Composites of small Ag clusters confined in the channels of well-ordered mesoporous anatase TiO2 and their excellent solar-light-driven photocatalytic performance

Small Ag clusters confined in the channels of ordered mesoporous anatase TiO2 have been fabricated via a vacuum-assisted wet-impregnation method, utilizing well-ordered mesoporous anatase TiO2 with high thermal stability as the host. The composites have been characterized in detail by X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption fine structure (XAFS) spectroscopy, N-2 adsorption, UV-visible diffuse reflectance spectroscopy and transmission electron microscopy. The results indicate that small Ag clusters are formed and uniformly confined in the channels of mesoporous TiO2 with an obvious confinement effect. The presence of strong Ag-O interactions involving the Ag clusters in intimate contact with the pore walls of mesoporous TiO2 is confirmed by XAFS analysis, and favors the separation of photogenerated electron-hole pairs, as shown by steady-state surface photovoltage spectroscopy and transient-state surface photovoltage measurements. The ordered mesoporous Ag/TiO2 composites exhibit excellent solar-light-driven photocatalytic performance for the degradation of phenol. This is attributed to the synergistic effects between the small Ag clusters acting as traps to effectively capture the photogenerated electrons, and the surface plasmon resonance of the Ag clusters promoting the absorption of visible light. This study clearly demonstrates the high-efficiency utilization of noble metals in the fabrication of high-performance solar-light-driven photocatalysts.