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Sreethawong T.,Baan Klangmuang Luzern | Yoshikawa S.,Kyoto University
Materials Research Bulletin | Year: 2012

In this work, the photocatalytic water splitting under visible light irradiation for hydrogen production was investigated by using Eosin Y-sensitized Pt-loaded mesoporous-assembled TiO 2-ZrO 2 mixed oxide nanocrystal photocatalysts. The mesoporous-assembled TiO 2-ZrO 2 mixed oxide with the TiO 2-to-ZrO 2 molar ratio of 95:5 (i.e. 0.95TiO 2-0.05ZrO 2) was synthesized by using a sol-gel process with the aid of a structure-directing surfactant. The Pt loading was comparatively performed via two different effective methods: single-step sol-gel (SSSG) and photochemical deposition (PCD). The synthesized photocatalysts were methodically characterized by N 2 adsorption-desorption, XRD, UV-visible spectroscopy, SEM-EDX, TEM-EDX, TPR, and H 2 chemisorption analyses. The results revealed that the Pt loading by the PCD method greatly enhanced the photocatalytic hydrogen production activity of the synthesized mesoporous-assembled 0.95TiO 2-0. 05ZrO 2 mixed oxide photocatalyst more than that by the SSSG method. The optimum Pt loading by the PCD method was experimentally observed at 0.5 wt.%, which was well associated with the maximum Pt dispersion. In addition, the PCD conditions, i.e. UV light irradiation time and UV light intensity, were investigated and optimized to be 2 h and 44 W, respectively. © 2012 Elsevier Ltd. All rights reserved. Source


Sreethawong T.,Baan Klangmuang Luzern | Ngamsinlapasathian S.,Kyoto University | Yoshikawa S.,Kyoto University
Materials Research Bulletin | Year: 2012

In this work, the mesoporous-assembled TiO 2 nanocrystals were successfully synthesized by a modified sol-gel process under mild conditions with the aid of glycerol, which is a main by-product from biodiesel production via the transesterification of vegetable oils. The synthesized TiO 2 nanocrystals were characterized by various techniques, i.e. N 2 adsorption-desorption, SEM, high resolution TEM, and XRD. The characterization results clearly showed that the glycerol could behave as an efficient mesopore-controlling agent, which induced the mesoporous-assembled characteristic of the synthesized TiO 2 nanocrystals with very narrow pore size distribution. The synthesized mesoporous-assembled TiO 2 nanocrystals were applied for hydrogen production from the photocatalytic water splitting. The photocatalytic activity results revealed that the synthesized mesoporous-assembled TiO 2 nanocrystals possessed much higher hydrogen production activity than the commercially available P-25 TiO 2 and ST-01 TiO 2 powders. © 2011 Elsevier Ltd. All rights reserved. Source


In this work, the monometallic Pt and bimetallic Pt-Au nanoparticles-loaded mesoporous-assembled TiO2-SiO2 mixed oxide nanocrystal photocatalysts were investigated for hydrogen production from the photocatalytic Eosin Y-sensitized water splitting under visible light irradiation. A sol-gel process with the aid of a structure-directing surfactant was employed to synthesize the mesoporous-assembled TiO2-SiO2 mixed oxide with the TiO2-to-SiO2 molar ratio of 97:3 (i.e. 0.97TiO2-0.03SiO2), which was used as the base semiconductor photocatalyst. The Pt and/or Au loadings on the 0.97TiO2-0.03SiO2 mixed oxide photocatalyst were achieved via a photochemical deposition method. The synthesized photocatalysts were systematically characterized by N2 adsorption-desorption, XRD, UV-visible spectroscopy, SEM-EDX, TEM-EDX, and H2 chemisorption analyses. The photocatalytic hydrogen production activity results revealed that the optimum monometallic Pt loading for a maximum photocatalytic activity was 1.25wt.%, which corresponded very well to its maximum Pt dispersion. The increase in the Pt loading to a higher value of 1.5wt.% unfavorably decreased the photocatalytic activity; however, the dilution of Pt by Au to attain the bimetallic 0.75wt.% Pt-0.75wt.% Au loading (with high total metal loading of 1.5wt.%) was found to preserve the photocatalytic activity at an acceptably high level. © 2012 Elsevier B.V. Source


Sreethawong T.,Baan Klangmuang Luzern | Ngamsinlapasathian S.,Kyoto University | Yoshikawa S.,Kyoto University
Materials Letters | Year: 2012

A modified sol-gel process with the aid of a structure-directing surfactant was employed to synthesize crystalline mesoporous Nb 2O 5 nanoparticles under mild conditions. The XRD result revealed that the synthesized Nb 2O 5 nanoparticles exhibit a single crystalline orthorhombic phase without any impurities. The N 2 adsorption-desorption isotherm, pore size distribution, SEM, and high resolution TEM results clearly indicated that the synthesized Nb 2O 5 nanoparticles possess monomodal pore size distribution in the mesoporous range with uniform porous structure. The synthesized mesoporous Nb 2O 5 has a specific surface area of 97.5 m 2/g, a mean mesopore diameter of 12.2 nm, and a total pore volume of 0.41 cm 3/g. Additionally, the UV-visible spectrum result suggested that the synthesized mesoporous Nb 2O 5 is a potential UV light-absorbing material. © 2012 Elsevier B.V. All rights reserved. Source


Sreethawong T.,Baan Klangmuang Luzern | Ngamsinlapasathian S.,Kyoto University | Yoshikawa S.,Kyoto University
Chemical Engineering Journal | Year: 2012

In this work, the mesoporous-assembled TiO2-NiO mixed oxide nanocrystals were successfully synthesized by a sol-gel process with the aid of a structure-directing surfactant under mild conditions. The photocatalytic activity of the synthesized mixed oxide nanocrystals for degradation of Methyl Orange (MO) azo dye used as a model wastewater contaminant was investigated under UV light irradiation. The synthesized mixed oxide nanocrystals were systematically characterized by TG-DTA, N2 adsorption-desorption analysis, SEM-EDX, XRD, and UV-visible spectroscopy. The photocatalytic activity results showed that the incorporation of NiO phase with a suitable content into the TiO2-NiO mixed oxide increased the photocatalytic MO degradation efficiency. It was found that the mesoporous-assembled Ti75-Ni25 mixed oxide nanocrystal (with 75mol % TiO2 and 25mol % NiO) provided a maximum MO degradation efficiency as compared to the other investigated nanocrystals as well as the commercial P-25 TiO2 powder. The induced n-p junction at the interfacial contact between the TiO2 and NiO phases in the Ti75-Ni25 mixed oxide nanocrystal is supposed to efficiently prevent the electron-hole recombination upon the UV light excitation and consequently enhance its photocatalytic degradation activity. © 2012 Elsevier B.V. Source

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