Kenichirou Suzuki

Hydrogen generation using sodium borohydride solution and metal catalyst coated on metal oxide

Abstract Sodium borohydride (NaBH4) reacted slowly with water to liberate 4 mol of hydrogen/mol of the compound at room temperature. Hydrogen generation was accelerated by applying metal–metal oxide catalysts such as Pt–TiO2, Pt–CoO and Pt–LiCoO2. As the metal crystallites size decreased and the amount increased, the hydrogen generation rate increased. It was indicated that the hydrogen generation rates using Pt and LiCoO2 were high compared with those using other metal and metal oxide, respectively. It seemed that a key finding was that use of the supercritical CO2 method produced a superior catalyst. Borohydride ion was stabilized in alkaline solution containing at least 5% by weight of NaOH. Alkaline stabilized solution of NaBH4 can be applied as a hydrogen source. We found that Pt–LiCoO2 worked as an excellent catalyst for releasing hydrogen from the stabilized NaBH4 solution.

Monodisperse, bimodal mesoporous ceria catalysts and adsorbents for air purification

We report for the first time a novel bimodal mesoporous crystalline ceria with nanometer-sized, pseudo-spherical, monodisperse particles. This mesoporous ceria was prepared using block-copolymer templates and non-aqueous solvent. The surface areas, mesopore structure and thermal stabilities of the final product are found to depend on the gel composition. The material shows very high sorption and catalytic properties for the elimination of acetaldehyde compared to semicrystalline mesoporous ceria and non-porous crystalline ceria materials. The material also showed acetaldehyde elimination ability twice as high as that of conventional materials.

Mesoporous Ferrihydrite‐Based Iron Oxide Nanoparticles as Highly Promising Materials for Ozone Removal

Gaseous ozone (O3) in the troposphere is considered to be one of the most harmful air pollutants in view of its high reactivity and immediate action to the surroundings, which causes both shortand long-term adverse health effect and also disrupts plant growth. Materials explored for eliminating O3 in several applications include activated carbon or carbon-promoted oxide materials, noble-metal-supported catalysts, and various transition-metal oxides. These materials have diverse drawbacks: they must often be deposited on high-surface-area metal oxides or mixed with organic additives to enhance their performance, they use expensive metal components, they are not very environmentally friendly, and they are not flexible enough to use as a common choice in a wide range of sectors. Herein, we report for the first time that the two-line ferrihydrite (2LFh) with accessible mesopores can be used as a potential candidate for O3 removal. The following aspects prompted us to consider mesoporous 2LFh (M2LFh) a judicial choice for O3 removal: 1) it possesses high surface area and, being in the ferrihydrite (Fh) phase, a much higher percentage of iron sites are at or near the surface than in the bulk; 2) with accessible mesopores, Fh nanoparticles have the potential for high adsorption owing to an increased rate of mass transfer to the reactive iron sites, such as we recently reported for their high efficiency in rapidly removing organic contaminants in the air; and 3) as an oxyhydroxide of iron, Fh is environmentally friendly and can be applied in various sectors. We also show herein that the presence of Fh nanoparticles in disordered mesostructured iron oxide has a significant effect on the bulk and surface structure of the material and on the activity. Our findings can contribute toward designing Fh-based materials as new potential catalysts for rapid removal of O3 and its decomposition. M2LFh was prepared according to a reported procedure by assembly of Fh nanoparticles in 1-propanol in the presence of polyoxyethylene (20) cetyl ether template. Additionally, a mesostructured semicrystalline iron oxide composed of amorphous Fh nanoparticles and crystalline g-Fe2O3 phase (MSIO) and a crystalline iron oxide with no welldefined mesopores (CIO) were prepared for comparison. MSIO was prepared through a sol–gel process in which iron nitrate, oleic acid, a triblock polymer template (F127), and 1propanol were mixed, with subsequent ageing and calcination. CIO was prepared by assembly of iron oxyhydroxide in a water/ethylene glycol mixture in the presence of cetyltrimethylammonium bromide. Details of MSIO and CIO synthesis are given in the Supporting Information. The wide-angle XRD pattern of M2LFh (Figure 1a,A) shows two broad reflections of the 2LFh phase. Although the amorphous Fh-phase reflections in the XRD pattern of MSIO

The first application of fullerene polymer-like materials, C60Pdn, as gas adsorbents

C60Pdn polymer-like materials were prepared and reacted with toluene, one of the harmful gases. Toluene was successfully adsorbed on C60Pdn at ambient temperature without additional energy sources. This adsorptivity was retained even at low concentration (1000 ppb), which is close to the actual toluene concentration in the environment. The strong adsorption of toluene molecules toward C60Pdn was confirmed by IR, TG-IR, and cyclic voltammetric analyses. The π-electrons of toluene are believed to adsorb on partially positive Pd atoms of C60Pdn, and theoretical studies have suggested that π-electrons of C60 and toluene overlap through the d-electron orbitals of the Pd atom, not just physical adsorption. This result should open the route to fullerene materials as adsorbents for harmful gases.

Novel Mesoporous Cerium Oxide for Air Purification Material

Mesoporous ceria structures with different porosities were prepared using block-copolymer templates and non-aqueous solvents. The surface areas, mesopore ordering and thermal stabilities of the final product are found to vary with the gel composition. Spherical cerium oxide with disordered wormholelike mesoporosity, high surface area and high thermal stability could be prepared using propanol solvent. Such materials are promising for application in air-purification materials. Using mixed propanol, ethylene glycol medium hexagonally ordered mesoporous ceria was obtained but the material had poor thermal stability.

Crystallization of stable mesoporous zirconia and ceria-zirconia

Crystallization of Mesoporous zirconia and ceria-zirconia structures were realized using a long-chain amine template. By controlled heating of the synthesis gel it was possible to prepare well-crystalline mesoporous strctures for these materials. The surface areas, mesopore ordering and thermal stabilities of the final product is dependent on the composition, ageing and heating condition for the precursor gel.