(728e) Reduction of Gold Species and Changes in Ce3+/Ce4+ Surface Ratio During CO-PROX Deactivation Catalyzed by Aux/CeO2

The activity and deactivation of Au(x)/CeO2 catalysts in the PROX reaction were measured during long-term experiments. The activity and deactivation patterns are complex, and it appears that deactivation is linked to an alteration of the redox cycle of the ceria, besides possible effects caused by the changes in the distribution of Au species. Our analysis of Au/CeO2 catalysts shows the presence of Au0 and Aun+ species. They were identified based on UV-vis DRS, XPS and XANES spectra of catalysts before and after they were used in reaction. During in-situ DRS-UV-vis studies, the increase of metallic Au was observed via the gold surface plasmon. The support presented changes in its band gap energy. The activity of samples during CO-PROX was closely linked to changes in Au species and in Ce3+/Ce4+ surface ratio. As Ce3+ oxidize during PROX the amount of reactive oxygen available for the reaction decreases and an important fraction of the Au species tend to remain in a reduced state.