Polymer films on electrodes. 9. Electron and mass transfer in Nafion films containing tris(2,2'-bipyridine)ruthenium(2+)

The electrochemical behavior of Ru(bpy),2+ (bpy = 2,2'-bipyridine) contained in 2-"thick films of the perfluorosulfonate polymer Nafion on glassy carbon is described. The apparent diffusion coefficient, D, , for the 2+ and 3+ forms was determined by potential-step chronoamperometric measurements to be (5 & 2) X cm*s-l. Dapp for the 2+ form was independent of loading of R ~ ( b p y ) , ~ + in the film. The shapes of the cyclic voltammetric (current-potential) waves for the system were fit by digital simulation techniques with a model involving interactions between the electroactive groups as well as interconversions of different forms of the 2+ and 3+ species. Recent reports from this labora t~ry l -~ have described polymer electrodes based on the ion-containing polymer Nafion.4 Because (CF2 C Fz )I (C FC F21? I O-GF~) G C F ~ C F ~ SGCN: