The oxidation of hydroxylamine on Au electrodes in aqueous phosphate buffer solutions (pH 7) was examined using electrochemical and in situ infrared reflection absorption spectroscopy techniques. Polarization curves recorded with a rotating Au disk electrode showed that the onset of NH 2OH oxidation occurs at ca. 0.0 V vs SCE, reaching a well-defined peak at a disk potential, Edisk peak, ca. 0.2 V vs SCE. Plots of the disk current, i disk, at Edisk peak vs ω 1/2 were linear with a close to zero intercept. Measurements in which E disk of the rotating ring-disk electrode was scanned, while E ring was fixed at a value negative enough for solution phase NO to undergo reduction, yielded plots of i ring vs E disk, which mirrored the peak found for i disk and thus was consistent with NO being one of the predominant products of NH 2OH oxidation. In situ infrared measurements provided evidence for N 2O being produced at the same onset potential of NH 2OH oxidation. The disk polarization curves could be reproduced by theoretical simulations involving an EEECE mechanism in which nitrite, one of the products of NH 2OH oxidation, reacts with NH 2OH yielding an electrochemically inert species. In accordance with theory, plots of i disk at Edisk peak as a function of [NH 2OH] bent downward as [NH 2OH] increased.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films