Incorporating electrode kinetics into the convolutive modeling of reactions at planar, cylindrical and spherical electrodes

Convolutive modeling provides a valuable alternative to digital simulation as a means of predicting the outcome of a voltammetric experiment, for comp arison with the laboratory version. Methods based on either of two conjugat e functions are described, differing in the direction that the convolution takes. Other than the requirement of uniform accessibility of the electrode surface, convolutive modeling places few restrictions on the range of expe riments that may be modeled. The electrode reaction may have any degree of reversibility and may, or may not, be coupled to a first-order chemical pro cess. The diffusivities of the reactant and product may be equal or unequal . The current may be the controlled electrical variable, or the current may be monitored in an experiment in which the potential is controlled. A rang e of experimental techniques is addressed in this article, including curren t-reversal chronopotentiometry and cyclic voltammetry without and with a fo llowing chemical reaction. Algorithms are reported for each of the two conv olution routes. Examples treated in detail include both planar and spherica l diffusion fields. The heterogeneous rate constant was varied in all insta nces, reversible, quasi-reversible, and near-irreversible cases bring consi dered. Differences between the predictions of the two routes was found to b e insignificant, both of the theoretical voltammograms agreeing excellently with analytical formulas, where these are available for comparison. In the case of quasi-reversible cyclic voltammetry, the prediction of the convolu tive model was evaluated by global analysis: the input parameters were reco vered with only minor discrepancies. (C) 2001 Elsevier Science Ltd. All rig hts reserved.