SO2 oxidation on glassy carbon electrodes: kinetics and mechanistic insights

SO2 oxidation reaction (SO2OR) is an interesting alternative oxidation reaction to enhance the green hydrogen production by water electrolysis. This reaction was already extensively investigated in the literature, using metallic electrocatalysts. In the present work, we investigate this reaction on a carbon electrode, providing a lower overpotential than oxygen evolution, and a precious metal-free electrode. Using classic electrochemical techniques, such as polarization curves and cyclic voltammetry, we could obtain information regarding the presence of two oxidation processes, one around 0.70 VRHE, and another at a more positive potential. The second process was observed to be dependent on the scan rate and was not observed at higher ratios. This suggested that the product of this first process reacted chemically before being further oxidized. This intermediate could also be reduced at these higher rates. A mechanism was proposed based on the adsorption dependence and the potential window of these reactions.