A Combined Experimental and Theoretical Study On CO Oxidation Mechanism Over Au38-Derived Au/TiO2 Catalyst

Two decades after supported Au clusters were first reported to be active for CO oxidation at low temperatures, the activity of these catalysts is still under investigation.  These catalysts have been studied on a variety of metal oxide supports like CeO₂, TiO₂, ZrO₂, Al₂O₃, Fe₂O₃, Co₃O₄, and SiO₂. However, the most commonly studied catalyst for CO oxidation remains Au supported on TiO₂ due to its higher activity.

Au₃₈ clusters were synthesized using our previously reported method and impregnated on a mesoporous TiO₂ support to give Au₃₈/TiO₂ catalyst. This catalyst was treated to remove the thiol ligands which were present as a result of thiol etching protocol used to synthesize the clusters. Three kinds of experiments were performed on the Au/TiO₂ catalyst in a plug-flow fixed-bed reactor and an in situ DRIFTS cell at room temperature: a) CO flow for 5 min. followed by He flushing for 10 min, b) CO oxidation with ¹⁶O₂ for 60 min., and c) CO oxidation with ¹⁸O₂ for 60 min. These experiments suggest that the oxidation of CO occurs via a Mars van Krevelen of redox mechanism.