title: On the chemical and electrochemical one-electron reduction of peroxynitrous acid.
abstract: Peroxynitrous acid was reduced by cathodic linear sweep voltammetry at a gold electrode and by iodide at pH 3.2 and 5.6. The cathodic reduction wave was identified by measuring its decay in time, which was the same as observed by optical spectroscopy. The iodide oxidation was followed by optical measurement of the triiodide formation. Both reductions show one-electron stoichiometry, with the product n(alpha)alpha = 0.23 +/- 0.04 from the electrochemical experiments, in which alpha is the transfer coefficient and n(alpha) the number of electrons transferred, and an diiodine yield of ca. 0.5 equiv per equivalent of peroxynitrous acid. The voltammetric reduction was irreversible up to scan rates of 80 V s(-1). Both reductions were pH independent in the range studied. The voltammetric reduction is most likely an irreversible elemental reaction followed by a chemical decay that cannot be observed directly. Because of the pH independence, we conclude that both reductions have a common short-lived intermediate, namely [HOONO]*-. We estimate the electrode potential of the likely ONOOH/ONOOH*- couple to be larger than 1 V. The commonly used electrode potential E degrees (ONOOH, H+/NO2*, H2O) does not describe the chemistry of peroxynitrous acid.
authors.affiliation: Laboratorium für Anorganische Chemie, Department of Chemistry and Applied Biosciences, ETH Zurich, CH 8093 Zurich, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Kurz
authors.forename: Xiuqiong
authors.initials: X
authors.lastname: Zeng
authors.forename: Stefan
authors.initials: S
authors.lastname: Hannemann
authors.forename: Reinhard
authors.initials: R
authors.lastname: Kissner
authors.forename: Willem H
authors.initials: WH
authors.lastname: Koppenol