Photoelectrochemical Reduction ofp-Bromonitrobenzene: Mechanistic Discrimination via Channel Microband Array Voltammetry

Abstract

Two dimensional voltammetry using an array of channel microband electrodes varying in size from ca. 2 mm to under 1 micron in length, has been used to study the photoreduction of p-bromonitrobenzene. In the dark p-bromonitrobenzene is reduced at −1.09 V (vs. SCE). On irradiation with strong white light significant photocurrents flowed which were recorded at flow rates from 2 × 10−3 cm3 s−1 to ca. 0.3 cm3 s−1 at various electrode sizes. Mechanistic analysis of these steady-state measurements is shown to unambiguously rule out an ECEE mechanism but suggests instead that an ECE description is the correct one. The analysis is carried out using a WWW based data analysis centre which uses stored working curves to provide best-fit values for the rate constant of the chemical step and for the mean diffusion coefficient of the species involved.