Satoshi Ohshiro

Visible-light-responsive photocatalytic reaction on tetrahedrally-coordinated chromium oxide moieties loaded on ZSM-5 zeolites and HMS mesoporous silica: partial oxidation of propane

Chromium oxide (Cr-oxide) moieties loaded on ZSM-5 zeolites and HMS mesoporous silica molecular sieves were prepared by an impregnation method and characterized by various spectroscopic methods (XRD, XAFS, UV-Vis, photoluminescence) and their photocatalytic reactivities for partial oxidation of propane under visible light irradiation were investigated. The local structure of Cr-oxide species depended to a large extent on the zeolite types and Si/A1 ratios of zeolites. Tetrahedrally-coordinated isolated Cr-oxide moieties can be loaded on HMS and ZSM-5 having the higher Si/A1 ratios. On these catalysts, in the presence of propane and O2, a partial oxidation proceeded under visible light irradiation to produce acetone with high selectivity. The charge-transfer excited state of the tetrahedral Cr-oxide moieties plays a significant role in the selective photocatalytic reactions under visible light irradiation.

Visible-light-sensitive photocatalytic reaction on chromium-containing mesoporous silica: selective partial oxidation of propane with molecular oxygen

The photocatalytic reactivities of chromium-containing mesoporous silica molecular sieves (Cr-HMS) under visible light irradiation have been investigated. Cr-HMS involves tetrahedral chromium oxide (Cr-oxide) moieties which are highly dispersed and incorporated in the framework of molecular sieve with two terminal Cr=O groups. In the presence of propane with molecular oxygen, a partial oxidation proceeded under visible light irradiation to produce acetone and acrolein, with high selectivity, while a complete oxidation proceeded under UV light irradiation mainly to produce CO2. The charge-transfer excited state of the tetrahedral Cr-oxide moieties plays a significant role in the photocatalytic reactions.

Design of visible light sensitive (Cr, Ti)-containing mesoporous silica photocatalyst using a photo-assisted deposition (PAD) method

It is vital to develop a visible light sensitive photocatalyst. In this study, (Cr,Ti)-binary oxide containing mesoporous silica (Cr/Ti-HMS) photocatalyst was prepared by an application of a photo-assisted deposition (PAD) technique and characterized by XAFS and photoluminescence studies. Using the PAD method, the tetrahedrally coordinated Cr-oxide moieties can be anchored on Ti-HMS forming the direct interaction between Cr-oxide and Ti-oxide moieties. The Cr/Ti-HMS exhibited the high efficiency and selectivity in the photoepoxidation of propene with O2 under visible light irradiation. The charge transfer excited state of the Cr-oxide moieties anchored on Ti-oxide moieties play a significant role in photocatalytic reactions under visible light irradiation.

XAFS Study on the VisibleLight Sensitive CrContaining Zeolite Photocatalyst Mesoporous CrHMS Molecular Sieves

The Cr-containing mesoporous molecular sieves (Cr-HMS) operated as efficient photocatalyst for the decomposition of NO into N2 and O2 even under visible light irradiation (λ > 450 nm). This photocatalyst exhibited a sharp and intense pre-edge peak in the XANES region which was characteristic of Cr-oxide species in tetrahedral coordination. In the Fourier transform of EXAFS spectrum, only a single peak due to the neighboring oxygen atoms was observed and the curve-fitting analysis indicated that 4-coordinated Cr-oxide moieties having two terminal Cr=O bonds were present. The results obtained with XAFS analysis as well as the analyses with UV-VIS absorption and photoluminescence measurements indicate that the charge transfer excited state of the tetrahedrally coordinated Cr-oxide moieties play a significant role in the photocatalytic reaction under visible light irradiation.