Mass-Transport-Corrected Transfer Coefficients: A Fully General Approach

The transfer coefficient (or, equivalently, the Tafel slope) is an experimentally measurable parameter defined as the change in the logarithm of the current density as a function of the applied potential, where the current density has been corrected (jcorr) for changes in the concentration of the reagent at the interface. For some electrode geometries (such as the rotating disc or a micro hemispherical electrode) where the electroactive interface is uniformly accessible and the mass-transport is at steady-state, these changes in concentration can be corrected for analytically. Correcting for the depletion of the reagent significantly increases the range over which Tafel analysis can be used to accurately yield information regarding the electron-transfer process. The important question arises, therefore, for non-uniformly accessible electrodes or for a system not at steady state, such as often encountered with disc electrodes, how can the experimentally measured electrochemical flux be rigorously corrected for to account for the changes in the surface concentration of the reagent? This work presents a simple simulation technique that allows the voltammetry of a disc to be "mass-transport"-corrected without recourse to the use of analytical approximations.