Modification of Au/TiO2 Nanosystems by SiO2 Monolayers: Toward the Control of the Catalyst Activity and Stability

The activity and stability of Au/TiO 2 catalysts depend on several different factors such as the anchoring strength of the Au particles at the TiO 2 surface, the particle sintering, and the surface mobility of individual gold atoms and/or gold particles. Au/TiO 2 catalysts can be made resistant to sintering by atomic layer deposition (ALD) of a layer of SiO 2 onto the catalysts. In this study, first-principles density-functional calculations are used to investigate how the stability of Au nanoparticles is modified when a partial monolayer of SiO 2 is deposited on a Au/TiO 2 catalyst. We find that SiO 2 structures deposited on a pure TiO 2 substrate exhibit lattice-mismatch instabilities that result in the formation of additional strong anchoring sites for Au atoms/nanoparticles. An atomic-scale roughness introduced by a partial monolayer of SiO 2 can slow the atomic surface diffusion and inhibit Au nanoparticle growth/sintering, in agreement with previous experimental results.