Analytical theory is developed for heterogeneous ECE reactions occurring at channel electrodes. Simple expressions are presented that allow the ready mechanistic interpretation of experimental data and the deduction of corresponding rate constants. These are shown to be in excellent agreement with numerical simulations and consistent with experiments conducted on the reduction of nitromethane in buffered aqueous solution at Hg/Cu electrodes deposited on a platinum substrate thought to proceed via a heterogeneous ECEEE mechanism. The experimental resolution between heterogeneous and homogeneous ECE processes in general is discussed.

Theory is presented to predict the mass transport limited current flowing at a hydrodynamic microstrip electrode located in a rectangular flow cell under steady state and chronoamperometric conditions. The influence of electrode size is quantified with the relative effects of lateral diffusion, normal diffusion, and axial convection identified. Theory is found to be in good agreement with experimental measurements conducted using the oxidation of tris(4-bromophenyl)amine at a platinum microstrip electrode. The microstrip electrode is seen to exhibit considerably enhanced mass transport characteristics over its macroelectrode equivalent and consequently is proposed as a new tool for the study of electrode reaction mechanisms.

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Theory is developed for heterogeneous ECE reactions occurring at channel electrode that predicts the voltammetric waveshape, as characterized by the half-wave potential and the Tafel slope as a function of the rate of mass transport and the cell geometry. Working surfaces are reported that allow the ready mechanistic interpretation of experimental data and the deduction of corresponding rate constants. Experiments are reported on the reduction of nitromethane in aqueous buffered solution (7 < pH < 9) at platinum electrodes that is thought to proceed via a heterogeneous ECEEE mechanism. Analysis of both waveshape and limiting current data confirm this mechanistic assignment, allowing the following appropriate kinetic parameters to be reported:  heterogeneous rate constant, 0.26 ± 0.07 cm s-1; and standard electrochemical rate constant, 0.13 ± 0.01 cm s-1.

The application of the high-speed channel microband electrode to potential step transient measurements is reported. Potential step experiments, from conditions of no current flows up to a potential value where the mass transport limited current is reached, using the one-electron oxidation of N,N,N‘,N‘-tetramethyl-1,4-phenylendiamine and the one-electron reduction of p-bromonitrobenzene and p-chloronitrobenzene are reported. The applicability of a model in which the dominant mass transport form is by diffusion normal to the electrode and by convection axially through the channel is demonstrated so that axial diffusion effects are negligible. This permits the use of the backward implicit procedure to analyze the experimental transient responses incorporating any kinetic complications, as appropriate. It is shown that homogeneous rate constants of at least 1 order of magnitude higher are accessible by potential step transient measurements for an ECE mechanism as compared to steady-state experiments.