Mechanistic Insight into Sulfide-Enhanced Oxygen Reduction Reaction Activity and Stability of Commercial Pt Black: An in Situ Raman Spectroscopic Study

Adsorption of sulfur-containing species on a catalyst surface has long been treated as an unwelcoming process in catalysis because it is frequently related to poisoning of the catalyst. However, we reported recently that sulfide adsorption of moderate coverage on commercial carbon-supported Pt electrocatalyst could substantially enhance the oxygen reduction reaction (ORR). Herein, we not only reproduced the sulfide-adsorption-enhanced ORR on a different type of commercial Pt electrocatalyst, Pt black, but we also discovered that the sulfide adsorption enhanced the stability of the Pt black as well. In situ surface-enhanced Raman spectroscopic (SERS) studies of a roughened Pt surface in a flow cell strongly suggest that the enhanced ORR activity and stability was most likely due to the fact that the sulfide adsorption made the Pt surface more oxidation resistant.