Kanji Saito

Remarkable Charge Separation and Photocatalytic Efficiency Enhancement through Interconnection of TiO2 Nanoparticles by Hydrothermal Treatment.

Although tremendous effort has been directed to synthesizing advanced TiO2 , it remains difficult to obtain TiO2 exhibiting a photocatalytic efficiency higher than that of P25, a benchmark photocatalyst. P25 is composed of anatase, rutile, and amorphous TiO2 particles, and photoexcited electron transfer and subsequent charge separation at the anatase-rutile particle interfaces explain its high photocatalytic efficiency. Herein, we report on a facile and rational hydrothermal treatment of P25 to selectively convert the amorphous component into crystalline TiO2 , which is deposited between the original anatase and rutile particles to increase the particle interfaces and thus enhance charge separation. This process produces a new TiO2 exhibiting a considerably enhanced photocatalytic efficiency. This method of synthesizing this TiO2 , inspired by a recently burgeoning zeolite design, promises to make TiO2 applications more feasible and effective.

A controlled spatial distribution of functional units in the two dimensional nanospace of layered silicates and titanates.

The immobilization of functional units in the interlayer spaces of layered silicates and titanates is summarized from the viewpoint of how the spatial distribution of functional units in the interlayer affects the performance of the intercalation compounds. The ways of incorporating controlled amounts of functional units with controlled spatial distribution are also discussed. As a result of controlled spatial distribution of functional units in two-dimensional nanospace, one can achieve improved efficiency of photo-induced events (photoluminescence and photoinduced electron/energy transfer), molecular sieving and substrate/product selective catalytic reactions.

Host–guest chemistry of mesoporous silicas: precise design of location, density and orientation of molecular guests in mesopores

Abstract Mesoporous solids, which were prepared from inorganic-surfactant mesostructured materials, have been investigated due to their very large surface area and high porosity, pore size uniformity and variation, periodic pore arrangement and possible pore surface modification. Morphosyntheses from macroscopic morphologies such as bulk monolith and films, to nanoscopic ones, nanoparticles and their stable suspension, make mesoporous materials more attractive for applications and detailed characterization. This class of materials has been studied for such applications as adsorbents and catalysts, and later on, for optical, electronic, environmental and bio-related ones. This review summarizes the studies on the chemistry of mesoporous silica and functional guest species (host–guest chemistry) to highlight the present status and future applications of the host–guest hybrids.

Hydrogenation of carbon monoxide to form light olefins over zeolite-based iron catalysts

Abstract Zeolite-based iron catalysts promoted with various transition metals were tested by using a reaction gas mixture of CO:H2:Ar=45:45:10 at temperature ranging from 350to 450 ° under pressure varying from; 0.2 to 4.5 MPa. It was found that high selectivity of C2and C3 olefins was obtained with Fe-Ti-V- and Fe-Ti-Mn-zeolite-based catalysts.

h-BN nanosheets as simple and effective additives to largely enhance the activity of Au/TiO2 plasmonic photocatalysts

The activity of Au nanoparticle-loaded P25 TiO2 (Au/P25) plasmonic photocatalysts, evaluated by the oxidative decomposition of formic acid in water under visible light irradiation, was enhanced up to 3 times by simply mixing Au/P25 with photocatalytically inactive h-BN nanosheets as a result of electron transfer from photoexcited Au/TiO2 to the h-BN nanosheets and retardation of the charge recombination.

Unprecedentedly enhanced solar photocatalytic activity of a layered titanate simply integrated with TiO2 nanoparticles

We report a simple, low-cost methodology for unprecedentedly enhancing the photocatalytic activity of layered inorganic semiconductors. A layered titanate with a lepidocrocite-type structure scarcely showed photocatalytic activity for a test reaction, the oxidative decomposition of formic acid in water into CO2, under simulated solar light, but it showed highly enhanced photocatalytic activity upon mixing with a much smaller amount (approximately 10 wt%) of commercially available TiO2 nanoparticles (P25) in water. The photocatalytic activity of the mixture was approximately 5 times that of P25, a benchmark photocatalyst. From various analyses, the enhancement resulted from the transfer of photoexcited electrons from the layered titanate to P25 at their particle interfaces and retardation of charge recombination. When applied to a photocatalyst for H2 production from water containing methanol under simulated solar light, the layered titanate/P25 mixture showed considerably enhanced activity and the apparent quantum yield was 23% (at 320 nm). By replacing P25 with Pt co-catalyst-loaded P25, the apparent quantum yield of the mixture increased from 23 to 73%, although an extremely small amount (below 0.06%) of Pt was used in the system.

Room-Temperature Rutile TiO2 Nanoparticle Formation on Protonated Layered Titanate for High-Performance Heterojunction Creation

We report a methodology for creating protonated layered titanate-rutile heterojunctions on the outer particle surface of protonated layered titanate by treating layered potassium titanate (K0.8Ti1.73Li0.27O4) with dilute HCl and then drying it at room temperature under reduced pressure. After Pt co-catalyst loading, this protonated layered titanate/rutile composite with heterojunctions showed higher photocatalytic H2 evolution activity from water under simulated solar light compared to that of Pt-loaded P25, the standard photocatalyst for this reaction. The high photocatalytic activity was ascribable to enhanced photocatalytic activity of the protonated layered titanate based on an efficient charge separation at the protonated layered titanate-rutile heterojunction in addition to the sensitization effects of rutile, which absorbs light with longer wavelengths compared to those of protonated layered titanate.