The high speed channel electrode applied to heterogeneous kinetics: the oxidation of 1,4-phenylenediamines and related species in acetonitrile

Abstract

The application of the high-speed microband channel electrode to the study of the heterogeneous electron transfer kinetics of the oxidation of some N-substituted phenylenediamines is described. Experiments to investigate the standard electrochemical rate constant, k 0, of the oxidation of 1,4-phenylenediamine (PPD), N, N-dimethyl-1,4-phenylenediamine (DMPD), and N, N-diethyl-1,4-phenylene-diamine (DEPD) in acetonitrile solutions containing 0.10 M tetrabutylammonium perchlorate (TBAP) are reported for 2.5 and 5 μm platinum microband electrodes using a range of centre-line velocities from 12 to 25 m s −1. The measured values of k 0 for PPD, DMPD, and DEPD are 0.84±0.16, 3.15±0.30 and 1.64±0.25 cm s −1, respectively. The respective formal oxidation potentials are also found to be 0.287±0.002, 0.245±0.001, and 0.208±0.003 V (all measured vs. Ag). Experiments are also presented using “fast scan” cyclic voltammetry to obtain measurements of the heterogeneous rate constants for PPD, DMPD and DEPD to compare between the steady-state channel electrode and the ‘established’ transient methodologies. Scan rates in the range 10 2–10 4 V s −1 were used to measure peak separations with the resulting k 0 values of 0.51±0.05, 1.89±0.10, and 1.28±0.20 cm s −1, respectively. The use of steady-state voltammetry obviates the need for capacitative corrections, perhaps suggesting a greater reliability in the resulting data.