Structure Sensitivity of Au-TiO₂ Strong Metal-Support Interactions

Strong metal-support interactions (SMSI) is an important concept in heterogeneous catalysis. Herein, we demonstrate that the Au-TiO₂ SMSI of Au/TiO₂ catalysts sensitively depends on both Au nanoparticle (NP) sizes and TiO₂ facets. Au NPs of ca. 5 nm are more facile undergo Au-TiO₂ SMSI than those of ca. 2 nm, while TiO₂ {001} and {100} facets are more facile than TiO₂ {101} facets. The resulting capsulating TiO_2-x overlayers on Au NPs exhibit an average oxidation state between +3 and +4 and a Au-to-TiO_2-x charge transfer, which, combined with calculations, determines the Ti:O ratio as ca. 6:11. Both TiO_2-x overlayers and TiO_2-x -Au interface exhibit easier lattice oxygen activation and higher intrinsic activity in catalyzing low-temperature CO oxidation than the starting Au-TiO₂ interface. These results advance fundamental understanding of SMSI and demonstrate engineering of metal NP size and oxide facet as an effective strategy to tune the SMSI for efficient catalysis.