SO2 electrooxidation reaction on Pt single crystal surfaces in acidic media: Electrochemical and in situ FTIR studies

SO2 is a poisonous and anthropogenic gas generated by fossil fuel burning due to the common presence of S-containing contaminants in oil and coal. As a strategy to handle this pollutant and to increase H2 generation, the electrocatalytic SO2 oxidation reaction (SO2OR) is considered. In this way, SO2 is converted to H2SO4, while hydrogen gas is generated at the cathode. To better understand the mechanism and its dependence on the surface crystallography and electrolyte composition, electrochemical and in situ spectroscopic measurements using Pt single crystal electrodes were performed. The crystallographic orientation of the electrode is shown to be critical not only to the SO2OR activity but also to the resulting mechanism. The Pt(100) face is found to be the most active electrode in both H2SO4 and HClO4 aqueous electrolytes, and S2O62− appears as a key intermediate for the mechanism. Volcano plots, drawn considering the Stark tuning slope as a quantity proportional to the adsorption energy, show the importance of S2O62− in the electrode catalytic activity.