AN ULTRAMICROELECTRODE STUDY OF FERROCENE DIFFUSION AND HETEROGENEOUSELECTRON-TRANSFER RATE IN POLYELECTROLYTE

Steady-state voltammograms at a microdisk electrode are used to measur e the diffusion coefficient (D) and standard heterogeneous rate consta nt (k(s)) of ferrocene in polyelectrolyte PEG.MClO(4). The diffusion c oefficient and standard heterogeneous rate constant of ferrocene are b oth smaller in polymer solvents than in monomeric solvents. The D and k(s) of ferrocene have been estimated in PEG containing different conc entrations and cations of supporting electrolytes, and the dependencie s of D and k(s) on temperature have been observed. These results show that the D and k(s) of ferrocene increase with increasing temperature in polyelectrolyte, and with increasing cation radius of supporting el ectrolyte, eg D and k(s) increase in the order Bu(4)NClO(4) > NaClO4 > LiClO4. On the other hand, D and k(s) increase with decreasing concen tration of supporting electrolyte. The dependence of the half-wave pot ential (E(1/2)) on the concentration of the supporting electrolyte is also observed. E(1/2) shifts in the negative direction as the concentr ation of supporting electrolyte increases. (C) 1997 Elsevier Science L td.