Electroreduction of nitromethane in aqueous solution. A surface indifferent electrocatalytic reaction

The electroreduction of nitromethane in aqueous solution is shown to follow a mechanism of the heterogeneous ECEEE type on gold electrodes as also seen for platinum and other substrates. Moreover, the rate of the chemical step is surprisingly similar, to within less than an order of magnitude, on all surfaces studied. Kinetic isotope measurements show that the chemical step in the reaction sequence is approximately a factor of 2 slower in D2O than in H2O. A mechanism is proposed that accounts for the lack of surface sensitivity and for the observed isotope effect

Voltammetry under high mass transport conditions. The high-speed channel electrode and transient measurements

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

Heterogeneous ECE processes at channel electrodes: Analytical theory. Distinguishing hetero- and homogeneous ECE reactions

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

Heterogeneous ECE processes at channel electrodes: Voltammetric waveshape theory. Application to the reduction of nitromethane at platinum electrodes

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

Electrode processes with coupled chemistry. Heterogeneous or homogeneous chemical reaction? The reduction of nitromethane in basic aqueous solution

The reduction of nitromethane in aqueous solution (pH 8.3) at Au/Hg channel electrodes is suggested, by means of joint electrochemical ESR and voltammetric measurements, to follow an ECEEE mechanism in which the rate determining chemical step is a surface catalysed reaction. Theory characterising heterogeneous ECE (and ECEEE) processes at channel electrodes, studied voltammetrically and with in situ ESR detection, is reported. © 1997 Elsevier Science S.A