Structure-Sensitivity of Au-TiO2 Strong Metal-Support Interaction.

Strong metal-support interaction (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 ∼5 nm are more facile undergo Au-TiO2 SMSI than those of ∼2 nm, while TiO2 {001} and {100} facets are more facile than TiO2{101} facets. The resulting capsulating TiO2- x overlayers on Au NPs exhibit an average oxidation state between +3 and +4 and a TiO2- x -to-Au charge transfer, which, combined with theoretical calculations, determines the Ti:O ratio as ∼6:11. Both TiO2- x overlayers and TiO2- 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.