An Investigation of Electrode Materials for the Anodic Oxidation of Sulfur Dioxide in Concentrated Sulfuric Acid

The kinetic studies and electrochemical evaluation of catalysts for the oxidation reaction have been carried out in concentrated (50 weight percent) sulfuric acid solutions using the steady‐state potentiostatic method and cyclic voltammetry. Palladium and palladium oxide have been identified to be better catalysts than platinum for this reaction. The polarization potential for oxidation on a preanodized Pd anode decreases with increasing temperature, while the reaction mechanism is independent of temperature. The electrochemical oxidation of commences at an anodic potential where the formation of adsorbed oxygen‐containing species is initiated. On the Pt, Ru, Ir, and Rh anodes, the chemical transformation of the adsorbed species to metal oxides at higher potentials creates passivated layers which partially cover the electrode surface and inhibit the oxidation reaction.