Real-Time Observation of the Defect Dynamics in Working Au/CeO2 Catalysts by Combined Operando Raman/UV-Vis Spectroscopy

Supported gold catalysts are highly active for a variety of reactions including low-temperature CO oxidation. It has been shown that reducible support materials, e.g., ceria or titania, may significantly alter the catalytic performance. In this contribution, we pro-vide the;first direct evidence for ceria (CeO2) support dynamics and its relevance in Au/CeO2 catalysts during room temperature CO oxidation. In particular, combined operando Raman and UV-vis spectroscopy are employed to monitor the surface and subsurface defect dynamics of ceria quantitatively and in real time. The results clearly show a dependence of catalytic activity on the reduction state of the ceria support. In fact, the prereduced CeO2 catalyst support increases the activity during CO oxidation initially by 100%. The reduction is not limited to the CeO2 surface but also affects the CeO2 subsurface due to oxygen mobility and charge transfer in CeO2-x. Our results highlight the enormous importance of the support properties for a mechanistic understanding of oxidation reactions over metal/ceria catalyst materials.