Surface Dynamics of Au/CeO₂Catalysts during CO Oxidation

The catalytic activity of gold-based catalysts for CO oxidation is influenced by gold particle size, dispersion, and redox properties of the support. The nature of the active site (gold oxidation state) and its modification along the course of the reaction are under discussion. In this work, we studied the modifications of a Au/CeO 2 catalyst in the presence of gas-phase CO by simultaneous in situ diffuse reflectance infrared Fourier transform mass spectrometry (DRIFT-MS) in isothermal conditions. Redox processes involving surface hydroxyl groups, gold atoms, and gas-phase CO molecules play a determinant role in surface gold dynamics. The interaction of CO with the catalyst surface results in the evolution of CO 2 and H 2 through both the decomposition of the formate species and the formation of the [Au(CO) 2 ] + species, which accounts for the redispersion of gold atoms. The identification of the involved surface species by DRIFT lets us state that a deep reduction of the surface (oxygen vacancy creation) changes the gold dispersion and migration of oxygen atoms to the surface, generating an oxidized gold species. This result is also confirmed by XRD, where a decrease in the intensity of all metallic gold diffraction peaks and the relative intensity among them is evidenced in the used catalyst. Therefore, this work provides evidence for the surface dynamics of gold in this Au/CeO 2 catalyst and hence provides clues for understanding the modification of the catalytic activity of gold catalysts under cyclic operations.