Influence of re-activation and ongoing CO oxidation reaction on the chemical and electronic properties of Au on a Au/CeO2 catalyst: A XANES study at the Au LIII edge

The influence of oxidative/reductive pretreatment, oxidative re-activation and ongoing CO oxidation on the chemical/electronic properties of a 4.5 wt.% Au/CeO2 catalyst was investigated by in operando X-ray absorption spectroscopy at the Au LIII edge. Experimental data on the electronic structure and the size of the Au nanoparticles are correlated with findings from kinetic and deactivation measurements. The results of this study show that oxidative re-activation as well as reductive and oxidative pretreatment significantly affect the Au electronic structure and, in consequence, the catalytic properties. Independent of the type of the treatment, however, the Au nanoparticles rapidly reach a metallic state during reaction, both after oxidative pretreatment and after oxidative re-activation, and can therefore not be responsible for the long-term deactivation of the catalyst. Correlations between electronic/chemical structure, evaluated in a semi-quantitative model, and the catalytic performance are discussed.