Chronoamperometric transients at the stationary disk microelectrode

Chronoamperometric transients for diffusion controlled reactions at stationary platinum and gold microelectrodes have been examined. The results are compared with those predicted theoretically for hemispherical electrodes and for disk electrodes. The hemispherical model was found to describe the current-time transients only qualitatively, while excellent agreement was obtained between the theory for a stationary disk and data for the hexacyanoferrate (II)/(III) redox reaction. Equations for mass transport to a stationary disk electrode derived earlier form the basis for graphical methods of analysis of a single current-time transient which permit the simultaneous determination of two of the three parameters electrode radius, diffusion coefficient, and concentration. A plot of I vs 1/sq. rt. t has the advantage of simplicity. A logarithmic analysis (log I-log t) requires data over a greater time range but offers advantages in characterizing electrode geometry. The effects of surface irregularities and electrode sphericity are also discussed.