy)32+ yields a voltammetric response. From the slopes of ip versus v1/2, Cfilm Dfilm1/2 is found, where Cfilm and Dfilm are the concentration and the diffusion coefficient of Ru(bpy)32+ in the film. Cfilm Dfilm1/2 does not change with the electrolyte concentration. Convolution will further refine determination of Cfilm Dfilm1/2 and the dielectric constant will allow further evaluation of activity effects in Nafion.