The size-controlled synthesis of monodisperse spherical mesoporous TiO2 particles and high dispersions of Pt, Pd, and Ag clusters on their surfaces

Monodisperse spherical mesoporous TiO2 particles with controlled sizes are synthesized with a simple sol–gel approach from a mixture of poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) triblock copolymer, titanium isopropoxide, and 2,4-pentanedione in aqueous solution. We find that a low concentration of surfactant dissolved in the aqueous solution results in the synthesis of large particles (approx. 2200 nm) with a broad size distribution, but that a high surfactant concentration produces smaller particles (approx. 1100 nm) with a narrow size distribution. FE-SEM and HR-TEM images reveal that the aggregation of the anatase nanocrystalline phase results in the formation of micrometer-size mesoporous TiO2 with a well-defined spherical morphology. Our BET and BJH analyses show that the surface areas (above 213.9 m2 g−1) and average pore sizes of the mesoporous TiO2 materials increase with increases in the calcination temperature: 6.1 nm (400 °C), 7.0 nm (500 °C), and 10.1 nm (600 °C). The photocatalytic activities of these materials in the degradations of methylene blue in aqueous solution and acetaldehyde in the gas phase are higher than that of the Degussa P25 TiO2. Furthermore, the pores of mesoporous TiO2 can be used as nanoscale reactors, so nanosized metal clusters of Pt, Pd, and Ag can be deposited onto the surface of mesoporous TiO2 with an incipient-wetness method. The nanosized Pt, Pd, and Ag clusters (approx. 20–50 nm) are highly dispersed on the surface of the mesoporous TiO2.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Monodisperse spherical mesoporous TiO2 particles were synthesized. ► The mesoporous TiO2 size decreased with an increase in the surfactant concentration. ► The mesoporous TiO2 exhibited higher photocatalytic activities than the P25 TiO2. ► The nanosized Pt, Pd, and Ag clusters were highly dispersed on the TiO2 surface.