Noble metal nanoclusters and their in situ calcination to nanocrystals: Precise control of their size and interface with TiO₂ nanosheets and their versatile catalysis applications

In this work, we present a new versatile strategy to prepare noble metal (Au, Ag and Cu) nanoclusters on TiO₂ nanosheets in large scales with exposed (001) facets with controlled size, crystalline interface, and loading amount. By precise in situ calcination, the metal (M = Au, Ag, and Cu) nanocrystals with controllable size and better crystalline interface with the TiO₂ support have been prepared. The potential application of the as-prepared Au, Ag, and Cu nanoclusters on TiO₂ nanosheets as potential heterogeneous catalysts for organic synthesis, such as catalytic reduction of 4-nitrophenol to 4-aminophenol, has been demonstrated. After calcination, Au, Ag, and Cu nanocrystals were found to be proficient cocatalysts for photocatalytic H₂ evolution, particularly the Au cocatalyst. Based on precise high-resolution transmission electron microscopy (HRTEM) and inductively coupled plasma optical emission spectrometry (ICP-OES) analyses, the flexible control of their size and loading amount as well as their intimate contact with the TiO₂ nanosheet enhanced the photocatalytic H₂ evolution activity and the sensitivity of the photocurrent response of the film. Furthermore, this aqueous-directed synthesis of metal nanoclusters on a support will generate further interest in the field of nanocatalysis.