齋藤 守弘

Metal fluoride added carbon anodes treated by pre-electrolysis were investigated for electrolytic production of nitrogen trifluoride (NF3) in molten NH4F center dot KF center dot 4HF at 100 degrees C. The conditions for pre-electrolysis were first optimized using a graphite sheet anode as a model anode. The formation of Fluorine-graphite intercalation compounds (fluorine-GICs) with semi-covalent C-F bonds, (CxF)(n), on the MgF2 and CaF2 added carbon anode surface was accelerated by pre-electrolysis at potentials less than 4.0 V. Critical current densities (CCD) on the MgF2 added carbon anodes pre-electrolyzed under various conditions were determined, and the highest CCD was 290 mA cm(-2) obtained for that pre-electrolyzed at 3.5V for 500 C cm(-2). This anode was successfully used in the electrolysis at 100 mA cm(-2) for 290 h and the maximum NF3 current efficiency was 55%. From these results, it was concluded that the metal Fluoride added carbon anode treated by pre-electrolysis has a high potential for electrolytic production of NF3 at higher current density. (c) 2010 Elsevier Ltd. All rights reserved.

In order to clarify the effect of surface atomic structure of oxygen reduction reaction (ORR) activity for Pt/C catalysts, cubic and cuboctahedral Pt nanoparticles (NPs) colloidal solutions were prepared from K2PtCl4 solutions using sodium polyacrylate (PAA) as a capping reagent, and furthermore the shape-controlled Pt NPs were deposited on a Ketjen Black support. The cubic and cuboctahedral Pt/C catalysts (Pt-cubic/C and Pt-cuboctahedral/C) gave characteristic H-2 absorption/desorption peaks in the CV curves attributed to their crystal facets. The Pt-cuboctahedral/C having the (100) and (111) faces showed higher ORR activity than a commercially available polycrystalline Pt/C and the Pt-cubic/C composed of mainly (100) facet.

Perovskite and Mn oxide nanosheet-based electrocatalysts were synthesized as the cathode of anion-exchange membrane fuel cells (AEMFCs), and their oxygen reduction reaction (ORR) activities and AMFC performances were evaluated. Perovskite La0.6Sr0.4MnO3 (LS0.4M/KB) loaded on Ketjen Black exhibited the highest ORR activity (onset potential: ca. 0.9 V vs. reversible hydrogen electrode (RHE) and efficiency for 4-electron reduction of O-2: > 90%), and achieved a maximum power density of ca. 92 mW cm(-2).

To improve the practical capacity of TiO2(B), optimization of precursor (K2Ti4O9 and Cs2Ti5O11), solvent (EC+DEC, EC+DMC and EC+DMC) in electrolyte and homogeneity (mixing with a mortar or wet-ball milling machine) of Ketjen Black (KB) as conductive agent was conducted. Use of Cs2Ti5O11 precursor reduced the content of TiO2 anatase as an impurity in the obtained TiO2(B). Choice of DMC solvent with the highest dielectric constant (3.1) and the lowest viscosity (0.59 cP) and improvement of the homogeneity of KB conductive agent enhanced the Li+ ion and electron conductivities in the electrode. As a result, the optimized TiO2(B) electrode exhibited a high discharge capacity of 314.4 mAh g(-1) in 1 M LiPF6/EC+DMC(1:2), which corresponds to ca. 93.9% of the theoretical capacity of TiO2(B), 335 mAh g(-1). Moreover, a high rate capability of 118.5 mAh g(-1) even at 10 C was also achieved.

The (ZrO2-1.6P(2)O(5))-PTFE composite electrolytes have been prepared by mixing PTFE powders with different particle sizes and the shell-core-type ZrO2-1.6P(2)O(5) electrolyte, synthesized by solid state reaction with diammonium hydrogen phosphate, to improve the mechanical strength of the electrolyte. The H-2 gas permeability decreased and the cell performances improved with decreasing PTFE-particle size. The aging at 0.4 V above 443 K enhanced the ITFC performance owing to the penetration of the electrolyte to the carbon paper. The maximum output power enhanced by 63% after 15 h of aging at 573 K.

The extended X-ray absorption fine structure (EXAFS) was measured to study the effects of the local structures on the Li-ion transfer in the La2/3-xLi3TiO3 perovskite model compound with different lanthanum ion concentrations. The results indicate that the local structure is more distorted and the interatomic distances of Ti-La and Ti-O-Ti become shorter with the decrease of lanthanum ion concentration. The change in Li-ion conductivity with different lanthanum ion concentration is well explained by the relation between the estimation of activation energy with which Li ions hop through the bottleneck and the results of local distortion by EXAFS analysis.

Pure Si platelets (Si-LP, thickness: 100 nm) and Ni layer-laminated Si platelets with different thicknesses (Si/Ni/Si-LP50 (50/50/50 nm) and Si/Ni/Si-LP30 (30/30/30 nm)) were prepared by a vapor deposition method, and their charge/discharge properties were investigated as alternative negative electrode materials to graphite for lithium-ion batteries. The shape of thin platelet effectively relieved the stress during the alloying and de-alloying processes, and improved the charge/discharge cycleability as compared with a commercially available Si powder. In particular, the laminated platelet samples showed very good cycleability, probably because of a shorter diffusion length of Li+ ions in the Si layers and an improved mechanical strength by the presence of the Ni layer.

Li+ ion insertion/extraction properties of TiO2(B) powder, which was prepared from a K2Ti4O9 precursor by ion-exchange and dehydration, was investigated as a high-potential negative electrode. The irreversible capacity greatly decreased from 124 mAh g(-1) ca. 40 mAh g(-1) when the lower potential limit was raised from 1.0 V to E >= 1.2 V, which indicated that the irreversible capacity mainly originated from surface reactions, such as solvent decomposition, at E <= 1.2 V in the first cycle. In galvanostatic intermittent titration tests, large polarization was observed at the beginning and the end of charging. This clearly indicated that a slow process is involved in the insertion reaction at the beginning and the end of charging, which causes solvent decomposition at potentials lower than 1.4 V. The reversible capacity was greatly improved to 246 and 276 mAh g(-1) an elevated temperature of 60 degrees C and at a lower rate of C/60, respectively. The TiO2(B) sample contained ca. 14 wt% of the anatase phase as an impurity, and a reduction of the anatase phase was found to be effective for an increase in reversible capacity at moderate charge/discharge rates.

Pt/Au/C and Pt/Pd/C core-shell catalysts were prepared from Au/C and Pd/C cores with different core sizes using under potential deposition (UPD) of Cu, and the activity for oxygen reduction reaction and durability of the Pt/Au/C and Pt/Pd/C catalysts were investigated. Pt/Au/C and Pt/Pd/C core-shell catalysts showed higher mass activities than a commercially available Pt-2.8nm/C catalyst, and hence they are promising for reducing the Pt usage in PEFCS. In potential cycling durability tests between 0.6-1.0 V, opposite effects of core size on were observed for Pt/Au/C and Pt/Pd/C. For Pt/Au/C, smaller cores gave high durability, whereas for Pt/Pd/C, larger cores gave high durability comparable with the Pt-2.8nm/C.

To understand the ionic and non-ionic species in (CH3)(4)NF center dot mHF, (CH3)(3)N center dot mHF, (C2H5)(4)NF center dot mHF, and (C2H5)(3)N center dot mHF melts, the structures of these melts were investigated by infrared spectroscopy, NMR and high-energy X-ray diffraction. IR spectra revealed that the complex fluoride anions such as (HF)(n)F- (n = 1, 2, 3) and molecular HF are present in all melts. Ionic conductivity and viscosity of these melts were measured and correlated with their cationic structure. The ionic conductivity of the R4N+-systems was higher than those of corresponding R3NH+-systems. (CH3)(4)N+ and (CH3)(3)NH+ cation gave higher ionic conductivity than (C2H5)(4)N+ and (C2H5)(3)NH+ cation, respectively. It was concluded that these effects on ionic conductivity can be explained by the cationic structure and the concentration of molecular HF in the melts.

The influence of CO2 in the oxidant gas on the cell performance of anion-exchange membrane fuel cells was investigated using a three-electrode single cell with a reversible hydrogen electrode (RHE). The overpotential of the cathode was hardly changed by the presence of CO2, while the overpotential of the anode increased after the introduction of CO2 at the cathode. The high anode overpotential was caused by a high CO32- concentration in the anode catalyst layer, even when most of the CO32- ions in the electrolyte membrane are purged during operation through the self-purging mechanism.

Two kinds of metal thin platelets (Leaf Powder (R), Oike Co., Ltd.) based on Sn and Si were prepared, and their charge/discharge properties were investigated as alternative negative electrode materials to graphite for Li-ion batteries. One was simple metal platelets (M-LP, thickness: 100 nm) and the other was laminated platelets with an inactive Ni layer (M/Ni/M-LP, thickness: 30/30/30 nm). For both Sn and Si platelets, the shape of thin platelets effectively relieved the stress by volume expansion and shrinkage during the alloying and de-alloying processes, and improved their charge/discharge cycleabilities. Particularly, the Si platelets suppressed their agglomeration and pulverization, and much more remained the shapes than the Sn platelets. The lamination with the inactive Ni layer further improved the cycleability, though the specific capacity decreased by its presence. The alloying and de-alloying reaction with Li+ ion was substantially smooth, which was due to a decrease in the diffusion distance of Li+ ion by using the thin platelets. As a result, the Si/Ni/Si-LP exhibited a good capability over ca. 400 mAh g(-1) up to 3C rate.

Proton conducting ZrO2-yP(2)O(5) (y = 1.0, 1.2, 1.4, 1.6, 1.8) electrolytes based on a shell-core structure were synthesized with diammonium hydrogen phosphate by a solid state reaction, and their conductivities were investigated by ac-impedance spectroscopy. Among the ZrO2-yP(2)O(5) compositions, ZrO2-1.6P(2)O(5) showed the highest proton conductivity of 0.13 Scm(-1) at 250 degrees C. The conductivity increased with increasing P2O5 molar ratio and were significantly influenced by heat-treatments in the preparation process. Polytetraflouroethylene (PTFE) was also mixed into these electrolytes in order to improve the mechanical strength and long term durability.

The Mn-doped pyrochlores Pb2Ru1.5Mn0.5O7-delta (PRMns) samples were synthesized by a precipitation method, followed by heat-treatments at temperatures of 300-800 degrees C. Effects of the heat-treatments on their electrocatalytic activities for oxygen reduction reaction (ORR) were examined by semi-steady state voltammetry with a rotating ring-disk electrode in 0.1 M KOH solution at 70 degrees C. The PRMns showed the best ORR activity for the 500 degrees C-heat-treated PRMn. The onset potential of the ORR current was over 1.0 V vs RHE, and the efficiency of 4-electron reduction was almost 100%. The maximum in the ORR activity for the 500 degrees C-heat-treated PRMn resulted from a trade-off effect between their crystallinity and specific surface areas.

The trirutile oxides MTa2O6 (M=Co,Ni,Mg) [MTs] and the substitution products M1-xNxTa2-yLyO6 (N=Mn, L=Sn,Ti,Zr) [M1-xNxTa2-yLy] were prepared by a conventional solid-state reaction. The oxygen reduction reaction (ORR) activities were evaluated with the onset potentials (E-on) of the ORR currents, the disk current densities (i(D)) and the efficiencies (Eff(4)) of 4-electron reduction, measured by a rotating ring-disk electrode (RRDE) technique. All the samples showed ORR activities and the E-on values were around +0.8 V vs. RHE in 0.1 M KOH. The CoTa2O6 electrocatalyst showed the best ORR property of the MTs samples: its Eff(4) value was as high as similar to 80%. With substitution of Ti or Sn, the ORR activities of MgTa1.9T0.1O6, CoTa1.8Sn0.2O6 and NiTa1.9Ti0.1O6 were improved in alkaline solution, compared with those of MTa2O6. In acid solution, the same substitution of Ti and Sn resulted in improvement of Eff(4), but no significant improvements of E-on and i(D).

The proton conducting 0.9MO(2)center dot 0.05In(2)O(3)center dot 1.3P(2)O(5) (M=Ti, Sn, Zr) electrolytes based on a core-shell structure were synthesized by a ball milling method. The core-shell type electrolytes showed the proton conductivities ranging from a higher value than those of Nafion membranes to 10(-5) Scm(-1) at intermediate temperatures of 150-200 degrees C, depending on the heat-treatment conditions. The samples with high conductivity were proved to adopt a core-shell structure by SEM observation, powder XRD analysis and (31)P MAS-NMR measurements. (C) 2008 Elsevier B.V. All rights reserved.

Novel proton-conducting composites were prepared by incorporating molten CsHSO(4) (CHS) into two types of mesoporous silica, MCM-41 with a one-dimensional (1-D) hexagonal structure and MCM-48 with a three-dimensional (3-D) cubic structure. Their proton conductivities (sigma) were measured to examine effects of the incorporation and the dimensionality of the mesopores on their conductivity. Incorporation of proper amounts of MCMs maintained high proton conductivities as high as similar to 10(-3) S cm(-1) at temperatures above the superprotonic phase-transition temperature (T(s): 414 K) of CHS and improved the conductivity by 2 to 3 orders of magnitude at temperatures below T(s). In the case of MCM-41, more than 40 mol% mixing, however, caused steep drops in sigma in both temperature ranges. On the other hand, the CHS/MCM-48 composite showed a linear increase in sigma below T(s) and a gradual decrease in sigma above T(s) with an increase in the MCM-48 content at least up to 60 mol%. X-ray diffraction (XRD) analysis revealed that CHS filled in the MCM mesopores became X-ray crystallographically amorphous and the amount of the amorphous phase increased with an increase in the MCM contents. In the case of the CHS/MCM-48 composites, the activation energy (E(a)) for proton conduction below T(s) drastically came close to that above T(s) by mixing with MCM-48 up to 30 mol%. This indicates that the proton can transport similarly to the conduction mechanism in the superprotonic phase even below T(s). These results suggest that CHS adopts a highly proton-conducting amorphous phase in the mesopores at temperatures below T(s), and that MCM-48 with the 3-D cubic structure is more suitable for formation of high proton-conducting percolation paths. (C) 2008 Elsevier B.V. All rights reserved.

La0.56-yLi0.33TiO3-3yF3y (y = 0.017, 0.05) were prepared by a conventional solid-state reaction from a mixture of La2O3, LiCO3, TiO2. and 10% excess LiF. The variation of the lattice parameter with increase of y value in La0.56-yLi0.33TiO3-3yF3y was different from that in conventional lithium-lanthanum-titanate series perovskite oxides, La0.56-yLi0.33+3yTiO3. Bulk Li-ion conductivities of the La0.56-yLi0.33TiO3-3yF3y are higher than those of La0.56-yLi0.33+3yTiO3. Li-ion conductivity of La0.56-yLi0.33TiO3-3yF3y (y=0.017) was 2.30 x 10(-3) S cm(-1) at 30 degrees C, which is, to our knowledge, one of the highest Li-ion conductivities in the oxide compounds. (c) 2008 Elsevier B.V. All rights reserved.

Three types of titania nanosheet-based materials, a H3O +-exchanged rolled nanosheet (nanotube) (H3O +-NT(Ti)), layered titanate (H3O+-RG(Ti)), and restacked titania nanosheets (H3O+-RE(Ti)) were synthesized by soft chemical methods, and their oxygen reduction reaction (ORR) activities were examined by semi-steady-state voltammetry with a rotating ring-disc electrode at 70°C in 0.05 M H2SO4. All the samples showed similar onset potentials (Eon) of the ORR current, ∼ 0.50 vs. reversible hydrogen electrode, while the efficiencies (Eff 4) of the 4-electron reduction of oxygen depended on their nanostructures, i.e. the stacking morphology of nanosheets, specific surface area and kinds of inserted cation between the nanosheets. Both H 3O+-RG(Ti) and H3O+-RE(Ti) samples showed higher Eff4 values as compared with Cs+-form layered titanate (Cs+-RG(Ti)) and the H+-form restacked titania nanosheets (H+-RE(Ti)). This reveals that the H 3O+ions and the number of the active sites for ORR are related to the ORR activity. The H3O+-RE(Ti) exhibited the best Eff4 value (&gt 90%), which is comparable to that of a conventional 20 mass% Pt/C catalyst. The effects on the ORR activity are also observed in alkaline (0.1 M KOH) aqueous solution, i.e. the H3O +-RE(Ti) exhibited the best Eon (∼ 0.8 V) and Eff 4 values (&gt 90%). ©The Electrochemical Society.

In order to reproduce the observed ionic conductivities and activation energies computationally, the potential parameters (PMs) were optimized for classical molecular dynamic simulations on Li ion conduction in the A-site deficient perovskite solid solution La(0.56)Li(0.33)TiO(3) with disordered A-site ion arrangement. By the use of the optimized PMs, the conductivities and the activation energies were improved considerably from 4.1 x 10(-3) Scm(-1) to 4.4 x 10(-2) Scm(-1) at 800 K and 0.02 eV to 0.2 eV, respectively. The pair correlation functions calculated with the optimized PMs reveal that the Li-ions are located somewhat broadly mainly in the vicinity of the midpoint between the center of the A-site and the center of the bottleneck formed by four O(2-), and that the simulated Li location is significantly related to the conductivity.

Photocatalytic proton reduction and water oxidation have been studied in a tris(2,2'-bipyridyl)ruthenium complex-catalyst system. Pyrochlore-type oxides have been used as proton reduction catalysts with a sacrificial electron donor (Na(2)EDTA) at pH 7 and as water oxidation catalysts with a sacrificial electron acceptor (K2S2O8) at pH 3. Rate constants for the proton reduction were estimated on the basis of photochemical processes. Yb2Ru2O7-delta was found to be the most active catalyst for proton reduction and water oxidation catalyst in this system.

The ternary oxide compositions xZrO(2)-(0-5-x/2)Al2O3-yP(2)O(5)(x=0.8, 0.9, 0.95, 1.0; y=1.0, 1.2, 1.4) and 0.9ZrO(2)-0.05In(2)O(3)-1.4P(2)O(5), xSiO(2)-(0.5-x/2)Al2O3-1.4P(2)O(5)(x=0.9, 1.0) were synthesized by sol-gel methods, and their conductivities were investigated by ac-impedance spectroscopy. The conductivity increased with increasing P2O5 Content and with decreasing heat-treatment temperature. The maximum conductivities reached over 10(-2) Scm(-1) at 150 degrees C for 0.9ZrO(2)-0.05Al(2)O(3)-1.4P(2)O(5) and at 225 degrees C for 0.9SiO(2)-0.05Al(2)O(3)-1.4P(2)O(5).

Metallic ruthenium nano-particles supported on carbon were prepared from Ru(3)(CO)(12) and highly-porous activated carbon by adsorption of the complex under boiling conditions in an acetone or cyclohexane solution, followed by H(2) reduction at 200 degrees C. Occupation of micropores with the precursor all through the carbon surface would diminish the BET surface area and the pore volume, whereas partial restoration of them by heating the material in H(2) flow would be caused by complex decomposition and coagulative growth of Ru nano-particles (3.01 nm in average from TEM observation), which were surely lager in size than the pore diameter (2.15 nm determined by adsorption-isotherm measurements). Ru nano-particles were well dispersed on carbon.

Phase studies and ac-conductivity measurements were carried out in the compositions M(0.8)In(0.2)Li(0.2)P(2)O(7) [MILP] (M=Sn, Zr, Ti). The bulk conductivities were of the order of similar to 10(-5) Scm(-1) at 623 K and higher in the order of TiILP >= ZrILP>SnILP. The activation energies, as expected, became lower in the order of ZrILP<TiILP<SnILP with increasing size of the bottleneck windows for hopping of the Li ions. The order of TiILP >= ZrILP>SnILP in bulk conductivities were not correlated with that of the activation energies probably because of the impureness of the ZrILP sample.

Shell-core type TiP2O7-based electrolytes were synthesized by a low-temperature sol-gel method, and their conductivities were investigated by ac-impedance spectroscopy. The samples heat-treated at 500 degrees C showed higher proton conductivities of 3.8 x 10(-2) - 1 x 10(-2) Scm(-1) at intermediate temperatures (100 - 300 degrees C). The conductivity decreased by reheat-treatments at 600 degrees C and 700 degrees C due to a decrease in the amount of the conductive amorphous shells. However, the mechanical strength of the sample pellet significantly increased by the reheat-treatment. The sample reheat-treated at 600 degrees C kept high conductivities of 8.8 x 10(-3) - 1 x 10(-3) Scm(-1) in a range of 100 degrees C - 300 degrees C.

Two types of oxide nanosheet-based materials, a H3O+-cxchanged layered titanate and restacked titania nanosheets (H3O+-RE) were synthesized by soft chemical methods, and their oxygen reduction reaction (ORR) activities were examined by semi-steady-state voltammetry with a rotating ring-disc electrode at 70 degrees C in 0.05 M H2SO4. Both samples showed similar onset potentials of the ORR, similar to 0.50 vs. reversible hydrogen electrode, while the efficiencies (Eff(4)) of the 4-electron reduction of oxygen depended on their nanostructures, i.e. the stacking morphology of nanosheets, specific surface area and kinds of cation between the nanosheets. Both H3O+-form samples showed high Eff(4) values are compared with Cs+-form layered titanate and the H+-form restacked titania nanosheets. This reveals that the H3O+ ions and the number of the active sites for ORR are related to the ORR activity The H3O+-R-E exhibited the best Eff(4) value (> 90%), which is comparable to that of a conventional 20 mass% Pt/C catalyst.

Under boiling and refluxing conditions for catalytic dehydrogenation of organic chemical hydrides (decalin, methylcyclohexane and others) in a batch-wise reactor, either suspended states with excess amounts of substrate or sand-bath states with its scarce amounts were found to be inferior generally to the so-called "liquid-film states" with adequate amount ratios of substrate to catalyst, where the catalyst-layer temperatures were superheated or raised higher than the boiling point, and, consequently, reactivities became more favorable at higher heating temperatures in contrast to the boiling suspended states. Equilibrium shifts due to reactive distillation were well demonstrated under boiling and refluxing conditions in naphthene dehydrogenation. Moreover, desorption of hydrogen from the active sites to the bubble space was enhanced in the superheated liquid-film states, with large translational entropy endowed. Provided the extents of equilibrium deviation were large enough (Prigogine's approach), thermodynamic couplings among irreversible processes would be realized between heat transfer and mass transfer as an example of the extended De Donder's equation. Restriction of chemical equilibrium could be removed under temperature gradient conditions, as the consequence that its Gibbs energy change became more negative than that under iso-temperature conditions. Within the framework of irreversible thermodynamics, the decreased retardation constant Kin the superheated liquid-film states was interpreted in terms of a vector-level coupling between temperature gradient and desorption. Moreover, vigorous bubble formation would give additional favor to the reaction rates owing to enlarged repeating frequencies of sequential non-microreversible processes in dehydrogenation catalysis. Organic chemical hydrides are attractive from the viewpoints of safe, economical, exergy-saving and large hydrogen contents for hydrogen storage and distribution. Their main defects have been pointed out hitherto that the endothermic reaction temperatures are too high. In this paper, a new concept on superheated liquid-film catalysis is explored for dehydrogenation temperatures to decrease, which would result in not only saving exergy for external heating but also avoiding catalyst deactivation due to carbon deposit. (C) 2007 Elsevier Ltd. All rights reserved.

Conductivity measurements at intermediate temperatures and phase studies were carried out in the compositions BaxCe1-yGdyO3-delta (0.8 <= 5x <= 5 1.1, 0 <= y <= 0.3) and BaxCe(0.8)Ln(0.2)O(3-delta) (x= 0.975, 1.0; Ln =Nd,Sm,Gd,DyYb). In Ba(x)Ce(0.8)Ln(0.2)O(3-delta), the Ba-deficient compositions (x=0.975) showed higher conductivity than the stoichiometric ones (x= 1.0) for all the Ln. The total (bulk) conductivities had a maximum (sigma = 5.5 x 10(-4) Scm(-1) at 250 degrees C) for Ln= Gd and x= 0.975. The sigma value was nearly two times higher than that of the known stoichiometric BaCe0.8Gd0.2O3-delta electrolyte and the best of those of known oxide ion conductors at intermediate temperatures. The Ba-deficient Ba0.975Ce0.8Gd0.2O3-delta composition was a single phase of the monoclinic perovskite-related phase (12/m). The high ionic conductivity is attributed to the fact that the Gd-doped composition had the largest cell volume in the Ln-doped Ba(0.975)Ce(0.8)Ln(0.2)O(3-delta) series. (C) 2007 Elsevier B.V All rights reserved.

To explore new electrocatalysts for alkaline direct alcohol fuel cells (ADAFCs), oxygen reduction reaction (ORR) activity of the pyrochlores Ln(2)Ru(2)O(7-delta) (LnR, Ln=Pr,Nd,Sm,Gd,Dy,Yb) and Ln(2)Ru(2-x)Mn(x)O(7-delta) (LnRMn(x), Ln=Pr,Nd) were examined in 0.1 M KOH solution at 70 degrees C. The onset potential (E-on) of the oxygen reduction current and the efficiency (Eff(4)) of 4-electron reduction of oxygen were evaluated by semi-steady state voltammetry with rotating ring-disk electrodes. In the LnR series, PrR with the highest ORR activity showed E-on = similar to 0.85 V vs. reversible hydrogen electrode and a Eff(4) value above 90 %. Their E-on and Eff(4) values revealed that LnR with a smaller atomic number had a higher ORR activity. This trend was in good agreement with that of electrical conductivities of the LnR. In addition, effects of Mn substitution for the Ru-site were confirmed in both PrRMnx and NdRMnx, series. Their ORR activities increased with an increase in the amount of Mn incorporation. The NdRMn0.25 exhibited the highest ORR activity (E-on = similar to 0.95 V and Eff(4) > 90%) in the formation range of the pyrochlore single phase. Moreover, the ORR selectivity was much higher than that of a conventional 20 mass% Pt/C catalyst: the E-on value was similar to 0.95 V even in 0.1 KOH containing 1 M methanol, ethanol, ethylene glycol and 2-propernol, whereas the E-on the value was similar to 0.7 V for the Pt/C catalyst.

A novel, low-cost proton-conducting semi-IPN has been successfully prepared from PVA/PAMPS blends by incorporating poly(ethylene glycol)bis(carboxymethyl)ether (PEGBCME) as a novel plasticizer. Although, the polymer is based on a relatively low content of PAMPS as a component of ion conducting sites, the resulting semi-IPN exhibited high proton conductivity (0.1 S cm(-1)) at 25 degrees C, which afforded a higher power density of 51 MW cm(-2) at 80 degrees C. A striking feature is that a long-term initial performance is achieved with a 130 h of stable fuel cell operation in DMFC mode due to effectively suppressed methanol crossover. This is a new record for a fully hydrocarbon membrane in DMFC, seeing that the PVA-PAMPS proton-conducting semi-IPNs are made simply of aliphatic skeletons. (c) 2007 Elsevier B.V. All rights reserved.

In order to clarify the mechanisms of proton transport in alcohol-penetrated perfluorosulfonated ionomer (PFSI) membranes for fuel cells, six membranes having different equivalent weight (EW) values were examined. Water, water/methanol mixture (molar ratio: 1/1), methanol, ethanol and 2-propanol were penetrated to each membrane, and membrane swelling, methanol permeability, proton conductivity and mass (alcohol and proton) diffusion coefficients were measured systematically. The methanol permeability Pm and the membrane expansion fraction theta showed that the PFSI membranes with smaller EW values were swelled larger by methanol and the permeation rates were also larger. The proton conductivity was reduced by methanol penetration into the membranes especially for the smaller EW value ones. To investigate the roles of CH(3) group of methanol, self-diffusion coefficients of the alkyl group Dcl 13 and of OH (including protons) DOH of alcohols (methanol, ethanol and 2-propanol) were measured separately by the pulsed-gradient spin-echo (PGSE) (1)H NMR method. Both D values increased with decreasing the EW value, and the D(OH) was always larger than the D(CH3). In addition, the differences between the DOH and D(CH3) increased with the decrease of the size of alkyl groups. These results indicate that protons transport faster than the alcohols by the Grotthuss (hopping) mechanism, and the faster proton transport was promoted more when the membrane was penetrated by smaller alcohol. The lipophilic nature of alcohols was found to be one of the factors that influence the mechanisms of proton transport in the membranes. (C) 2007 Elsevier B.V. All rights reserved.

This communication reports on the fabrication of membrane electrode assemblies (MEAs) for low temperature direct methanol fuel cells (DMFCs) using PVA-PAMPS proton-conducting semi-IPN membranes. New types of proton conducting polymers PAMPS, PVA/PAMPS and PVA/PAMPS/PEGDCE of similar chemical nature were tested as both the catalyst ink and the binder for MEA fabrications in place of traditional Nafion solutions. MEAs fabricated with PVA/PAMPS binder achieved not only the improved cell performance but also a good durability comparable to those fabricated with Nafion solution. Performance in DMFC mode with PVA/PAMPS/PEGDCE proton-conducting semi-IPN membrane showed a power density of 19.5 mW cm(-1) at 25 degrees C and increased to 49.7 mW cm(-2) at 80 degrees C with a metal loading on the anode of 2 mg cm(-2).

Oxide ion conductivity was examined in Ba(x)Ce(0.8)Ln(0.2)O(3-delta) (0.8 <= x <= 1.1; Ln=Lanthanoid). The slightly Ba-deficient compositions showed a higher conductivity than the nominal stoichiometric ones. A maximum total (bulk) conductivity (sigma=5.5x 10(-4) Scm(-1) at 250 degrees C, sigma=9.6x10(-3) Scm(-1) at 500 degrees C) was found in the Ba-deficient composition Ba0.975Ce0.8Gd0.2O3-delta. The a value at 250 degrees C was nearly two times higher than that of the known BaCe0.8Gd0.2O3-delta electrolyte. The conductivity is the best of those of known oxide ion conductors at intermediate temperatures. The non-stoichiometric Ba0.975Ce0.8Gd0.2O3-delta sample was a single phase of the monoclinic perovskite-related phase (I2/m). The high conductivity is attributed to the fact that the Gd-doped composition had the largest cell volume in the Ln-doped series. The unusual variation of the cell volume was due to a change in the portioning of the Ln ion between the B-site and the A(Ba)-site.

Vertically aligned carbon nanotubes (CNTs) were grown on a stainless steel substrate (SUS304) by resistance-heating method in alcohols containing homogeneously dissolved cobaltocene Co(C5H5)(2) as a catalyst source. Straight-chain primary alcohols, 1,2-ethanediol and cyclohexanol were used as carbon sources to examine the effects of the molecular structures on the morphology of the aligned CNTs. Methanol brought the best purity and alignment of CNTs of all the alcohols. The CNTs from 1,2-ethanediol was worse in the purity than those from ethanol with the same number of carbon atoms. The CNTs from cyclohexanol had a better purity than those from 1-hexanol. Distinctive features of this method are simple, low cost and a one-step process involving none of vacuum processes and catalyst preparation processes.

Oxide ion conductivity at intermediate temperatures of 25 degrees C-300 degrees C were examined in the system BaxCe1-yGdyO3-delta(0.8 <= x <= 1.1, 0 <= y <= 0.3). Their total (bulk) conductivities had a maximum of a =5.5 X 10(-4) Scm(-1) at 250 degrees C in the composition Ba0.975Ce0.8Gd0.2O3-delta. The a value was two times higher than that of the known BaCe0.8Gd0.2O3-delta (sigma=2.3 X 10(-4) Scm(-1) at 250 degrees C) and the best of those of known oxide ion conductors at intermediate temperatures. The non-stoichiometric Ba0.975Ce0.8Gd0.2O3-delta sample was a single phase of the monoclinic perovskite-related phase (I2/m).

Aligned carbon nanotube arrays (CNTAs) were readily synthesized by a resistance heating method on a substrate of commercially available stainless steel which has more plentiful availability than the wafers of Si and quarts. The catalyst was supported on the substrate by dip coating with a methanol solution of M(C5H5)(2)(M=Co,Fe), and the substrate was electrically heated at 800 degrees C in methanol. Highly aligned CNTAs were grown from the catalyst prepared from 0.02 M Co(C5H5)(2) methanol solution. The alignment was influenced by the concentration and the kind of M(C5H5)(2).

To clarify the transport mechanisms of alcohols and proton in perfluorosulfonated ionomer (PFSI) membranes for fuel cells, four membranes having different equivalent weight (EW) values were examined. Membranes were immersed in methanol, ethanol, and 2-propanol to prepare a total of 12 samples, and membrane swelling, mass (alcohol and proton) transports, and interactions between alcohols and proton were investigated systematically in the fully penetrated state. The membrane expansion fraction theta and alcohol content lambda increased with decreasing the EW value for all the samples. The self-diffusion coefficients (D's) of the alkyl group and\ of OH (including protons) were measured separately by the pulsed-gradient spin-echo (PGSE)-NMR method and the D's also increased with decreasing the EW value. These results implied that the alcohols penetrate into the hydrophilic regions of the PFSI membranes and diffuse through the space expanded by the alcohols. The ionic cluster regions formed by the alcohols resemble those induced by water in the water swollen membrane, where protons dissociated from sulfonic acid groups transport through the regions together with water molecules. The D values decreased with increasing the molecular weight of alcohols. This trend was supported by activation energies E-a estimated from the Arrhenius plots of D in the temperature range from 30 to -40 degrees C. The PGSE-NMR measurements also revealed that protons move faster than the alkyl groups in the membranes. The proton transport by the Grotthuss (hopping) mechanism was facilitated by the increase of the alcohol content and the decrease of the molecular weight. This result was also supported by the experimental results of proton conductivity kappa and mobility u(H+). Density functional theory (DFT) calculations of the interaction energy Delta E-int between proton and alcohol (including OH) showed that the vertical bar Delta E-int vertical bar increases with increasing the molecular weight of alcohols, which is in a inverse relationship with the kappa and u(H+) values. The proton transport depends strongly on the Delta E-int in the membranes.

In reformate-type polymer electrolyte fuel cells (PEFCs), CO tolerance of the anode catalysts is a central issue because CO inevitably comes out of the reformer and poisons very seriously the platinum-based catalysts. In this work, long desired novel-type CO-tolerant electrocatalysts have been developed from Pt and organic metal complexes (N,N-ethylenebis(salicylideneaminato) oxovanadium(IV) [abbreviated as VO(salen)] that are potentially superior to Pt-Ru and practically usable as such anode catalysts. These anode catalysts were tested for their CO tolerance using a half and a single fuel cell, at a cell temperature of 70 degrees C in the presence of 10, 50, and 100 ppm CO. The original metal complexes were mixed with the platinum precursor, platinum tetra-ammine chloride, and supported on the carbon black supporting material and heat-treated at various temperatures. The mixed catalysts Pt-VO(salen)/C revealed only little deterioration for less than 100 ppm CO, which was never attained by the state of the art alloy catalysts. The function of organic metal complex may originate during the heat treatment of catalyst preparation, and this suggests that the valence states of vanadium in Pt-VO(salen)/C play a role in manipulating the oxidation states of platinum. The catalysts were characterized using XRD, TEM, XPS, and XAFS techniques.

In order to investigate the influence of mixing organic metal complexes with various metal coordination structure on Pt/C catalyst for methanol oxidation reaction (MOR) in acidic media, N,N'-mono-8-quinolyl-o-phenylenediamine (mqph), N,N'-bis(anthranilidene)ethylenediamine (anthen) and N,N'-bis(salicylidene)ethylenediamine (salen), coordinating to Co(II) and Ni(II), wereexaminedas the model compounds. M(mqph), M(anthen) and M(salen) have MN3, MN4 and MN2O2 moiety as the catalytic active sites, respectively. Pt-M(complex)/C mixed catalysts were prepared by depositing the mixture of Pt tetra-ammine chloride and each organic metal complex with various mixing ratio (w/o) on graphite powder and then heat-treating at 600 degrees C in Ar atmosphere. The Pt-M(complex)/C samples were put on a glassy carbon disk electrode, and tested for electrochemical MOR in 1 mol dm(-3) CH3OH + 0.05 mol dm(-3) H2SO4 aqueous solutions at 25 degrees C. The mixed catalysts, especially Pt-Ni(mqph)/C and Pt-Co(mqph)/C, were found to enhance the MOR and exhibited higher catalytic activities than Pt/C, although each organic metal complex solely showed no catalytic activity. The catalytic ability was enhanced by mixing up to 50150 (Pt-M(complex)) mixing ratio for the Co(mqph) and up to 80/20 mixing ratio for the Ni(mqph). Larger amounts of M(complex) resulted in a decrease in the catalytic activities. These results indicate that the organic metal complexes, especially M(mqph), promote effectively the electrochemical MOR on Pt/C catalyst, the degree of which depends strongly on the ligand structure. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectra (XAS) for the Pt-M(complex)/C mixed catalysts showed that the metal coordination structures of organic metal complexes are partially retained on the graphite powder even after the severe heat-treatment at 600 degrees C in Ar atmosphere. Ab initio calculations for the organic metal complexes exhibited that the Ni metal site of the Ni(mqph) interact with OH- group more strongly than those of the other organic metal complexes. This fact suggests that the Pt-M(mqph)/C electro-oxidizes a byproduct CO absorbed on Pt by "bifunctional effect" in a similar way as Pt-Ru alloy catalysts do in promoting the effective electrochemical MOR. (c) 2006 Elsevier B.V. All rights reserved.

Multi-walled carbon nanotubes (MWCNTs) were synthesized from camphor by a chemical vapor deposition (CVD) method in a range of 750-900 degrees C. The catalyst was fed in three ways: (a) a sputtered Fe-film on a quartz substrate (b) vaporized ferrocene in an Ar flow; (c) both of (a) and (b). In the case (c), highly pure, dense and aligned MWCNT arrays formed on the quartz substrate at 850 degrees C, whereas nonaligned MWCNTs formed in the cases (a) and (b).

The locations and local environments of the Li ions in La0.56Li0.33TiO3 have been investigated by classical molecular dynamics (NID) simulations and first-principles (FP) calculations. The pair correlation functions of Li-O and Li-Ti indicate that the Li ions are located somewhat broadly mainly in the vicinity of the midpoint between the center of the A-site and the center of the bottleneck formed by four O2-. This is consistent well with that suggested from previous neutron diffraction and Li-6-NMR studies. The FP calculations suggest a different location of the Li ion in the vicinity of the midpoint between the centers of two adjcent bottlenecks; however it coincides with one of the locations shown by the trajectories simulated with the MD calculations.