Theoretical Clarification of the Coexistence of Cl Effects on Au/TiO2: The Interaction between Au Clusters and the TiO2 Surface, and the Aggregation of Au Clusters on the TiO2 Surface

Abstract

Abstract Interactions between nanosized Au cluster models (Au rods, ribbons, and film) and rutile TiO2 (110) modeled surfaces (stoichiometric: sTiO2, reduced: rTiO2, and Cl-adsorbed: Cl-rTiO2) were determined using density functional theory. The Au–Au bonds are weakened and the Au–Ti bonds are strengthened because the oxygen defect sites in rTiO2 donate electrons to the nanosized Au models. These interactions suppress the aggregation of the nanosized Au models on the rTiO2 surface. However, Cl atoms are more strongly adsorbed at the oxygen defect site of rTiO2 than Au. The amount of transferred electrons from Cl-rTiO2 to the nanosized Au models is smaller than that of rTiO2. Notably, the Au/Cl-rTiO2 interactions are smaller than the Au/sTiO2 interactions in two- and three-dimensional Au clusters. Thus, Cl atom adsorption onto the oxygen defect site decreases the Au/TiO2 interaction, and the aggregation of the nanosized Au models easily proceeds on Cl-rTiO2. Hence, the Cl atom adsorption onto the oxygen defect site of the TiO2 surface can be assumed as a reason for the residual Cl enhancement of Au aggregation on the TiO2 surface during Au/TiO2 catalyst preparation.