ELECTROCHEMICAL-BEHAVIOR OF AQUEOUS SO2 AT PT ELECTRODES IN ACIDIC MEDIUM - A VOLTAMMETRIC AND IN-SITU FOURIER-TRANSFORM IR STUDY .1. OXIDATION OF SO2 ON PT ELECTRODES WITH SULFUR-OXYGEN ADSORBED SPECIES

The electrochemical oxidation of aqueous SO2 at platinum electrodes has been studied in an acidic medium by means of cyclic voltammetry and in situ Fourier transform IR (FTIR) spectroscopy. In the potential zone ranging from 0.55 to 1.50 V (vs.RHE), the oxidation reaction of SO2 takes place at a Pt surface initially covered by a sulphur-oxygen adsorbate. In situ FTIR spectroscopy yields a band at 1271 cm(-1), which could be assigned to adsorbed SO2. However, (bi)sulphate is detected as the only SO2 oxidation product. The generation of S(VI) species occurs during both the forward and the reverse sweeps. The different voltammetric responses obtained in each case are attributed to the oxidation of SO2 on a Pt electrode with different surface states.