Showing papers by "Masaya Matsuoka published in 2013"

Recent advances in visible-light-responsive photocatalysts for hydrogen production and solar energy conversion – from semiconducting TiO2 to MOF/PCP photocatalysts

Abstract: The present perspective describes recent advances in visible-light-responsive photocatalysts intended to develop novel and efficient solar energy conversion technologies, including water splitting and photofuel cells Water splitting is recognized as one of the most promising techniques to convert solar energy as a clean and abundant energy resource into chemical energy in the form of hydrogen In recent years, increasing concern is directed to not only the development of new photocatalytic materials but also the importance of technologies to produce hydrogen and oxygen separately Photofuel cells can convert solar energy into electrical energy by decomposing bio-related compounds and livestock waste as fuels The advances of photocatalysts enabling these solar energy conversion technologies have been going on since the discovery of semiconducting titanium dioxide materials and have extended to organic–inorganic hybrid materials, such as metal–organic frameworks and porous coordination polymers (MOF/PCP)

Application of an amino-functionalised metal–organic framework: an approach to a one-pot acid–base reaction

Abstract: The amino-functionalised metal–organic framework, MIL-101(Al)-NH2, has been synthesized by using a solvothermal method and employed as a bifunctional acid–base catalyst for a one-pot, sequential deacetalization–Knoevenagel condensation reaction. In preliminary studies, the abilities of MIL-101(Al)-NH2 to serve as an acid and base catalyst were explored separately by two typical acid- and base-catalysed reaction, that is, deacetalization of benzaldehyde dimethylacetal and Knoevenagel condensation of benzaldehyde with malononitrile. MIL-101(Al)-NH2 was found to catalyse each of these reactions with high efficiency. MIL-101(Al)-NH2 was then employed as a catalyst for the one-pot sequential deacetalization–Knoevenagel condensation reaction between benzaldehyde dimethylacetal and malononitrile. Benzylidenemalononitrile as the final product was successfully generated with a high yield via benzaldehyde over MIL-101(Al)-NH2. In addition, the catalytic ability of MIL-101(Al)-NH2 was demonstrated to be superior to those of conventional heterogeneous, homogeneous as well as other functionalised metal–organic framework catalysts. Finally, the results show that MIL-101(Al)-NH2 can be reused as a catalyst for this process without significant loss of its activity.

Effect of pore sizes on catalytic activities of arenetricarbonyl metal complexes constructed within Zr-based MOFs

Abstract: Arenetricarbonyl metal complexes ([–phM(CO)3–] and [–biphM(CO)3–]; ph = phenylene, biph = biphenylene, M = Mo, Cr) constructed within Zr-based MOFs act as highly active and selective catalysts for epoxidation of cyclooctene. Catalytic activities of these complexes are enhanced with increasing the pore sizes of Zr-based MOFs.

Development of Ruthenium-loaded Alkaline-earth Titanates as Catalysts for Ammonia Synthesis

Abstract: Ru-loaded alkaline-earth titanates show efficient catalytic activities for ammonia synthesis because of the electronic promotion effects induced by alkaline-earth elements and the low acidity of th...

Separate-type Pt-free photofuel cell based on a visible light-responsive TiO2 photoanode: Effect of hydrofluoric acid treatment of the photoanode

Abstract: The present study deals with the effect of a hydrofluoric acid (HF) treatment of visible light-responsive TiO 2 (Vis-TiO 2 ) thin film photocatalysts on their photoelectrochemical performances. The Vis-TiO 2 thin film photocatalysts have been prepared on Ti metal substrates by a magnetron sputtering deposition method and then treated by an HF solution. The HF treatment of Vis-TiO 2 thin film photocatalysts leads to the dramatic enhancement of their photoelectrochemical performances under UV light and visible light irradiation. Moreover, separate-type Pt-free photofuel cells (SPFCs) constructed using the Vis-TiO 2 thin films as photoanodes can generate electricity under light irradiation and simultaneously decompose methanol. The SPFC based on the Vis-TiO 2 thin film photoanode etched by HF solution shows the enhanced cell performances with two times higher short-circuit current density and higher energy conversion efficiency than that based on the untreated Vis-TiO 2 thin film photoanode. In addition to the increase of surface area and surface roughness, the enhanced conductivity by HF treatment, which is confirmed by Mott–Schottky analyses, is found to be responsible for improvement of cell performances of the SPFC.

Development of dye-sensitized solar cells based on visible-light-responsive TiO2 thin films with a unique columnar structure

Abstract: A visible-light-responsive TiO2 thin film (Vis-TiO2), possessing a unique columnar structure oriented perpendicular to the substrate, has been prepared by using a radio-frequency magnetron sputtering deposition method. The unique TiO2 thin film was used as a key component of N719 dye-sensitized solar cells (DSSCs). The rough morphology caused by the columnar structure leads to enhanced photovoltaic performances of these DSSCs as a consequence of increased amounts of adsorbed dyes and facilitated diffusion of the electrolyte into Vis-TiO2 film. Additionally, photovoltaic performances of the DSSCs were found to depend strongly on the thickness of the Vis-TiO2 film, which can be readily controlled by adjusting the sputtering time conducted for deposition. Consequently, a solar-to-electric energy conversion efficiency of 2.6 % under AM 1.5 illumination was observed for an optimally performing DSSC that has a Vis-TiO2 film thickness of 6.9 μm, prepared by employing a sputtering time of 700 min.

Effect of the sputtering parameters on the physical properties and photocatalytic reactivity of TiO2 thin films prepared by an RF magnetron sputtering deposition method

Abstract: Visible light-responsive TiO2 (Vis-TiO2) thin films were successfully developed by applying a radio-frequency magnetron sputtering deposition method by controlling various sputtering parameters such as the substrate temperature, Ar gas pressure, and the target-to-substrate distance. UV–Vis, XRD and SEM investigations revealed that optical property, the crystal structure, and photocatalytic activity of Vis-TiO2 are strongly affected by the sputtering parameters during the deposition step. Vis-TiO2 was found to act as an efficient photocatalyst for the H2 and O2 evolution from water under visible light irradiation (λ ≥ 420 nm). SIMS investigations have revealed that a slight decrease in the O/Ti ratio of the TiO2 thin films plays an important role in the modification of the electronic properties of Vis-TiO2 thin films, enabling them to absorb visible light.

Enhanced photoelectrochemical properties of visible light-responsive TiO2 photoanode for separate-type Pt-free photofuel cells by Rh3+ addition

Abstract: Visible light-responsive TiO2 (Vis-TiO2) electrode has been applied for the Pt-free separate-type photofuel cell (SPFC) where two different electrolytes containing various biomass derivatives and a I3 −/I− redox solution were employed for the anode and cathode sides, respectively. This new SPFC exhibits good photoelectrochemical performance under simulated solar-light irradiation. It was found that the Rh3+ loading on Vis-TiO2 electrode enhanced the photoelectrochemical performance of the SPFC through the increase in the visible light absorption as well as the increase in the electron conductivity of Vis-TiO2 electrode.