Revisiting the Au Particle Size Effect on TiO2 Coated Au/TiO2 Catalysts in CO Oxidation Reaction
It is well known that the particle size of Au nanoparticles enormously affects the catalytic activity of supported gold catalysts in many reactions. The origin of the Au particle size effect is still widely debated. In this work, we precisely deposited different thicknesses of ultrathin TiO2 overcoats onto three Au/TiO2 catalysts with Au particle sizes of 2.9 0.6 (Au/TiO2 S) 5.0 0.8 nm (Au/TiO2 M) and 10.2 1.6 nm (Au/TiO2 L) using atomic layer deposition (ALD) High resolution transmission electron microscopy illustrated the Au nanoparticles on these three samples were encapsulated by the TiO2 overcoat. X ray photoelectron spectroscopy measurements showed that the Au nanoparticles remained at metallic state after applying TiO2 ALD overcoat. Diffuse reflectance infrared Fourier transform spectroscopy measurements of CO chemisorption further revealed that the TiO2 overcoat preferentially decorated at the low coordination sites of Au nanoparticles and broadly tuned the population of these sites acces.