The pH Dependence of the Oxidation Reaction of SO_2 at a Platinum Electrode Studied by Voltammetric and In Situ Infrared Spectroscopic Measurements

摘要

The electrooxidation of S(IV)-contained species in the aqueous solution of sodium sulfite at a polycrystalline Pt electrode was studied by cyclic voltammetry and in situ infrared spectroscopy as a function of solution pH (1≤pH≤5). The diffusion-controlled anodic current observed at >0.7 V vs. Ag | AgCl | KCl sat. decreased in the solution of pH larger than 2, and reached a minimum value at pH 5. On the other hand, the activation effect by pre-polarization of the Pt electrode was observed in all of the pH solutions investigated. In situ infrared spectroscopic measurements undertaken during the oxidation reaction indicated that the main oxidation products were S(VI) species assignable either to HSO_4~- or SO_4~(2-).