Highly Crystalline Mesoporous Titania Loaded with Monodispersed Gold Nanoparticles: Controllable Metal-Support...

We report the syntheses of mesoporous Au/TiO₂ hybrid photocatalysts with ordered and crystalline frameworks using co-assembly of organosilane-containing colloidal amphiphile micelles (CAMs) and poly(ethylene oxide)-modified gold nanoparticles (AuNPs) as templates. The assembled CAMs can convert to inorganic silica during calcination at elevated temperatures, providing extraordinary thermal stability to preserve the porosity of TiO₂ and the nanostructures of AuNPs. Well-defined AuNPs supported within mesoporous TiO₂ (Au@mTiO₂) can be prepared using thermal annealing at temperatures up to 800 °C. High-temperature treatment (≥500 °C) under air is found to not only improve the crystallinity of TiO₂ but also induce oxidative strong metal-support interactions (SMSIs) at Au/TiO₂ interfaces. For oxidative SMSIs, the surface oxidation of AuNPs can generate positively charged Au^δ+ species, while TiO₂ gets reduced simultaneously. Using photocatalytic oxidation of benzyl alcohol as a model reaction, Au@mTiO₂ calcined at 600 °C for 12 h exhibited the best activity under UV irradiation, while Au@mTiO₂ calcined at 600 °C for 2 h showed the best activity under visible light. The delicate balance between the crystallinity and porosity of TiO₂ and the SMSIs at Au-TiO₂ interfaces is found to impact the photocatalytic activity of these hybrid materials.