Tokyo University of Science

About: Tokyo University of Science is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Thin film & Enantioselective synthesis. The organization has 15800 authors who have published 24147 publications receiving 438081 citations. The organization is also known as: Tōkyō Rika Daigaku & Science University of Tokyo.

Water Splitting into H2 and O2 on Alkali Tantalate Photocatalysts ATaO3 (A = Li, Na, and K)

Abstract: Alkali tantalate ATaO3 (A = Li, Na, and K) photocatalysts with perovskite-like structure showed activities for water splitting into H2 and O2 under UV irradiation. When the alkali tantalates were prepared in the presence of excess alkali, their activities were increased by 1 to 2 orders of magnitude. Scanning electron microscopy and photoluminescence measurements indicated that the excess alkali in the preparation increased the crystal size of NaTaO3 formed and prevented formation of alkali defects in NaTaO3 powder by volatilization, resulting in an increase in the photocatalytic activity. A LiTaO3 photocatalyst showed the highest activity among the naked alkali tantalate photocatalysts prepared in the presence of excess alkali. On the other hand, the activity of a NaTaO3 photocatalyst was increased by 1 order of magnitude when a NiO cocatalyst was loaded. The NiO(0.05 wt %)/NaTaO3 photocatalyst produced H2 and O2 from pure water with rates of 3.39 and 1.58 mmol h-1, respectively. The apparent quantum yie...

Preparation of PAMAM− and PPI−Metal (Silver, Platinum, and Palladium) Nanocomposites and Their Catalytic Activities for Reduction of 4-Nitrophenol

Abstract: Dendrimer-metal (silver, platinum, and palladium) nanocomposites are prepared in aqueous solutions containing poly(amidoamine) (PAMAM) dendrimers with surface amino groups (generations 3, 4, and 5) or poly(propyleneimine) (PPI) dendrimers with surface amino groups (generations 2, 3, and 4) The particle sizes of the metal nanoparticles obtained are almost independent of the generation as well as the concentration of the dendrimer for both the PAMAM and the PPI dendrimers; the average sizes of silver, platinum, and palladium nanoparticles are 56-75, 12-16, and 16-20 nm, respectively It is suggested that the dendrimer-metal nanocomposites are formed by adsorbing the dendrimers on the metal nanoparticles Studies of the reduction reaction of 4-nitrophenol by these nanocomposites show that the rate constants are very similar between PAMAM and PPI dendrimer-silver nanocomposites, whereas the rate constants for the PPI dendrimer-platinum and -palladium nanocomposites are greater than those for the corresponding PAMAM dendrimer nanocomposites In addition, it is found that the rate constants for the reduction of 4-nitrophenol involving all the dendrimer-metal nanocomposites decrease with an increase in the dendrimer concentrations, and the catalytic activity of dendrimer-palladium nanocomposites is highest

Study on the Reversible Electrode Reaction of Na1–xNi0.5Mn0.5O2 for a Rechargeable Sodium-Ion Battery

Abstract: Layered NaNi0.5Mn0.5O2 (space group: R3m), having an O3-type (α-NaFeO2 type) structure according to the Delmas’ notation, is prepared by a solid-state method. The electrochemical reactivity of NaNi0.5Mn0.5O2 is examined in an aprotic sodium cell at room temperature. The NaNi0.5Mn0.5O2 electrodes can deliver ca. 105–125 mAh g–1 at rates of 240–4.8 mA g–1 in the voltage range of 2.2–3.8 V and show 75% of the initial reversible capacity after 50 charge/discharge cycling tests. In the voltage range of 2.2–4.5 V, a higher reversible capacity of 185 mAh g–1 is achieved; however, its reversibility is insufficient because of the significant expansion of interslab space by charging to 4.5 V versus sodium. The reversbility is improved by adding fluoroethylene carbonate into the electrolyte solution. The structural transition mechanism of Na1–xNi0.5Mn0.5O2 is also examined by an ex situ X-ray diffraction method combined with X-ray absorption spectroscopy (XAS). The staking sequence of the [Ni0.5Mn0.5]O2 slabs chang...

Fluorinated Ethylene Carbonate as Electrolyte Additive for Rechargeable Na Batteries

Abstract: Fluoroethylene carbonate is an efficient electrolyte additive to improve the reversibility of electrochemical sodium insertion for hard-carbon and NaNi1/2Mn1/2O2 electrodes in aprotic Na cells. The additive is also capable of the electrochemical deposition/dissolution of metallic Na with higher reversibility because of improved passivation and suppression of side reactions between Na metal and propylene carbonate solution containing Na salts.