The electrochemical oxidation of sulfite on gold: UV-Vis reflectance spectroscopy at a rotating disk electrode

Yuriy V. Tolmachev, Daniel Alberto Scherson

Research output: Contribution to journalConference article

24 Citations (Scopus)

Abstract

Certain aspects of the electrochemical oxidation of sulfite in buffered, mildly acidic aqueous solutions (pH 5.23) have been examined using in situ near normal incidence UV-Vis reflectance spectroscopy (NNI-UVRS) at a Au rotating disk electrode (RDE). The dependence of the limiting current, ilim, on the rotation rate of the RDE was found to display classical Levich behavior up to potentials well within the range in which Au forms a surface oxide in the neat (sulfite-free) supporting electrolyte. However, simultaneous in situ NNI-UVRS measurements performed at λ = 500 nm during sulfite oxidation failed to show any evidence for the presence of oxide on the Au surface within that entire potential range. Polarization of the Au RDE at more positive potentials led to a sudden drop in ilim, ca. an order of magnitude, which correlated with an abrupt decrease in the intensity of the reflected light, consistent with formation of (one or more forms of) Au oxide on the surface. On the basis of these and other observations a model has been proposed in which sulfite reacts chemically with adsorbed oxygen on the surface (oxygen atom transfer) in the region that precedes partial inhibition. As the potential is increased, adsorbed oxygen undergoes Au-O place exchange forming two-dimensional nuclei on the surface, which undergo rapid (autocatalytic) growth, covering an area large enough to block significantly sulfite oxidation.

Original languageEnglish
Pages (from-to)1315-1319
Number of pages5
JournalElectrochimica Acta
Volume49
Issue number8
DOIs
Publication statusPublished - 2004 Mar 30
Externally publishedYes
EventTrends in Surface Electrochemistry: From Single Crystals to - Alicante, Spain
Duration: 2003 Mar 22003 Mar 6

Keywords

  • Electrochemical oxidation
  • Rotating disk electrodes
  • UV-Vis reflectance spectroscopy

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Electrochemistry

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