Masaru Harada

Application of ion beam techniques for preparation of metal ion-implanted TiO2 thin film photocatalyst available under visible light irradiation: metal ion-implantation and ionized cluster beam method.

Transparent TiO2 thin film photocatalysts have been prepared on silica glass plate by an Ionized Cluster Beam (ICB) method. In order to improve the electronic properties of these photocatalysts, transition metal ions (V+, Cr+, Mn+, Fe+) were implanted into the TiO2 thin films at high energy acceleration using an advanced metal ion-implantation technique. The combination of these ion beam techniques can allow us to prepare the TiO2 thin film photocatalysts which can work effectively under visible light (lambda>450 nm) and/or solar light irradiation. The investigation using XAFS and ab initio molecular calculation suggests that the substitution of octahedrally coordinated Ti ions in TiO2 lattice with implanted metal ions is important to modify TiO2 to be able to adsorb visible light and operate under visible light irradiation.

Preparation of efficient titanium oxide photocatalysts by an ionized cluster beam (ICB) method and their photocatalytic reactivities for the purification of water

Abstract Using an ionized cluster beam (ICB) method, titanium oxide photocatalysts were prepared on porous Vycor silica glass (PVG) and activated carbon fibers (ACF), and their photocatalytic reactivities for the degradation of 2-propanol diluted in water was investigated. Characterizations of these catalysts by means of SEM, XAFS, XRD, XPS and UV–Vis absorption techniques showed that the titanium oxide in transparent thin films could be formed on PVG and titanium oxide clusters could be deposited on the ACF. UV irradiation of these catalysts in a diluted aqueous solution of 2-propanol or 1,2-dichloroethane led to the efficient decomposition of these reactants into CO 2 , H 2 O and HCl. The titanium oxide catalysts prepared on these porous materials exhibited higher photocatalytic reactivities than TiO 2 powder and titanium oxide catalysts prepared by a conventional impregnation method. The present results have clearly shown that the ICB method is useful in the preparation of titanium oxide photocatalysts combined with porous supports such as PVG and ACF.

Preparation and characterizations of Fe- or Ni-substituted titania nanosheets as photocatalysts

Abstract Fe- or Ni-substituted titania nanosheets have been synthesized by chemically exfoliating precursor layered titanates into colloidal single sheets. Obtained nanosheets were self-assembled via consecutive adsorption with polycations to produce multilayer ultrathin films, which exhibit photocatalytic properties. In the case of Fe system, UV absorption band was widened towards the visible light region in comparison with that of titania nanosheets of Ti 0.9 O 2 .

Preparation of Titanium Oxide Photocatalysts Loaded On Activated Carbon and Their Photocatalytic Reactivity for the Degradation of 2-Propanol Diluted in Water

Titanium oxide catalysts loaded on activated carbon (AC) as an adsorbent support were prepared and used as photocatalysts. The photocatalytic reactivity of these catalysts was investigated for the liquid-phase oxidation of 2-propanol diluted in water, and it was found that photocatalysts having the high adsorption ability for activated carbon and the high crystallinity of the anatase TiO 2 phase exhibited efficient photocatalytic reactivity. However, the presence of Cl ions on the activated carbon worked to promote the aggregation of titanium oxide species, and they also promote the formation of a rutile TiO 2 phase which was not preferable for the preparation of efficient TiO 2 /AC photocatalysts.

Application of ion beams for preparation of TiO2 thin film photocatalysts operatable under visible light irradiation: Ion-assisted deposition and metal ion-implantation

The visible light sensitive TiO2 thin film photocatalysts can be developed by the application of ion beam techniques, i.e. the combination of an ion-assisted deposition (IAD) method and a metal ion-implantation. The transparent TiO2 thin film photocatalysts have been prepared on silica glass plate by the IAD method. Then the transition metal ions (V+) were implanted into the TiO2 thin films at high energy acceleration using a metal ion-implantation technique to improve the electronic properties of the TiO2 thin film to be able to work effectively as photocatalysts under visible light (λ>450 nm) and/or solar light irradiation. The investigation using X-ray absorption fine structure analysis and ab initio molecular calculation suggest that the substitution of octahedrally coordinated Ti ions in TiO2 lattice with implanted metal ions (V+) is important to modify TiO2 to be able to adsorb visible light and operate under visible light irradiation.

Characterization of Ti/Si binary oxides prepared by the sol-gel method and their photocatalytic properties: The hydrogenation and hydrogenolysis of CH3CCH with H2O

Titanium-silicon (Ti/Si) binary oxides having different Ti content were prepared by the sol-gel method and utilized as photocatalysts for the hydrogenation and hydrogenolysis of CH2CCH with H2O. The photocatalytic reactivity and selectivity of these catalysts were investigated as a function of the Ti content and it was found that the hydrogenolysis reaction (C2H6 formation) was predominant in regions of low Ti content, while the hydrogenation reaction (C3H6 formation) proceeded in regions of high Ti content. The in situ photoluminescence, diffuse reflectance absorption, FT-IR, XAFS (XANES and EXAFS), and XPS spectroscopic investigations of these Ti/Si binary oxides indicated that the titanium oxide species are highly dispersed in the SiO2 matrices and exist in a tetrahedral coordination exhibiting a characteristic photoluminescence spectrum. The charge transfer excited state of the tetrahedrally coordinated titanium oxide species plays a significant role in the efficient photoreaction with a high selectivity for the hydrogenolysis of CH3CCH to produces mainly C2H6 and CH4, while the catalysts involving the aggregated octahedrally coordinated titanium oxide species show a high selectivity for the hydrogenation of CH3CCH to produce C3H6, being similar to reactions of the powdered TiO2 catalysts. The good parallel relationship between the yield of the photoluminescence and the specific photocatalytic reactivity of the Ti/Si binary oxides as a function of the Ti content clearly indicates that the high photocatalytic reactivity of the Ti/Si binary oxides having low Ti content is associated with the high reactivity of the charge transfer excited state of the isolated titanium oxide species in tetrahedral coordination, [Ti3+-O−]*.

Preparation of Titanium Oxide Photocatalysts Loaded on Activated Carbon by an Ionized Cluster Beam Method and Their Photocatalytic Reactivities for the Degradation of 2-Propanol Diluted in Water

— 500 without causing any damages to the supports. Characterizations of these catalysts by means of SEM. XAFS and XRD techniques showed that titanium oxide clusters are formed on the supports in an anatase structure. UV irradiation of these catalysts in a diluted aqueous solution of 2-propanol led to the formation of acetone and CO,, indicating that the titanium oxide clusters exhibit efficient photocatalytic reactivity. Thus, the present results have clearly demonstrated that the ICB method is useful in the development of a combination system of titanium oxide photocatalysts and porous supports such as activated carbons without calcination treatment at high temperatures.

Preparation of hollandite-type KxGaxSn8-xO16 thin film and NO adsorption behavior

Abstract Thin films of hollandite-type K x Ga x Sn 8− x O 16 (KGSO) were fabricated on YSZ substrate by spin-coating method. Those are colorless and transparent, and about 100–150 nm thick at minimum, consisting of KGSO primary particles with about 20 nm in average size. The adsorption behavior of NO on the thin film was examined by diffuse reflectance infrared fourier transform spectroscopy and temperature programmed desorption method. The sample was preheated at 973 K in a mixture gas of N 2 and O 2 prior to NO adsorption. As the oxygen ratio in the mixture gas increased up to 40%, absorption bands appeared and got stronger an around 1400 cm −1 , and the amount of desorption in the range from 650 to 850 K increased. Those bands were assigned to NO 2 species in the chelating and nitrito form, respectively, referring to the literature about NO on La 2 O 3 . The amount of desorption was equal to the number of tunnel end face per unit cell. It was found that the coexistence of oxygen remarkably improves the adsorption ability of NO on KGSO thin films.

Preparation of efficient titanium oxide photocatalysts by an ionized cluster beam method and their application for the degradation of propanol diluted in water

Titanium oxide catalysts were prepared on porous Vycor glass (PVG) and activated carbon fibers (ACF) using an ionized cluster beam (ICB) method and their photocatalytic reactivity for the degradation of 2-propanol diluted in water was investigated. Characterizations of these catalysts by means of SEM, XAFS and XRD techniques showed that titanium oxide thin films and titanium oxide clusters could be formed on PVG and ACF, respectively, mainly in an anatase structure. UV irradiation of these catalysts in a diluted aqueous solution of 2-propanol led to the formation of acetone and CO 2 , demonstrating that the titanium oxide species prepared on these porous materials exhibited efficient photocatalytic reactivity. The present results have clearly shown the ICB method to be useful in the development of titanium oxide photocatalysts combined with porous supports such as PVG and ACF without any calcination pretreatment at high temperatures.

Photoinduced hydrophilicity and photocatalytic decomposition of endocrine-disrupting chemical pentachlorophenol on hollandite

Surface properties and photocatalytic oxidation reactions on the hollandite-type compound K 2 Ga 2 Sn 6 O 16 (KGSO) were examined for photoinduced hydrophilicity and oxidative decomposition of an endocrine-disrupting chemical, pentachlorophenol (C 6 Cl 5 OH, PCP), under ultraviolet (UV) illumination. The thin films and mesoporous powders of hollandite were used for examination of surface properties and photocatalysis, respectively. The photoinduced surface property was examined by measurement of the contact angle of water, ortho -chlorophenol ( o -C 6 H 4 ClOH), and toluene on the surface of KGSO. The contact angle of H 2 O and o -C 6 H 4 ClOH decreased to 0° under UV illumination. The toluene showed little change in contact angle under UV irradiation. It is concluded that the surface of KGSO shows photoinduced hydrophilicity for H 2 O and aromatic compounds with hydroxyl groups (−OH). In addition, KGSO clearly showed a photo-oxidative decomposition of PCP under weak UV illumination at room temperature. The decomposition speed of C 6 Cl 5 OH on KGSO was much faster than that on previous reported nano-sized SnO 2 photocatalysts. It is expected that photo-oxidative decomposition of aromatic compound will be controlled by a combination of optimum composition of the hollandite phase and control of the morphology of the hollandite particles. This suggests that hollandite would be a promising photocatalyst for decomposition of aromatic compounds in endocrine-disrupting chemicals.