The extraction of heterogeneous kinetic parameters from combined chronoamperometric and chronocoulometric data by a multiple regression procedure

Abstract

A new method for extracting kinetic parameters from heterogeneous electrochemical reactions without distortion of the data and with a reliable calculus of uncertainty in the parameters has been devised. It consists of the application of a statistical multivariable regression procedure to combined current ( i)-charge ( q) transient data obtained from the potentiostatic pulse technique. The procedure was tested on theoretical i- q transients, both on pure faradaic data and on faradaic data admixed with Gaussian noise and typical double-layer component values. It was also satisfactorily checked on real systems, i.e. from the typical irreversible Fe 2+ oxidation on a glassy carbon electrode in acidic medium (I), through the “slow” quasi-reversible oxidation of Fe(CN) 4− 6 in neutral aqueous solution on a glassy carbon electrode (II), to the “fast” quasi-reversible N, N, N', N'-tetramethyl- p-phenylendiamine oxidation on a platinum electrode in acetonitrile (III). A method for recovering the diffusion coefficients of electroactive substances from combined kinetic data is also proposed. This method also proved to be a good internal check of the whole procedure.