Electrochemical behaviour of aqueous SO2 at polycrystalline gold electrodes in acidic media: a voltammetric and in situ vibrational study: Part 1. Reduction of SO2: deposition of monomeric and polymeric sulphur

Quijada, C. and Huerta, F.J. and Morallon, E. and Vazquez, J.L. and Berlouis, L.E.A. (2000) Electrochemical behaviour of aqueous SO2 at polycrystalline gold electrodes in acidic media: a voltammetric and in situ vibrational study: Part 1. Reduction of SO2: deposition of monomeric and polymeric sulphur. Electrochimica Acta, 45 (11). pp. 1847-1862. ISSN 0013-4686

Abstract

The electro-reduction of SO2 has been monitored by using cyclic voltammetry, FT-IR spectroscopy and SER spectroscopy. Prior to the bulk reduction, SO2 is reduced to yield a monomeric sulphur adlayer at a maximum coverage of about 0.25. The sulphur adlayer undergoes a reversible redox surface process at E<0.0 V (RHE), which implies a change in the frequency of the Au---S stretching mode from 270 to 300/310 cm−1. In the potential region encompassing the bulk reduction voltammetric peak, infrared spectra display a band at 2585 cm−1 attributable to a S---H vibration from a soluble species. Accordingly, H2S or H2Sx were proposed as tentative bulk reduction products. In positive sweeps a broad anodic wave develops between 0.2 and 0.6 V that leaves polymeric sulphur species adsorbed at multilayer level, with a S---S stretching mode at 460 cm−1 and a S---S---S bending vibration at 218 cm−1. Multilayer sulphur can be removed reductively under a sharp cathodic peak. According to literature of the S(-II)/Au system, removal proceeds to yield soluble S(-II) species, via intermediate polysulphides.

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