Boosting SO2 electrocatalytic oxidation reaction on highly dispersed subnanometric Au/TiO2 catalyst

The increase in the consumption of fossil fuels led not only to the increase of atmospheric CO2 level, but also to the increment in sulfur pollutants production, such as SO2. The electrochemical SO2 oxidation reaction (SO2OR) was already shown to be efficiently catalyzed by Au and, to further develop the technological knowledge in this field, the application of nanostructured Au catalysts is highly desirable. Herein we present a highly dispersed subnanometric Au/TiO2 catalyst as active material for SO2OR. The Tafel analysis revealed a change in the reaction mechanism and a substantial increase of the electrocatalytic reaction activity compared to bulk Au, even at conditions where bulk Au presented low activity, such as H2SO4 electrolyte. Electrochemical impedance spectroscopy (EIS) results led to the conclusion that TiO2 is also involved in the reaction, since not only the oxide time constant changes with the applied potential but also adsorbed intermediates were observed. This EIS response is probably related to the Au/TiO2 interface, which reflects on the oxide time constant.