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 ha s been studied in an acidic medium by means of cyclic voltammetry and in situ Fourier transform IR (FTIR) spectroscopy. In the potential zon e 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 adso rbate. In situ FTIR spectroscopy yields a band at 1271 cm(-1), which c ould be assigned to adsorbed SO2. However, (bi)sulphate is detected as the only SO2 oxidation product. The generation of S(VI) species occur s during both the forward and the reverse sweeps. The different voltam metric responses obtained in each case are attributed to the oxidation of SO2 on a Pt electrode with different surface states.