Ordered mesoporous Ag–TiO2–KIT-6 heterostructure: synthesis, characterization and photocatalysis

Ordered mesoporous Ag–TiO2–KIT-6 heterostructured nanocrystals were successfully synthesized by a template-based method, where a layer of TiO2 and Ag2O nanoparticles were deposited on cubic (Ia3d) silica (KIT-6) in an orderly manner; at the same time, the formed Ag2O nanoparticles were photolyzed to metallic Ag nanoparticles. Our results show that Ag–TiO2–KIT-6 is an ordered mesoporous composite material, which is composed of Ag–TiO2 heterostructures and the amorphous KIT-6 template. In addition, Ag–TiO2–KIT-6 possesses the highest photocatalytic activity among the as-synthesized photocatalysts, which can be attributed to the Ag–TiO2 heterojunctions and the excellent texture: (1) Ag–TiO2 heterojunctions improve the separation of photogenerated electron–hole pairs due to the potential energy differences between Ag and TiO2 nanocrystals, thus enhancing the photocatalytic activity; (2) the Ag–TiO2–KIT-6 sample possesses a high BET surface area and a large number of ordered pore channels, which facilitate adsorption and transportation of dye molecules, also leading to higher photocatalytic activity. It was also found that the Ag–TiO2 heterostructure plays a more important role in enhancing the photocatalytic activity than high BET surface area.