Masakazu Anpo

Structural evaluation and photocatalytic properties of Pt-supported titanate nanotubes

Pt nanocrystal-supported titanate nanotubes as a photocatalyst were prepared by hydrothermal treatment and subsequent heat-treatment in H2 atmosphere (H2 reduction) of a mixture of these titanate nanotubes and H2PtCl6. TEM results showed that Pt nanoparticles (a few nm in diameter and 5 to 10 nm in length) with good crystallinity were entrapped inside titanate naotubes and were closely precipitated on the surface of titanate nanotubes. These Pt nanocrystal-supported titanate nanotubes possessed the high ability for HCHO decomposition.

Development of Well-Defined Visible Light-Responsive TiO2 Thin Film Photocatalysts by Applying a RF-Magnetron Sputtering Deposition Method

TiO2 thin film photocatalysts which can work under visible light irradiation were successfully developed in a single process by applying a RF magnetron sputtering (RF-MS) deposition method. The TiO2 thin films prepared at higher than 773 K showed efficient absorption of visible light, while the TiO2 films prepared at around 473 K were highly transparent. This clearly means that the optical properties of these films, which absorb not only UV but also visible light, can be controlled by the preparation conditions using the RF-MS deposition method. These visible light-responsive films were found to exhibit effective photocatalytic reactivity at room temperature for the decomposition of NO and oxidation of acetalydehyde with O2. Various characterization studies showed that orderly aligned columnar TiO2 crystals of ca. 100 nm could be observed only for the visible light-responsive TiO2 thin films. Such unique structural factors are considered to be essential in modifying the electronic properties of the TiO2 semiconductors, enabling the efficient absorption of visible light. Moreover, crystalline TiO2 thin films could be prepared on thermally unstable polycarbonate substrates at 353 K by using this RF-MS deposition method.

Improvement of the hydrothermal stability of MCM-48 mesoporous molecular sieves

This is a review of our recent reports about improving the hydrothermal stability of MCM-48 mesoporous molecular sieves and the related works done by other groups. It presents the different effects of direct addition of various anions, including F−, SO42−, NO3− and Cl−, on the improvement of the hydrothermal stability of MCM-48. The different effects of anions on the improvement of the hydrothermal stability and the critical factors influencing the formation of hydrothermally stable MCM-48 are also explained by careful analysis and discussion.

Preparation of TiO2 nano-particle photocatalysts by a multi-gelation method: the effect of pH change

TiO2 photocatalysts were prepared by a multi-gelation method and the effect of the changes in the pH during the pH swing times, i.e., by a controlled pH swing, on the morphology of the TiO2 particles was investigated. The photocatalytic properties of the TiO2 catalysts prepared by controlled pH swing were compared with TiO2 particles prepared without adjusting the pH during the swing times. The photocatalytic degradation reaction of these TiO2 catalysts was investigated by comparing their effectiveness in 2-propanol oxidation. The experimental results showed that the TiO2 photocatalysts prepared without adjusting the pH performed better in controlling the important parameters of the catalysts such as particle size, surface area, anatase/rutile phase ratio and pore size, as well as pore volume than the TiO2 photocatalysts prepared by a controlled pH swing method.

Photocatalytic Hydrogen Production from Water on Visible Light-Responsive TiO2 Thin Films Under Solar Light Irradiation

The recent progress in the photocatalytic decomposition of water by visible light-responsive TiO2 (Vis-TiO2) thin film photocatalysts is reviewed here. Special attention is focused on the separate evolution of H2 and O2 from water using Vis-TiO2 thin films prepared by a radio-frequency magnetron sputtering method. These Vis-TiO2 thin films were found to act as efficient photocatalysts for the decomposition of water with the separate evolution of H2 and O2 from H2O under visible or solar light irradiation.