Oxidation of Hydroxylamine on Gold Electrodes in Aqueous Electrolytes: Rotating Ring-Disk and In Situ Infrared Reflection Absorption Spectroscopy Studies

Abstract

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 NH2OH oxidation occurs at ca. 0.0 V vs SCE, reaching a well-defined peak at a disk potential, E disk peak, ca. 0.2 V vs SCE. Plots of the disk current, i disk, at E disk peak vs ω1/2 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 NH2OH oxidation. In situ infrared measurements provided evidence for N2O being produced at the same onset potential of NH2OH oxidation. The disk polarization curves could be reproduced by theoretical simulations involving an EEECE mechanism in which nitrite, one of the products of NH2OH oxidation, reacts with NH2OH yielding an electrochemically inert species. In accordance with theory, plots of i disk at E disk peak as a function of [NH2OH] bent downward as [NH2OH] increased.

Hydroxylamine Oxidation on Polycrystalline Gold Electrodes in Aqueous Electrolytes: Quantitative On‐Line Mass Spectrometry under Forced Convection

“…Some of the on‐line DEMS data involving gases other than N 2 in neutral media are in qualitative agreement with earlier results obtained using other techniques. In particular, the onset of N 2 O detection coincides with the onset for the oxidation of NH 2 OH as reported earlier in our laboratory using in situ FTIR, for which the cross sections for absorption are very high. However, at least two factors complicate a more quantitative analysis of the results presented in this work.…”

“…In addition, NH 2 OH reacts with NO 2 − (aq) in solution phase to yield N 2 O as one of the products, and thus contributes to its DEMS signal. Although it is, in principle, possible to use numerical simulations to account for this process, as we reported in earlier work for a rotating disk electrode, the wall jet characteristics of our present system would make such calculations non trivial and, as such, any determination of faradaic efficiencies for gases other than N 2 would be subject to rather large uncertainties.…”

“…Complementary experiments involving in situ normalized IRAS spectra yielded a prominent peak centered at 2230 cm À 1 , characteristic of nitrous oxide, N 2 O, at a potential very close to the onset of NH 2 OH oxidation, the intensity of which reached a maximum at about the same potential as that found the dynamic polarization recorded with a rotating disk electrode in separate measurements in the same electrolyte. [4] Based on the electrochemical and spectroscopic information, and theoretical simulations, the observed behavior could be accounted for by an EEECE mechanism in which NO 2 À (aq), one of the products of NH 2 OH oxidation, reacts with NH 2 OH yielding an electrochemically inert species. In related studies, the groups of Koper and Feliu have shown that nitrite, NO 2 À , can be reduced to N 2 on quasi perfect Pt(100) electrodes in alkaline media.…”

Toward point-of-care management of chronic respiratory conditions: Electrochemical sensing of nitrite content in exhaled breath condensate using reduced graphene oxide

“…The electrochemical detection of nitrite is based on either the oxidation or reduction of nitrite [30][31][32] . Nitrite oxidation-based methods with a final product of NO 3 are usually preferred because the presence of interfering molecules (such as oxygen) during reduction can be avoided 33 .…”

Electrocatalytic oxidation of nitrite using metal-free nitrogen-doped reduced graphene oxide nanosheets for sensitive detection

“…The electrochemical methods are desirable owing to the ease of operation, real-time detection, rapid response, and high sensitivity. In general, the electrochemical methods result from either anodic oxidation or cathodic reduction of nitrite on the surfaces of chemically modified electrodes [9][10][11]. The anodic oxidation of nitrite is desirable because nitrate ( − NO 3 ) is the ultimate product without interference, but occurs at relatively high overpotential [12].…”