Voltammetry of electroactive oil droplets. Part I: Numerical modelling forthree mechanistic models using the dual reciprocity finite element method

Diffusion problems encountered for the case of electrochemical conversion o f microdroplets of an electroactive oil deposited on an electrode are studi ed by the dual reciprocity finite element simulation method (DRM). Three pl ausible mechanistic models are compared. For a microdroplet of electroactiv e material A) the electrochemical reaction commences from the oil-electrode surface interphase; B) there is rapid charge conduction over the droplet s urface so that ion insertion occurs from the droplet-aqueous electrolyte in terface; C) the electrochemical reaction occurs only at the three phase bou ndary oil-aqueous electrolyte-electrode. Cyclic voltammograms and potential step transient responses are simulated. The dimensionless peak current and peak separation as a function of dimensionless scan rate are presented and a comparison of the three mechanistic models shows distinctly different be haviors. The normalized transient currents as a function of normalized time are given and compared for the three mechanistic models. The results provi de a clear basis for the mechanistic characterization of real systems in te rms of the three models considered.