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This study is the first report on liquid water and ice imaging conducted at a pulsed spallation neutron source facility. Neutron imaging can be utilised to visualise the water distribution inside polymer electrolyte fuel cells (PEFCs). Particularly, energy-resolved neutron imaging is a methodology capable of distinguishing between liquid water and ice, and is effective for investigating ice formation in PEFCs operating in a subfreezing environment. The distinction principle is based on the fact that the cross sections of liquid water and ice differ from each other at low neutron energies. In order to quantitatively observe transient freezing and thawing phenomena in a multiphase mixture (gas/liquid/solid) within real PEFCs with high spatial resolution, a pulsed neutron beam with both high intensity and wide energy range is most appropriate. In the validation study of the present work, we used water sealed in narrow capillary tubes to simulate the flow channels of a PEFC, and a pulsed neutron beam was applied to distinguish ice, liquid water and super-cooled water, and to clarify freezing and thawing phenomena of the water within the capillary tubes. Moreover, we have enabled the observation of liquid water/ice distributions in a large field of view (300 mm × 300 mm) by manufacturing a sub-zero environment chamber that can be cooled down to −30 °C, as a step towards in situ visualisation of full-size fuel cells.

Spatially resolved monitoring of the catalytically active state and online catalytic activity measurements were applied to track the fast transient phenomena occurring along the axial direction of a NSR catalyst bed. This methodology clarified the distribution of stored NOx as well as the cause of NOx spike emission.

A bifunctional pathway for selective catalytic reduction (SCR) with NH3 was established using a mixture of WO3/ZrO2 possessing strong acidity and CeO2 possessing moderate redox activity. The physical mixture (tight contact) of WO3/ZrO2 (4.2 W/nm2) and CeO2 provided enhanced SCR reactivity but did not improve the redox property assessed by NO oxidation. No improvement of the SCR conversion, however, was observed for mixtures of individual pellets (loose contact), suggesting the requirement of submicrometer-level proximity of the acidic sites to the redox centers. WO3/CeO2 (5.3 W/nm2) with intermediate acidic strength had higher SCR and NO oxidation rates than the aforementioned physical mixture of WO3/ZrO2 and CeO2. The weakly basic sites (OH species) on CeO2 were replaced stoichiometrically with strongly acidic sites on the WO3 domains along with an increase in the W density (0–24.4 W/nm2), and monoclinic WO3 crystallites then formed at approximately 10 W/nm2. The dispersed WO3 was in a distorted octahedral environment in all WO3/CeO2 samples. The intrinsic SCR reactivity was controlled by only the W surface density; the SCR rate (per surface area) increased within the polytungstate submonolayer region (

It is well known that the performance of monolithic catalysts is limited by gas transport resistance in the washcoat layer. Gases are transported via two types of pores within the washcoat layer: primary pores, which exist inside the particle of catalyst support material (e.g., Al2O3), and secondary pores, which are voids among particles of the catalyst support material. Primary pores play an important role in the effectiveness of catalytically active components such as Pt, Rh, and Pd, while secondary pores facilitate gas transport in the washcoat layer. This paper reports the characterization of secondary pores and their effect on gas transport. In order to evaluate the gas transport properties of a washcoat layer, effective gas permeability was measured. Four samples with different pore morphologies were prepared, and their secondary pore properties were characterized with scanning electron microscopy, mercury porosimetry and synchrotron X-ray computed tomography. The obtained pore properties were correlated with the effective gas permeability, and based on the obtained correlation, we formulated a model for the gas permeability of the pores. This new model was compared to the conventional Kozeny-Carman equation.

Au-Ni bimetallic clusters were identified as possible automobile catalysts that do not contain a platinum-group metal (PGM). The Au-Ni bimetallic clusters were prepared as nanoparticles of Au and Ni using a polyol method. The oxidation states of the Au and Ni species and catalytic activities were studied simultaneously under a NO-CO stream using time-resolved operando X-ray absorption fine structure (XAFS) analysis. Under the investigated reaction conditions, the clusters pretreated by O 2 initially composed of mixtures of Au and NiO were easily reduced to bimetallic Au-Ni nano-particles. The Au atoms promote the release of oxygen from nearby NiO within the cluster. The resulting Au-Ni alloy species exhibit NO purification activity matching that of Rh.

The stoichiometric NO–CO reaction was studied over Cu/CeO2 catalysts prepared with different Cu loadings and specific surface areas of CeO2 to investigate the relationship between catalytic activity and the copper–ceria interaction. XRD, ESR and H2-TPR results revealed that CuO species interacted with CeO2 in three structurally different forms: isolated Cu2+, a highly dispersed CuO film, and large CuO particles. The CuO film showed a higher NO–CO reaction activity than the other species. An Operando XAFS study revealed that the reduction of the CuO film during the NO–CO reaction occurred at the Cu–O–Ce interface. Thus, we concluded that the most suitable CuO structure to effectively exploit Cu–O–Ce interface sites in the NO–CO reaction is a two-dimensionally dispersed CuO film.

Reaction profiles of diatomic molecules, $$\hbox {O}_2, \hbox {N}_2$$ , and NO, on a transition $$d$$ -metal surface were semi-empirically calculated using a new approach based on a bond-energy bond-order (BEBO) model. The BEBO model could be a useful relation for describing reaction configurations. In this work, we introduce a new semi-empirical model which combines density functional theory (DFT)-based interaction parameters with the empirical Miyazaki BEBO model and demonstrate that our model could also be used successfully in previous DFT calculation results. The predictions calculated using this model, such as adsorption energies and adsorption geometries of incoming gas molecules, are close to previous experimental and theoretical results. In particular, the most remarkable point is that previous DFT calculation results and experimental results are available to our procedure. In other words, our model could be extremely simple but powerful.

Highly dispersed FeOx was impregnated onto CeO2 using the unique precursor Na/Fe-ethylenediaminetetraacetate (NaFeEDTA) at varying Fe surface density (0–1.5 Fe/nm2). These catalysts were used for NO reduction by CO and were compared to a more traditional Fe(NO3)3 precursor impregnated on Na-promoted CeO2. Extensive characterization and spectroscopic measurements showed that NaFeEDTA produced a narrower distribution of smaller, noncrystalline, surface FeOx species with excellent redox cyclability (Fe3+ ↔ Fe2+). The NaFeEDTA catalysts exhibited corresponding higher steady-state activity for NO reduction by CO. In situ X-ray absorption spectroscopy with simultaneous gas-phase monitoring indicated that NO conversion began concurrent with reduction of Fe and Ce, suggesting that NO reduction occurred at a reduced Fe–O–Ce interface site. These results illustrate a new synthesis–structure–activity relationship for NO reduction by CO over redox-cycling FeOx sites that may support future rational design of emission...

Polymer electrolyte fuel cells (PEFCs) have been actively developed for a wide range of power generation applications. At the high power densities required for automotive applications, sophisticated water management is vital to further improve cell performance. In particular, the gas diffusion layer (GDL), which includes a microporous layer (MPL), plays a crucial role in optimizing both water drainage and gas transport between the catalyst layer and gas channels. The present work studied the effect of cathode MPL porosity on the water distribution in the GDL. The results show that cells in which MPL materials have larger, micron-sized pores exhibit better performance. Advanced 4D operando X-ray imaging (3D structure plus time) was employed to analyse the water content in GDLs, and demonstrated that the superior performance of cells with large MPL pores is due to the efficient formation of water pathways. These pathways are based on water clusters allowing percolation in the through-plane direction from the bottom to the top of the GDL. Such pathways decrease the liquid water level in the entire cathode GDL. Especially, large MPL pores merge numerous small liquid water pathways in the catalyst layer and stabilize them morphologically, thus creating primary pathways for effective water drainage.

To suppress sintering of Rh supported on an oxide, the interaction between Rh and the support oxide was investigated. To eliminate the structural instability effect of the support oxide on Rh sintering, ZrO2 doped with a rare earth element was used in this study. La doping was found to be most effective for maintaining a specific surface area and the tetragonal phase of ZrO2 after the aging test at 1273 K in air. On this stabilized La-ZrO2 surface, Nd2O3 was introduced, with the aim of investigating its interaction with the supported Rh. Transmission electron microscopy observation with energy dispersive X-ray analysis showed that Nd enrichment existed around the surface of the primary particle of La-ZrO2. Investigations with hydrogen-temperature programmed reduction and extended X-ray absorption fine structure revealed that the supported Rh interacted with Nd2O3 on the surface of the La-ZrO2 and Rh–O–Nd bond formation in oxidizing atmosphere was the origin of the interaction. After a redox aging test at 1273 K, it was found that Rh sintering behavior depended on the Nd2O3 surface enrichment amount and sintering suppression was obtained with a 1–2 wt% Nd2O3 surface enrichment amount. This improvement was caused by the anchoring effect of the Nd2O3-enriched surface layer against supported Rh sintering. This study sets out a way to suppress Rh sintering by an adequate control of the interaction between supported Rh and Nd2O3 on the surface of stabilized ZrO2.

Using a time resolved X-ray absorption spectroscopy (XAS) technique, we studied an in situ dynamic observation of sintering for Pt particles supported on a ceria-based oxide and Al2O3 supports under cyclic oxidizing/reducing conditions at 800 °C. The effect of the support oxide and the amount of Pt loading on the Pt sintering was investigated. The sintering of Pt particles in 2 wt% Pt/ceria-based oxide could be inhibited, when compared to in 2 wt% Pt/Al2O3. Moreover, 0.5 wt% Pt and 1 wt% Pt/ceria-based oxide with a lower Pt loading brought higher stability of Pt against sintering. For a 0.5 wt% Pt/ceria-based oxide catalyst, sintering was completely inhibited and highly dispersed Pt particles (particle size; 1.5 nm) were maintained under redox cycling at 800 °C. These results lead to the conclusion that Pt–O–Ce bond formation on the surface of a ceria-based oxide under oxidative conditions in redox cycling inhibits the sintering of Pt particles, and that the Pt–O–Ce anchor site (its strength and number) has an important role in the sintering inhibition of Pt particles on ceria-based oxide. In addition, we note and discuss apparent change in the oxygen storage/release performance of ceria-based oxide from the viewpoint of the Pt particle size and the intrinsic bulk behavior of ceria-based oxide.

Both the behaviors of sintering and reactivation of Pt and Rh on various metal oxide supports were investigated by TEM, CO pulse chemisorption and XAFS analysis. The results suggest that phenomenon of reversible sintering and re-dispersion to reduced, active metallic sites is related to the electron density of O atoms in support and to the crystal structure of support. As a result of in situ XAFS and in situ TEM analysis, Pt reversible sintering and re-dispersion phenomenon was observed on CeO2 based metal oxide. The Pt re-dispersion process proceeds by the repetition of (1) migration of Pt oxide from the surface of large Pt particles, (2) adsorption of Pt oxide on the surface of CeO2 based metal oxide by strong Pt–O–Ce interaction and (3) reduction Pt oxide and Pt–O–Ce bond. To achieve a good balance between activity and the sintering suppression, CeO2 based metal oxide is selected as Pt support, and ZrO2 is used as Rh support. The blended catalyst of Pt on ceria based oxide and Rh on ZrO2 has higher activity after aging.

Pt–O–Ce bond formation under suitable oxidative conditions on the surface of a catalyst support inhibits Pt particle sintering and promotes the redispersion of agglomerated Pt particles. In the present study the influence of Pt loading on changes in the catalytic activity and Pt particle size was evaluated for aged and regenerated Pt/CeO2-based catalysts. Catalysts with a lower Pt loading exhibited less catalytic deactivation and Pt sintering. There was an ideal Pt loading for which regeneration restored the Pt particle size and the catalytic activity to the same values as for the fresh state. This ideal Pt loading is discussed in terms of Pt anchor sites by considering the structure and composition around Pt on a CeO2-based catalyst.

Unexpectedly large amounts of CO adsorption have resulted from a pulse adsorption experiment at 323 K, giving about 300% Pt dispersion in a Pt/cerium-based oxide catalyst. An in situ diffuse reflectance infrared Fourier transform spectroscopic investigation on a Pt/cerium-based oxide during CO adsorption has revealed that carbonate species on the cerium oxide surface are responsible for the unrealistically large CO adsorption at 323 K, as a result of CO spillover. Lowering the temperature to 195 K considerably diminished the amount of CO adsorption. The size of the Pt particles in the Pt/cerium-based oxide catalyst was determined by CO pulse adsorption at 195 K and showed good agreement with the particle size determined by X-ray diffraction and low energy ion scattering. This indicates that CO pulse adsorption at 195 K is a useful technique to reliably estimate the Pt particle size in a Pt/cerium-based oxide catalyst. © 2009 Elsevier B.V. All rights reserved.

The Pt oxidation state and nanostructure on a ceria-based oxide support were characterized after sequential oxidative, reductive, and re-oxidative treatments using X-ray photoelectron spectroscopy and transmission electron microscopy. The Pt oxidation state and nanostructure depended on the treatment atmosphere: an oxidized Pt monolayer spread along the primary particle surface of the ceria-based oxide support in the oxidized catalyst, whereas metallic Pt existed as particles of 1–2 nm in diameter in the reduced catalyst. Therefore, on the ceria-based oxide surface oxidized Pt formed a nanocomposite oxide with Ce under an oxidative atmosphere and reversibly changed to metallic Pt particles under a reductive atmosphere. The formation of this surface nanocomposite oxide is evidence of the strong interaction between oxidized Pt and CeO 2 that involves the formation of a Pt–O–Ce bond, which stabilizes Pt against sintering and redisperses agglomerated Pt particles under an oxidative atmosphere.

Two novel high-temperature reactors for in situ X-ray absorption spectroscopy (XAS) measurements in fluorescence are presented, each of them being optimized for a particular purpose. The powerful combination of these reactors with the turbo-XAS technique used in a dispersive-XAS beamline permits the study of commercial three-way catalysts under realistic gas composition and temporal conditions.

Suppression of noble metal sintering is a very important approach in the development of automotive three-way catalysts. The investigation into the Pt sintering behavior revealed that the formed Pt–O–M (M: cation of oxide, i.e., cerium oxide) bond acted as an anchor to suppress the Pt sintering, and that the strength of the Pt-oxide-support interaction was well correlated with the electron density of oxygen in the support oxide. To achieve a good balance between catalytic activity and the sintering suppression, ceria based oxide support was verified to be suitable for Pt, and zirconia based oxide support was appropriate support for Rh. Through optimizing the configuration of Pt and Rh in the catalyst, a novel three-way catalyst was developed successfully, and this catalytic activity is far superior to the conventional catalyst, but with lower noble metal content.

Operando X-ray absorption fine structure (XAFS) investigations were performed on Pt/γ-Al2O3 during the total oxidation of C3H6 in reducing and oxidizing atmospheres. Study of the Pt valance state and catalytic conversion behavior as a function of temperature revealed that both the creation of metallic Pt sites and the activation of adsorbed species on Pt are important for the functioning of the catalytic reaction at low temperature.

Reduction rates of rhodium supported on alumina were investigated with in situ time-resolved X-ray absorption fine structure (XAFS). The catalytic sample was prepared with 0.5-wt% rhodium on the alumina powder by a usual impregnation method. Two types of XAFS techniques were applied for the experiments: energy-dispersive XAFS and usual step-scanning XAFS. The reduction rates of the rhodium supported on alumina after oxidizing treatment at 500 °C were measured with dispersive XAFS. The reducing condition was with 3% H2 in He at various temperatures from 100 to 250oC. The spectra of Rh K-edge X-ray absorption near edge structure (XANES) were acquired every 0.2 s. The oxidation state of the rhodium was evaluated by the energy shift of Rh K-edge. The reduction rate of the rhodium was on a line in an Arrhenius plot. Reduction of the rhodium on the alumina in 3% H2 in He at 900 °C after high temperature oxidization at 900 and 1000 °C were measured with step-scan XAFS. Though a portion of the rhodium was reduced in a few minutes, the residual rhodium was hardly reduced. The hardly reducible rhodium was considered to be reacted with the alumina support and lost catalytic activities. The ratio of the deactivated rhodium has been estimated as a function of the oxidization temperature and period. Copyright © 2008 John Wiley & Sons, Ltd.

Sintering–redispersion of Pt and deterioration–regeneration of catalytic activity on Pt/MgO as automotive exhaust catalyst were studied. No Pt sintering was observed after air aging up to 1173 K. Pt L 3 -edge extended X-ray absorption fine structure results revealed the formation of an Mg 2 PtO 4 -like compound at the MgO surface and stabilization of oxidized Pt after air aging. Interaction between Pt and MgO involved in the formation of this Mg 2 PtO 4 -like compound likely provides an anchoring effect that prevents Pt sintering. After redox aging at 1073 K, Pt particles of ca. 20 nm were observed by X-ray diffraction and transmission electron microscopy (TEM). TEM images revealed that sintered Pt redispersed into smaller Pt particles of 2–5 nm on sequential oxidation–reduction treatment at 1073 K. Interactions involved in the formation of the Mg 2 PtO 4 -like compound should be the driving force for this redispersion. The redispersion behavior led to regeneration of the catalytic activity of Pt/MgO in a simulated automotive exhaust reaction.

In order to identify the initiation step in the photodegradation of poly(2,6-butylenenaphthalate)- block -poly(tetramethyleneglycol) (PBN–PTMG), we undertook its photolysis with monochromatic irradiation. We discuss the initiation reaction on the basis of the analytical results for the PBN–PTMG in the presence or absence of 2,2′-dihydroxy-4-methoxybenzophenone as a UV absorber, 2-hydroxy-4-methoxybenzophenone as a UV absorber, β-carotene as a quencher of singlet oxygen or methylene blue as a photosensitiser, respectively. The PBN–PTMG containing 2,2′-dihydroxy-4-methoxybenzophenone exhibits better resistance to the incident light of ca. 370 nm corresponding to the absorption of the n, π * transition of the carbonyl group in the PBN block than the PBN–PTMG containing 2-hydroxy-4-methoxybenzophenone. The PBN–PTMG containing β-carotene shows similar photodegradation tendencies as that of the PBN–PTMG without β-carotene. In contrast, the PBN–PTMG with methylene blue is not degraded by monochromatic radiation in the range λ = 600–690 nm. These facts indicate that singlet oxygen does not participate in the initiation reaction of the photodegradation of the PBN–PTMG. Therefore, we concluded that the photodegradation of the PBN–PTMG is induced through the hydrogen abstraction by carbonyl groups in n, π * excited states.

Three types of CeO2–ZrO2 (Ce:Zr = 1:1 molar ratio) compounds with different oxygen storage/release capacity (OSC) were characterized by means of the Ce K-edge and Zr K-edge XAFS. In order to investigate the relationship between the OSC and local structure, the quantitative EXAFS curve-fitting analysis was applied. By enhancing the homogeneity of the Ce and Zr atoms in the CeO2–ZrO2 solid solution, the OSC performance increased. Additionally, from the XRD analysis, the homogeneous CeO2–ZrO2 solid solution has an ordered cation arrangement, and exhibits the highest OSC. The crystal structure of this CeO2–ZrO2 solid solution is usually termed as “κ-CeZrO4 phase”. However, the OSC performance of κ-CeZrO4 degrades upon a high-temperature treatment under an oxidative atmosphere. The fresh κ-CeZrO4 was aged at 973, 1,273 and 1,473 K under an oxidative atmosphere, respectively. The OSC performance deteriorated as: the fresh sample ≈973 > 1,273 > 1,473 K-aged samples. We also found that, if the temperature was beyond 1,273 K, the Ce/Zr ordered arrangement would collapse and the local structure around Ce and Zr ions would also changed remarkably. These results indicated that OSC was strongly dependent on its atomic structure.

Ceria–zirconia solid solution has a function as an oxygen storage material, which keeps air to fuel ratio (A/F) on a stoichiometric composition at the surface of three-way catalyst (TWC) for automotive exhaust. When A/F could be kept stoichiometric, TWC shows good catalytic activity. At first, ceria which dissolves 20 mol% of zirconia was developed by Ozawa et al. in 1987. After that, the ceria–zirconia solid solution was improved to achieve a complete solubility in the solid state at nano-level by surfactant modified homogeneous coprecipitation (J catal 169:490, 1997). Nano-level solid solution of ceria and zirconia could have been made by various methods. Those materials have similar amount of oxygen storage capacity (OSC). The improvement of OSC comes from the larger amount of bulk oxygen that can contributes OSC by the larger amount of zirconia dissolving into ceria (Catal Lett 33(1–2):193–200 1995). Solvothermal synthesis is usually done in a higher temperature than that can be reached under atmospheric pressure. The higher temperature accelerates generation of precipitation; however, a pressure vessel is necessary, and such a hermetically closed system is unsuitable to the material synthesis of the low-value-added product. Atmospheric pressure solvothermal (APS) synthesis was applied to ceria-zirconia solid solutions in this study. The APS ceria-zirconia showed larger amount of OSC. The excellent OSC performance was presumed to come from further uniformity of zirconium ions in the ceria lattice.

Ceria-zirconia solid solution is one of the most important components of three way catalyst (TWC) for cleaning automotive exhaust. Ceria-zirconia solid solution has a function as an oxygen storage material, which keeps air to fuel ratio (A/F) at the surface of TWC on a stoichiometric composition. The dissolved zirconia into ceria lattice makes cerium ions to be reduced easier and enhances especially bulk oxygen to release. However, there is a large difference of oxygen storage capacity (OSC) between a theoretical value and that of the prior ceria zirconia solid solutions. The cause of the large difference of OSC might be come from the inhomogeneous dispersion of Zr ions in ceria lattice. Atmospheric pressure solvothermal (APS) process was applied to ceria-zirconia solid solutions in this study. The APS ceria-zirconia showed excellent OSC. The excellent OSC performance was presumed to come from further uniformity of zirconium ions in the ceria lattice.

Sintering inhibition mechanism of Pt in Pt/ceria-based oxide catalyst under oxidizing condition at high temperature was studied by several analysis techniques. Pt in a Pt/ceria-based oxide catalyst did not sinter after aging treatment at 800 °C in air, but did sinter in a Pt/Al 2 O 3 catalyst. Using X-ray absorption analysis, we found that the Pt O Ce bond (i.e., the Pt-oxide–support interaction) acted as an anchor and inhibited the sintering of Pt particles on ceria-based oxide. As a result of further systematic investigation on various Pt catalysts, clearly there was an excellent correlation between the strength of the Pt-oxide–support interaction and the electron density of oxygen in the support oxide. The sintering inhibition effect on Pt can be controlled by the electron density of oxygen in the support through the Pt-oxide–support interaction.

The wavelength dependence of the photodegradation of poly(2,6-butylenenaphthalate- co -tetramethyleneglycol) (PBN-PTMG), has been investigated using monochromatic radiation supplied from the Okazaki Large Spectrograph. From our results, we conclude the following. Main chain scission occurs when PBN-PTMG is exposed to wavelengths of 380 nm and shorter. Remarkably, the formate, propyl, aldehyde and the aliphatic ester groups are all formed by monochromatic irradiation at 370 nm and 380 nm. The proportion of the gel fraction is greatly enhanced when radiation is carried out with monochromatic light of ca. 380 nm. The threshold wavelength for the photodegradation of poly(2,6-butylenenaphthalate- co -tetramethyleneglycol) is ca. 380 nm.

The CeO 2 -ZrO 2 solid solution is the most important oxygen storage/release material for use in automobile catalysts. In particular, the ceria-zirconia solid solution with a pyrochlore structure exhibits the highest oxygen storage capacity (OSC). In this study, CeO 2 -ZrO 2 solid solutions containing Y 2 O 3 were synthesized and their OSCs were measured to clarify the influence of an ordered arrangement of Ce and Zr ions on the OSC. As a result of this study, it is concluded that an ordered arrangement of Ce and Zr ions markedly improves the OSC of CeO 2 -ZrO 2 solid solutions.

As an important oxygen storage material, ceria-zirconia solid solution is widely used in automotive three-way catalysts. For the Ce-Zr solid solution being usually used with a noble metal, the evaluation of oxygen storage capacity (OSC) should be conducted with the Ce-Zr solid solution loaded with a noble metal. The measured OSC of noble-metal-loaded Ce-Zr solid solution consists of two parts: the stored oxygen within the solid solution itself and the adsorbed oxygen on the loaded noble metal particles. Therefore, it is very necessary to clarify the influence of metal loading on the measured OSC in order to ascertain the exact OSC of the solid solution itself. In this research, the authors attempted to clarify the above issues by characterizing the OSC performance of Ce-Zr solid solutions with platinum (Pt) loading from 0.0001-10 mass%. We found that increasing the amount of Pt loading increases the oxygen storage and release rates and that increasing the temperature also increases the oxygen storage rate, although the oxygen release rate is not affected by increasing the temperature. The apparent OSC reached saturation over a certain amount of Pt loading and temperature. The saturated OSC increased with increasing temperature.

Ceria-zirconia (Ce-Zr) solid solution is widely used as an oxygen storage material, which is a key component in the automotive three-way catalysts. The Ce-Zr solid solution is usually used with noble metals supported on their surface. Thus the evaluation of oxygen storage capacity (OSC) should be conducted on the Ce-Zr solid solution loaded with a noble metal. The measured OSC of noble-metal-loaded Ce-Zr solid solution consists of two parts; one is the stored oxygen within the solid solution itself, and the other is the adsorbed oxygen on the surface of the supported noble metal particles. Therefore, it is necessary to clarify the influence of the noble metal on the measured OSC, and this will also help to ascertain the exact OSC of the solid solution itself. In this research, the authors tried to clarify the above issues by characterizing the OSC performance on Ce-Zr solid solutions with Pt loading from 0.0001 to 10 wt%. We found that, increasing the Pt loading makes the oxygen storage and release rate higher. Temperature increase also makes the oxygen storage rate higher, however, the oxygen release rate is not affected by the temperature. The apparent OSC saturated above a certain level of Pt loading and temperature. The saturated OSC increased with increasing temperature.

We examined the oxidation reaction of n-C6H14 and SO2 over two types of Pt/ZrO2 catalysts with low (8 m2/g) and high (75 m2/g) surface areas of the ZrO2 supports (referred to as ZrO2-8 and ZrO2-75, respectively). The catalytic activity was evaluated under simulated diesel exhaust gas which simultaneously contained n-C6H14 and SO2. The Pt/ZrO2-75 exhibited a desirably higher selectivity for the complete oxidation of n-C6H14 than that of SO2, as compared with the Pt/ZrO2-8. In order to clarify the cause of this selective oxidation, we investigated the Arrhenius parameter for these oxidation reactions and characterized these catalysts using X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), Transmission electron micrograph (TEM), IR and CO2 temperature-programmed desorption (CO2-TPD) methods. The amount of Pt0 (metal) in the Pt/ZrO2-75 was significantly lower than that in Pt/ZrO2-8, because the high basicity of the ZrO2-75 support stabilized the high oxidation state of Pt such as Pt2+ and Pt4+. It was concluded that the difference in the number of Pt0 sites as catalytic active sites causes the apparent selectivity to change due to the much slower reaction rate for the SO2 oxidation than that for the n-C6H14 oxidation.

Three types of CeO2–ZrO2 (Ce:Zr=1:1 molar ratio) compounds with different oxygen storage/release capacities (OSCs) were characterized by means of the Ce K-edge and Zr K-edge X-ray absorption fine structure (XAFS). In order to investigate the relationship between the OSC and local structure, the quantitative EXAFS curve-fitting analysis was applied. By enhancing the homogeneity of the Ce and Zr atoms in the CeO2–ZrO2 solid solution, the OSC performance increased. Especially, the atomically homogeneous Ce0.5Zr0.5O2 solid solution exhibited the highest OSC among these CeO2–ZrO2 samples. Additionally, the local oxygen environment around Ce and Zr was remarkably modified by enhancing the homogeneity of the CeO2–ZrO2 solid solution. It was postulated that the enhancement of the homogeneity of the CeO2–ZrO2 solid solution and the modification of the oxygen environment would be the source for the OSC improvement.

To compare the contribution of degradative factors to weathering of a thermoplastic polyester elastomer (TPEE) photo-, thermal conditions and water were selected as the degradative factors. Experiments on photodegradation, thermal degradation and hydrolysis of TPEE were carried out. Spectral irradiation using sharp-cut filters with a xenon lamp, photodegradation under several temperature conditions and immersion in water during photoirradiation were also performed. The results of these experiments were compared with those of outdoor and accelerated weathering tests. The following conclusions were obtained under the experimental conditions: (1) a major factor of the degradation are ultraviolet rays below 310 nm; (2) an increase in temperature accelerates the rate of degradation reaction; and (3) the presence of water increases the amount of gel formation caused by cross-linking reaction.

Catecholatoiron complexes were isolated in the crystalline or non-crystalline form from the reaction solution of catechols with FeCl 3 in the presence of pyridine in THF; they form a functional model system for catechol dioxygenases. Two types of complex were obtained, depending on substituent on catechol and pyridine: [FeCl (catechol)(pyridine)](pyridine) and [FeCl 2 (catechol)] − ·2[pyridine·H] + . An X-ray quality single crystal was obtained with the 3.5-di-tert-butycatecholato(2,6-lutidine)iron chloride complex: it is monoclinic, space group C2 m , with cell dimensions a = 11.947(3), b = 16.122(3), c = 14.725(2) A , β = 100.38(2)°, and Z = 2. The [Fe 2 (catechol) 2 Cl 4 ] 2− anion forms a dinuclear complex with two crystallographically equivalent iron centers, each metal ion of which is in a five-coordinated distorted square-pyramidal geometry with two chloride anions and two oxygen atoms of two bridging catechol molecules. Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) studies have revealed that the other isolated complexes are also dimeric in the solid state and become monomeric in the THF solution. The presence of FeCl bonding and its conversion to Fe-pyridine in solution are shown by the Br K-edge EXAFS analysis of the analogous bromide complex.

Thermoplastic polyester elastomers (TPEE) are useful as new materials covering the region between rubbers and plastics. At present, the uses under outdoor conditions have increased. However, weatherability of TPEE is not clear. We have studied weathering of TPEE, by means of GPC, TG/DTA, FT-IR and 1 H-NMR and other methods. In conclusion, (1) Ether parts of the soft segment in the polymer are degraded selectively and ester bonds are formed. (2) In both outdoor exposure tests and the accelerated weathering test, main chain scission and crosslinking reactions occur. (3) There was a clear difference between tendencies of degradation by outdoor exposure and the accelerated weathering test. The amount of crosslinked products which formed during the accelerated weathering test was larger than that formed during the outdoor exposure tests.

代表的な加硫ゴムであるstyrene-butadiene rubber (SBR) の明色配合試料をモデル試料としてとりあげ, 新しいウェザリング解析の手法を検討する目的で, いくつかの分析手法の適用を試みた. その結果, 表面・界面物性解析装置による深さ方向の「比切削抵抗」による評価法が加硫ゴムの劣化解析法として適用可能であること, また圧縮方向の振動荷重によるTMA測定は, 引張り方式やねじり方式での粘弾性の測定が困難な, 劣化の進行した試料に有効であること, さらに表面の変色が少ない試料では, 第1種相関PAS法によっても劣化解析が行えることがわかった. 暴露条件の影響に関しては, 1年以上の宮古島暴露試料では, 0.5年までの宮古島暴露試料や銚子暴露試料と異なり, 暴露により表面部分に生成した酸化層により, 内部への劣化の進行が抑制されていることが示唆された.