Publisher：Materials Advances  

Ceramic proton-conducting electrolytes are highly appealing for large-scale hydrogen production via steam electrolysis at low to moderate temperatures. However, processing such electrolytes for industrial purposes poses several challenges. Our research demonstrates an effective tape-casting route that produces flat, planar BaZr<inf>0.44</inf>Ce<inf>0.36</inf>Y<inf>0.2</inf>O<inf>3−δ</inf> protonic half-cells with impressive dimensions of up to 50 mm × 50 mm. The cells are constructed using NiO-SrZr<inf>0.5</inf>Ce<inf>0.4</inf>Y<inf>0.1</inf>O<inf>3−δ</inf> as the fuel electrode, which ensures minimal warping and no cracks in the end-fired state. The electrolyte is dense and gas-tight after co-firing at 1300 °C and achieves a He leakage rate well within the threshold necessary for cell operation (∼5 × 10⁻⁵ hPa dm³ s⁻¹ cm²)⁻¹. Using B<inf>0.5</inf>La<inf>0.5</inf>CoO<inf>3−δ</inf> as the steam electrode, the cell achieves an electrolysis voltage of 1.3 V at a current density of 1.37 A cm⁻² at 600 °C. Moreover, they also exhibit high durability, lasting over 1000 hours of continuous hydrogen generation with no observable degradation, which is a testament to their reliability. In addition, scanning electron microscopy paired with energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray diffraction were employed to examine the structural changes in the half-cells after sintering at different temperatures. It is apparent from the latter techniques that upon sintering above 1350 °C, the electrolyte undergoes evident structural changes with new defects that affect the perovskite host. Finally, our work paves the way for the cost-effective fabrication of planar proton-conducting electrolysis cells.

DOI： 10.1039/d5ma00028a

Web of Science

Scopus

Publisher：Solid State Ionics  

Direct production of pressurized hydrogen through polymer exchange membrane (PEM) water electrolysis without the usage of the external compressor is an industrially important approach to maximize energy efficiency. An additional challenge in conventional water electrolyzers is the lack of separation of the generated gases, hydrogen and oxygen, from water. In this report, we demonstrate the operation of a new water electrolysis cell at high inlet water pressure with the assistance of a hydrophobic gas diffusion layer (hydrophobic-GDL). This configuration allows the gas/water separation to take place at the electrode so that pressurized water-free gases can be the output due to water being injected directly into the membrane as a source of electrolysis for a continuous supply of water it prevents membrane dehydration. Another important feature is also the cell can be operable in a reversible operation by combining with fuel cell operation. The membrane electrode assemblies (MEAs) were prepared using the hydrophobic-GDL, a Nafion membrane, and Pt-C/IrO<inf>2</inf> catalysts. Electrolysis experiments were performed at different temperatures with pressurized water (ΔP = 0.05–0.4 MPa based on atmospheric pressure) resulting output was pressurized (0.05–0.4 MPa) hydrogen and oxygen gases. The current densities at 1.6 V of electrolysis voltage were 117, 188, 262 mA cm⁻² at 25, 60, and 80 °C, respectively, and the hydrogen and oxygen gas evolution rates were consistent with theoretical values. It was found that increasing water pressure is beneficial to the electrode kinetics and there was an increase in water transport to the electrode surface as well as efficient gas separation and the production of pressurized gases.

DOI： 10.1016/j.ssi.2024.116678

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Scopus

Language：Japanese   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/denkikagaku.24-ot0304

CiNii Research

Publisher：Chemcatchem  

Electrolytic hydrogen production from water at neutral pH was achieved by using novel proton (H⁺) conduction system assisted by zeolite. Experimental and computational insights demonstrated that defective silanol nest generated by dealumination played an important role in the formation of water clusters and the H⁺ conduction over the zeolites proceeded via exchange of H-bonding between water molecules in the cluster. In addition, a proper balance between hydrophilicity and hydrophobicity is required for effective H⁺ conduction and silanol nest afford the balance. Furthermore, the contribution of hydrophilicity of the zeolite for the adsorption of water molecules became more drastic at high temperatures. Water electrolysis efficiency was strongly dependent on the H⁺ conductivity over the beta-type zeolite. The electrolytic cell containing the zeolite has the potential to be applied to the new hydrogen production system.

DOI： 10.1002/cctc.202301297

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Scopus

Publisher：Materialia  

Proton-conducting oxides are promising for applications in solid oxide fuel cells and steam electrolysis at intermediate temperatures (400–600 °C). The hydration reaction requires oxide ion vacancies and the protonic conductive species originate from this reaction. Increasing the proton concentration leads to higher proton conductivity but also expands the lattice volume, known as chemical expansion, which may lead to the mechanical failure of the oxide. Thus, it is important to clarify the factors that decrease the chemical expansion. A previous study suggested that chemical expansion could be suppressed by a large bulk modulus. Although this was only a qualitative argument, our study quantitatively clarifies the effect of the bulk modulus experimentally and theoretically. To examine the difference between Ce and Zr, which are typical elements in proton-conducting oxides, 6.25 mol% Y-doped SrZrO<inf>3</inf> and SrCeO<inf>3</inf> were prepared, and their bulk moduli were quantitatively evaluated. Y-doped SrZrO<inf>3</inf> had a larger bulk modulus than Y-doped SrCeO<inf>3</inf>. Our results support the previous finding that proton-conducting oxides with large bulk modulus suppress chemical expansion. In addition, our theoretical calculations of the force constants showed that the difference in bulk modulus was caused by the Zr-O bonds being more rigid than the Ce-O bonds. Our results should provide useful guidelines for suppressing chemical expansion in proton-conducting oxides.

DOI： 10.1016/j.mtla.2022.101616

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Scopus

Language：English   Publisher：The Electrochemical Society of Japan  

<p>The Sabatier reaction, which converts CO₂ and H₂ into CH₄ and H₂O (methanation), is an attractive way to produce a hydrogen carrier for renewable energy and CO₂ recycling. Also, for air revitalization in space missions, water electrolysis provides not only O₂, but also H₂, which can hydrogenate metabolic CO₂ from human respiration using the Sabatier reaction, producing H₂O for O₂ regeneration with the electrolysis. In this study, we have developed a three-dimensional finite element model of a test tandem cell combining a low-temperature Sabatier reactor working at around 220 °C with a proton exchange membrane water electrolyzer at around 120 °C. The model with our developed Sabatier reaction catalyst demonstrated that appropriate heat balance between the reactor and electrolyzer establishes a CO₂ conversion above 90 % and thermal self-sustainability. An appropriate thermal insulator between the reactor and electrolyzer maintains them at predetermined temperatures. The thermal analysis also shows thermal self-sustainability for a plurality of the tandem cells, simulating a cell in a stack. Exergy loss ascribed to the entropy production rate with the temperature drop between the Sabatier reactor and electrolyzer is also evaluated.</p>

DOI： 10.5796/electrochemistry.22-00035

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Scopus

CiNii Research

Publisher：Solid State Ionics  

Solid oxide protonic fuel cells are one of the most efficient means of directly converting stored chemical energy to usable electrical energy. Acceptor-doped Ba(Zr, Ce)O<inf>3</inf> perovskite-type oxides are the preferred electrolyte choice as they provide higher conductivity due to lower activation energy. While substantial progress has been made on small-sized protonic laboratory-scale cells, a considerable challenge has been upscaling robust planar-type devices. This paper employs a cost-effective inverse tape casting route and screen printing to fabricate flat planar anode-supported protonic fuel cells consisting of NiO-SrZr<inf>0.5</inf>Ce<inf>0.4</inf>Y<inf>0.1</inf>O<inf>3-δ</inf> substrate, SrZr<inf>0.5</inf>Ce<inf>0.4</inf>Y<inf>0.1</inf>O<inf>3-δ</inf> electrolyte, and BaCo<inf>0.4</inf>Fe<inf>0.4</inf>Zr<inf>0.1</inf>Y <inf>0.1</inf>O<inf>3-δ</inf> as the cathode. The processing parameters were analyzed and adjusted to obtain defect-free single cells of dimension up to 100 mm × 100 mm × 0.5 mm with diminished warping. In addition, the smooth tri-layered green tapes yielded suitably dense and gas-tight electrolyte layers after co-sintering at 1300 °C/5 h. Finally, the electrochemical performance of the 50 × 50 mm² SrZr<inf>0.5</inf>Ce<inf>0.4</inf>Y<inf>0.1</inf>O<inf>2.95</inf> based cells was evaluated, and their impedance spectra were deconvoluted to identify all performance-related polarization processes via the distribution of relaxation time.

DOI： 10.1016/j.ssi.2022.115918

Web of Science

Scopus

Publisher：Chemelectrochem  

Acceptor-doped barium zirconate cerate electrolytes constitute prospective materials for highly efficient and environmentally friendly electrochemical devices. This manuscript employs a systematic approach to further optimize ionic conductivity in Ba(Zr<inf>x</inf>Ce<inf>10−x</inf>)<inf>0.08</inf>Y<inf>0.2</inf>O<inf>3−δ</inf>, (1≤x≤9) oxides for moderate temperature electrolysis. We found two new composition variants by fixing a cerium/zirconium ratio of 5/4 at the perovskite B-site with incremental zirconium, an observation that contrasts many reports suggesting a linear decrease in conductivity with increasing zirconium. As a result, the composition BaZr<inf>0.44</inf>Ce<inf>0.36</inf>Y<inf>0.2</inf>O<inf>3−δ</inf> demonstrates a superior ionic conductivity (10.1 mS cm⁻¹ at 500 °C) to stability trade-off whereas, BaZr<inf>0.16</inf>Ce<inf>0.64</inf>Y<inf>0.2</inf>O<inf>3−δ</inf> exhibits the highest conductivity (11.5 mS cm⁻¹ at 500 °C) among the studied pellets. The high protonic conductivity is associated with a high degree of hydration, as confirmed by thermo-gravimetric analysis. In addition, both compositions as electrolytes allow successful hydrogen production in a steam electrolyzer prototype. Electrolysis voltage as low as 1.3 V is attainable at current densities of 600 and 500 mA/cm² respectively at 600 °C, achieving 82 % current efficiencies with the later electrolyte.

DOI： 10.1002/celc.202101663

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Scopus

Language：English   Publisher：The Electrochemical Society of Japan  

<p>A novel interdigitated flow field design for polymer electrolyte electrolysis cells (proton exchange membrane water electrolysis cells) composed of oxygen exhaust channels apart from liquid water feed channels has been developed for ground and space applications because the design is advantageous in terms of oxygen/water separation without buoyancy, and dispenses with water circulators for bubble removal in a cell and external separators by natural or centrifugal buoyancy. Finite element modeling of water transport in the polymer electrolyte (proton exchange) membrane in a cell with the interdigitated flow fields is conducted. Current-voltage (I–V) measurement of the cell is also performed for comparison with numerical modeling. Deviation of the experimental I–V characteristics from those of the numerical model indicates a possible water transport path in the in-plane direction of hydrophobic microporous layers (MPLs) coated on gas diffusion layers installed between the anode catalyst layers (CLs) and oxygen flow channels in the cell. Analysis of the deviation associated with the limitation of water transport also suggests fractional bubble coverage of produced oxygen gas at the CLs. The hydrophobic MPL acts to separate oxygen gas and pressurized liquid water due to the capillary pressure, while it determines the limitation of water transport to the CLs with the oxygen bubble coverage.</p>

DOI： 10.5796/electrochemistry.21-00097

Web of Science

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

In this work, we introduce a water electrolysis and CO2 hydrogenation tandem system which focuses on methane generation. The concept consists of a water electrolyzer thermally coupled to a CO2 hydrogenation reactor, where the power required to generate hydrogen comes from renewable energy.
A thermodynamic analysis of the tandem system was carried out. Our analysis exposes that it is possible to increase the exergy efficiency of the water electrolyzer and CO2 hydrogenation system by thermal coupling, where the thermal energy required to split water into H2 and O2 during the electrolysis process is compensated by the heat generated during the CO2 hydrogenation reaction. Here, the conditions at which high exergy efficiency can be achieved were identified.

Language：English   Publishing type：Research paper (scientific journal)  

In this work, p- and n-type Si pastes were prepared in a way by utilizing a planetary ball miller to pulverize Si source material. pn homojunction was formed by coating Si pastes onto metal substrates, followed by annealing under Ar or Ar + H 2 atmosphere. The optimal annealing temperature was found to be around 1050 °C that exhibits the lowest resistivity. A typical rectifying property of diode with small photovoltaic was observed for the device fabricated. It is anticipated that Si pastes could have potential for low cost device fabrication such as solar cells. All Cz Si ingot growth procedures could be skipped, consequently it is expected that the manufacturing cost for solar cell can be greatly reduced. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

DOI： 10.1007/s10854-019-00980-3

Language：English   Publishing type：Research paper (scientific journal)  

Aliovalent cation-doped perovskite-type oxides (ABO 3 ) exhibit proton conductivity originating from the hydration of oxide ion vacancies, which is accompanied by structural deformation, i.e. chemical expansion. The chemical expansion may lead to failure in electrochemical devices, and thus it is necessary to understand the causes of this process at the atomic scale. In this study, the chemical expansion behaviors of Y-doped strontium cerate and zirconate were comparatively investigated. High-temperature X-ray diffraction (HT-XRD) and thermogravimetric analysis (TGA) revealed that the cerate exhibits larger chemical expansion. Density Functional Theory (DFT) calculations revealed that this tendency can be accounted for by the different atomic distribution of the Y dopant between the cerate and zirconate, which results in differences in the size of the oxide ion vacancies to be hydrated as well as different elastic character. © 2019 Elsevier B.V.

DOI： 10.1016/j.ssi.2019.01.009

Language：English   Publishing type：Research paper (scientific journal)  

Heterointerfaces introduce unique localized defects into ionic conductors. This study explores the nanoionic characteristics exhibited by the proton-conducting oxides SrZr 0.9 Y 0.1 O 3-δ and SrCe 0.95 Yb 0.05 O 3-δ including finely dispersed precipitated platinum nanoparticles. The electrical conductivity of both the platinum-doped oxides revealed reversible nanoionic phenomena caused by the exsolution of the platinum in the form of platinum nanoparticles, at 0.5 vol% relative to the metal oxides, and dissolution in response to a change in gas atmosphere. In comparison with the original conductivity of SrZr 0.9 Y 0.1 O 3-δ and SrCe 0.95 Yb 0.05 O 3-δ , the conductivity of platinum-doped SrZr 0.9 Y 0.1 O 3-δ decreased significantly in a wet hydrogen atmosphere, whereas platinum-doped SrCe 0.95 Yb 0.05 O 3-δ showed almost no decrease in conductivity in the same atmosphere. The different responses of the two materials to the change in gas atmosphere are discussed in relation to the precipitation of platinum nanoparticles. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

DOI： 10.1007/s10008-018-04188-z

Language：English   Publishing type：Research paper (scientific journal)  

Ceramic proton conductors have the potential to become important components in future clean and efficient energy technologies. In this manuscript, barium cerium yttrium zirconate (Ba(Zr0.5Ce0.4)8/9Y0.2O2.9) and strontium cerium yttrium zirconate (SrZr0.5Ce0.4Y0.1O2.95), proton conducting perovskites were employed as solid oxide electrolysis cell (SOEC) electrolytes for hydrogen production via intermediate temperature steam electrolysis at 550 and 600 °C. Cathode-supported button cells examined for a 12 μm Ba(Zr0.5Ce0.4)8/9Y0.2O2.9 electrolyte, with Ni–SrZr0.5Ce0.4Y0.1O2.95 as the H2-electrode, and porous Ba0.5La0.5CoO3 as the anode reached current densities of 0.2 and 0.5 A cm−2 with applied voltage of 1.45 V, at 550 and 600 °C, respectively. Moreover, a hydrogen evolution rate of 127 μmol cm−2 per minute was achieved at 0.5 A cm−2, translating to a current efficiency of 82%. In addition, excellent cell performance was obtained using SrZr0.5Ce0.4Y0.1O2.95 as an electrolyte. Current densities of 0.2 and 0.5 A cm−2 were obtained at 600 °C with applied voltages of 1.28 and 1.63 V, achieving faradaic current efficiencies of 88 and 85%. The NiO–SrZr0.5Ce0.4Y0.1O3−δ composite cathode was more favorable for the densification of the supported Ba(Zr0.5Ce0.4)8/9Y0.2O2.9 electrolyte during sintering and could be promising for use as a cathode substrate in proton-conducting SOECs.

DOI： 10.1039/c8ta04019b

Language：English   Publishing type：Research paper (scientific journal)  

A water-absorbing porous electrolyte electrolysis cell is presented consisting of a hydrophobic gas diffusion layer (GDL), a controlled-hydrophobicity electrocatalyst layer, and a hydrophilic porous electrolyte layer. The specific character of this cell is that high-pressure water is injected directly into the porous electrolyte layer and is resisted by the electrocatalyst layer and GDL, which have strong water support force. In this study, the preparation method of the electrocatalyst layer and the porous inorganic electrolyte layer, and the evaluation of water electrolysis using the prepared layers were investigated. The optimized conditions and preparation methods of each layer of the MEA (i.e. the GDL, electrocatalyst layer, electrolyte layer) were determined. The assembly method and conditions of these three layers were also determined for fabricating MEAs for water electrolysis. The evaluation of water electrolysis tests using this MEA showed that the hydrogen evolution rate obeyed Faraday's Law in the low current density region (<10 mA cm−2).

DOI： 10.1016/j.ijhydene.2018.04.137

Language：English   Publishing type：Research paper (scientific journal)  

In this work, we investigate and compare the performance and cell polarization resistance of Ba0.5La0.5CoO3−δ (BLC) and double perovskite oxide BaGd0.8La0.2Co2O6−δ (BGLC) anode on cathode supported protonic steam electrolysis cells using a 20 μm SrZr0.5Ce0.4Y0.1O3−δ electrolyte with Ni-SZCY541 composite as the cathode. The kinetics of protons through the bulk and across the gas electrolyte interfaces of both anode materials were also studied by direct measurement of their tracer diffusions using time-of-flight secondary ion mass spectrometry depth profiling (TOF-SIMS). Cell terminal voltages of 1.74 and 1.93 V, were observed at a current density of 0.5 A cm−2 for both BLC and BGLC whereas a hydrogen evolution rate of 121.85 and 111.15 μmol cm−2 every minute was also obtained at the same current density, translating to a current efficiency of 78 and 72% respectively. Hydrogen tracer diffusion studies confirm BGLC can incorporate protons into the bulk relative to BLC even though the present steam electrolysis results show a better performance for BLC at 600 °C. © 2018 Elsevier B.V.

DOI： 10.1016/j.ssi.2018.02.016

Language：English   Publishing type：Research paper (scientific journal)  

In this study, organic-inorganic composite electrolyte membranes are developed for a novel water-absorbing porous electrolyte water electrolysis cell. As the materials of the composite electrolyte membrane, 80 wt% of a proton-con-ducting nano zeolite (H-MFI) as an electrolyte and 20 wt% of poly(vinyl alcohol) (PVA) as a cross-linkable matrix are used. The nano zeolite is prepared by a milling process. The nano zeolite-PVA composite membrane precursors are prepared by spraying onto a substrate, followed by cross-linking. The resulting nano zeolite-cross-linked PVA composite films are then evaluated for their properties such as proton conductivity as electrolyte membranes for the water-absorbing porous electrolyte water electrolysis cell. It is confirmed that conventional materials such as zeolites and PVA can be used for the water electrolysis as an electrolyte. © BME-PT.

DOI： 10.3144/expresspolymlett.2018.23

Language：English   Publishing type：Research paper (scientific journal)  

The characteristics of a water-absorbing porous electrolyte electrolysis cell, in which pressurized water is injected directly into the electrolyte layer, are investigated. High water support force is required for the gas diffusion layer (GDL) in this novel cell design, and therefore here we report a new type of hydrophobic GDL comprising an acetylene black (AB) and poly(tetrafluoroethylene) (PTFE) composite film. The method of preparation of the AB/PTFE slurry, film formation methods, and the AB/PTFE weight ratio were investigated and optimized. The ball-milling and transfer method were suitable for preparing uniform AB/PTFE slurry and successfully covering AB/PTFE film without any cracks on micro-porous layer coated carbon paper, respectively. An investigation about different PTFE weight ratios against AB from 0.1 to 6 showed a serious trade-off character between electrical resistance R, gas permeability V′, and water support force Plim. The 1/2.5 of AB/PTFE weight ratio was most optimal, which showed to have most equivalent R (2.5 Ω cm−2), V′(136 mL atm−1 cm−2 min−1), and Plim (0.25 MPa). We also confirmed that fabricated GDL with optimal condition was worked as the blocking layer against water injected through electrolyte layer and pressurized by nitrogen gas, and as gas-permeation layer for generated hydrogen gas in water electrolysis test.

DOI： 10.1016/j.ijhydene.2017.12.045

Language：English   Publishing type：Research paper (scientific journal)  

Some of the solid oxide materials, used in solid oxide fuel and electrolysis cells, are known to conduct protons once they are hydrated. However, the mechanisms by which solid oxide materials get hydrated is not clear. By performing detailed density functional theory calculations, we investigate hydration of two typical solid oxides with a single-crystal structure - a proton-conducting yttrium-doped strontium zirconate (SZY) and an oxide ion-conducting yttria-stabilized zirconia (YSZ). We suggest a four-step process to understand the hydration of solid oxides - water adsorption on the surface, proton migration from the surface to bulk, proton migration in the bulk, and oxide ion vacancy migration in the bulk. The hydroxide ion migration with a lower energy barrier, compared to the proton hopping mechanism, is proposed for the conduction of proton between the surface and subsurface of the perovskite oxide. Our analysis provides mechanistic insights into the hydration of single-crystal SZY and nonhydration of single-crystal YSZ. The study presented here not only explains the hydration of materials but also provides the importance of structural rearrangement when a proton is incorporated into the bulk of the solid oxide material. © 2017 American Chemical Society.

DOI： 10.1021/acs.chemmater.7b03476

Language：English   Publishing type：Research paper (scientific journal)  

The inuences of In- and Y-doping on the electrical conduction properties of barium zirconate were investigated. The electrical conductivity
measured on of BaZr1−x−yInxYyO3−δ (x= 0, 0.1, 0.2 and y= 0, 0.1, 0.2) could be understood that yttrium doping causes high bulk conductivity
and indium doping leads to lowering activation energy of the grain boundary. Co-doping of yttrium and indium promotes the enhancement
effect of improving the bulk conductivity and lowering of activation energy, and it is thus expected that the co-doping with yttrium
and indium can work for controlling the bulk and grain boundary conduction specically in the materials.

DOI： doi:10.2320/matertrans.MB201702

Language：English   Publishing type：Research paper (scientific journal)  

To enhance the power generation efficiency of solid oxide fuel cells (SOFCs), the use of proton-conducting solid solutions of doped BaCeO3 and doped BaZrO3, with formulas of the Ba(Zr0.1Ce0.7Y0.1X0.1)O3-δ (X = Ga, Sc, In, Yb, Gd), was investigated as SOFCs electrolyte materials with respect to both chemical stability and electrical conductivity. Regarding chemical stability, the weight changes of each material were measured under a CO2 atmosphere in a temperature range of 1200 °C-600 °C.Higher chemical stability was observed for dopant ions with smaller radii. Regarding conductivity, the dependences of the total conductivities on the oxygen partial pressure and temperature were measured in the temperature range of 600 °C-900 °C. In each material, the total conductivity was proportional to the oxygen partial pressure to the 1/4 power at high oxygen partial pressures, as previously observed for accepter-doped proton-conducting perovskite-type oxides. The derived conductivities for each type of charge carrier showed that the hole conductivity increased with the ionic conductivity. Based on the measured data, the leakage current densities were calculated for SOFCs with each of the investigated electrolyte materials and an area-specific resistance of 0.383 Ωcm2. BZCYSc showed the minimum leakage current density, with a value of 3.7% of the external current density at 600 °C. Therefore, this study indicates that BZCYSc is the most desirable among the materials investigated for use as SOFCs electrolyte. However, for BZCYSc to be used as SOFCs electrolyte material, a protective layer is needed to ensure its chemical stability. © 2017 Hydrogen Energy Publications LLC.

DOI： 10.1016/j.ijhydene.2017.04.267

Language：English   Publishing type：Research paper (scientific journal)  

The electrochemical properties of the proton-conducting ceramic fuel cells (PCFCs) with BaZr0.1Ce0.7Y0.1X0.1O3-δ (BZCYX, X = Ga, Sc, In, Yb, or Gd) electrolytes have been investigated. BZCYX materials were found to have various partial conductivities of charge-carriers such as ion, hole, and electron. The electrochemical properties exhibited strong dependences on operation conditions. When ASR and external current density were fixed at 0.4 Ω cm2 and 0.25 A cm-2, respectively, the electrical efficiency, η(X), was found to have the following sequential order: η(Sc) > η(In) > η(Ga) > η(Yb) > η(Gd). On the other hand, when ASR was not fixed but the thickness of the electrolyte was fixed at 25 μm, large variations appeared in the leakage current of the cells with the BZCYX electrolytes. The sequential order of the electrical efficiency with the fixed thickness was different from that with the fixed ASR as described in the above inequality expression, and depends on the operating temperature. The ratios of the leakage current with X = Yb or Gd were higher than those with X = Ga, Sc, or In. These high ratios were found to cause the serious drop in the electrical efficiency at an external current density of 0.25 A cm-2. We have successfully found out the candidates for the X element in BZCYX, by which high-efficient power generation would be expected. © The Electrochemical Society.

DOI： 10.1149/07801.0441ecst

Language：English   Publishing type：Research paper (scientific journal)  

Reforming of propane for the production of syngas can improve the utilisation of petroleumproducts in chemical
and energy processes as it is a major constituent in refinery gas. The search for catalytic and selective membranes
for the efficient conversion of natural gas with carbon higher than methane is very attractive and remains challenging.
Since Pr2Ni0.75Cu0.25Ga0.05O4 possesses high mixed conductivity and oxygen permeation properties, it is
extensively investigated for potential application for oxygen membrane reforming of propane in this study. The
membrane is coated with La0.5Sr0.5CoO3 and Ni catalysts to achieve surface activity for oxygen dissociation and
propane oxidation, respectively. The propane reforming efficiency of the membrane specimens with a 0.3 mm
thickness are studied as a function of temperature (800–1000 °C), using N2:C3H8:O2 reactant gases with three
mixing ratios of 90:7:3, 80:14:6 and 70:20:9 at flow rate of 50–375 ml/min. Over 99% of propane conversion is
achieved at every gas flow rate tested. The reaction products are H2, H2O, CO, CO2, CH4, C2H6, C2H4, C3H6, C4+,
and coke with the highest yield of CO and H2 (37 and 29%, respectively), are obtained at 900 °C using the gas
flow rate between 225 and 275 ml/min. The oxygen permeation rate observed at this condition is in the range
of 1600–1900 μmol/cm2/min. These results suggest that the utilisation of Pr2Ni0.75Cu0.25Ga0.05O4 is promising
as an oxygen membrane in the reforming of propane to syngas.

DOI： 10.1016/j.ssi.2016.12.035

Language：English   Publishing type：Research paper (scientific journal)  

The fundamental factors that influence the hydration of BaZrO3 (BZO) doped with trivalent cation M3+ (Al, Sc, Ga, Y, In, and Lu) for proton conductors were investigated by means of density functional theory calculations which take the configuration of complex defects into account. The creation of oxygen vacancies is favored for Al- and Ga-doped BZOs and leads to small hydration energies with stable proton sites at the nearest neighbor (1NN). Meanwhile, Y-, In-, and Lu-doped BZOs prefer protons at the second nearest neighbor (2NN). The stability of those defects can be formulated in the context of the energies of oxygen vacancy formation and hydration. BZOs with larger dopants gain more hydration energy by structural relaxation with protons located at 2NN. By isolating the associated complex defects, it is possible to increase the negative hydration energy, which in effect improves the degree of hydration of BZOs. © 2017 American Chemical Society.

DOI： 10.1021/acs.chemmater.6b03907

Language：English   Publishing type：Research paper (scientific journal)  

Previously, most studies of proton-conductive electrolytes for SOFCs were conducted to achieve lower-temperature operation. In this study, we investigate a proton-conductive electrolyte to realize high-efficiency SOFCs. To this end, the dependencies of the total conductivity of Ba(Zr0.1Ce0.7Y0.1Yb0.1)O3−δ on the oxygen partial pressure and temperature under wet and dry conditions were measured. Based on the measurement data, we analyzed the ratio of ionic current density to electronic current density in the temperature range of 550–900 °C. Assuming that the area-specific resistance of the electrolyte and the external current density were 0.383 Ω cm2 and 0.25 A cm−2, respectively, the leakage current densities caused by the minority carriers were calculated to be 5.4% and 9.7% of the external current density at 550 °C and 600 °C, respectively. This study developed a method to evaluate proton-conductive electrolyte materials and established guidelines for the development of new materials for high-efficiency SOFCs. © 2016 Hydrogen Energy Publications LLC

DOI： 10.1016/j.ijhydene.2016.07.265

Language：English  

Solid oxide fuel cells (SOFCs) are promising electrochemical devices that enable the highest fuel-to-electricity conversion efficiencies under high operating temperatures. The concept of multi-stage electrochemical oxidation using SOFCs has been proposed and studied over the past several decades for further improving the electrical efficiency. However, the improvement is limited by fuel dilution downstream of the fuel flow. Therefore, evolved technologies are required to achieve considerably higher electrical efficiencies. Here we present an innovative concept for a critically-high fuel-to-electricity conversion efficiency of up to 85% based on the lower heating value (LHV), in which a high-temperature multi-stage electrochemical oxidation is combined with a proton-conducting solid electrolyte. Switching a solid electrolyte material from a conventional oxide-ion conducting material to a proton-conducting material under the high-temperature multi-stage electrochemical oxidation mechanism has proven to be highly advantageous for the electrical efficiency. The DC efficiency of 85% (LHV) corresponds to a net AC efficiency of approximately 76% (LHV), where the net AC efficiency refers to the transmission-end AC efficiency. This evolved concept will yield a considerably higher efficiency with a much smaller generation capacity than the state-of-the-art several tens-of-MW-class most advanced combined cycle (MACC).

DOI： 10.1038/srep12640

Language：English  

The solid-state ceramic construction of SOFCs enables high fuel to electricity conversion efficiencies of as high as 50 to 60 percent LHV in high temperature operation, and allows more flexibility in fuel choice. In this study, we have developed a symbolic analysis method to investigate the availability of variable parameters appearing in multi-stage electrochemical oxidation mechanism that is expected to further improve the electric efficiencies of SOFCs. In the flow system of the multi-stage oxidation, the fuel utilization, Uf, at the most downstream stack, UfM, is expressed as a function of number of stacks, n, and total fuel utilization, UfT. When n = 10 and UfT = 85%, UfM is calculated to be 36%, which is much smaller than UfT. Therefore, if the most downstream stack has high robustness against lean fuel gas, UfT could be set to higher values without serious degradation by using this flow system. © The Electrochemical Society.

DOI： 10.1149/06801.1961ecst

Language：English   Publishing type：Research paper (scientific journal)  

In order to clarify the mixed effect of a cation on proton conduction, the electrical conductivity and the proton concentration of SrCe0.9 - xZrxY0.1O3 - δ (x = 0.0, 0.3, 0.5, 0.7, 0.9) were measured by the AC impedance method and thermogravimetric analysis at 573-1173 K. The electrical conductivity reached a maximum value at x = 0.5. The proton concentration at x = 0.5 is the highest at this experimental temperature. The condition of the oxygen vacancy was examined by a Raman spectroscopic analysis. The Raman band around 350 cm- 1 attributed to the CeO6 stretching mode was observed and the half band width of the peak is broad when the cation on the B site is a mixture of Ce4 + and Zr4 +. It was found that the symmetry of the octahedron around B-site might be reduced due to the cation mix on the B-site. © 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2015.01.010

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The effect of oxygen partial pressure on anode reaction of steam electrolysis using SrZr0.5Ce0.4Y0.1O3-α (SZCY-541) proton conducting electrolyte was investigated by AC impedance measurement in this work. The anode reaction was enhanced by increasing oxygen partial pressure, and this result was opposite to the expectation from the conventional anode reaction (water splitting reaction). The increase in the electrode reaction conductivity with oxygen chemical potential was proportional to PO21/4$$ {P_{{\mathrm{O}}_2}}^{1/4} $$ at 600 °C and at higher oxygen partial pressure region of 700 and 800 °C, suggesting the possibility that the enhancement is caused by the increase in hole concentration on the electrolyte surface near the anode. © 2015, Springer-Verlag Berlin Heidelberg.

DOI： 10.1007/s10008-015-2808-9

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The electrochemical properties of La0.9Sr0.1Yb0.8In0.2O3-δ (LSYbIn) were investigated by impedance measurements and the fuel cell performance test. The dominant charge carrier is the proton at low temperature. The hole is the dominant charge carrier in an oxidizing atmosphere at high temperature. Based on the conductivity data, the hydrogen potential profile and steady state current in the fuel cell at the polarized state were evaluated by calculation. The performance of the PCFC (protonic ceramic fuel cell) using LSYbIn as the electrolyte was examined in the temperature range of 873-1073 K. The maximum power density was 8.2 mW cm-2 at 1073 K. © 2014 Hydrogen Energy Publications, LLC. All rights reserved.

DOI： 10.1016/j.ijhydene.2014.06.113

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We developed a nano-structured Sm0.5Sr0.5CoO 3 (SSC55) cathode from slurry dispersed nanoparticles using a planetary bead-milling method. In order to evaluate the cathode performance, the cathode resistances and the protonic ceramic fuel cell properties were examined using electrochemical cells with a BaCe0.6Zr0.2Y 0.2O3 - δ electrolyte disk at intermediate temperatures. The cells with a milled SSC55 cathode showed lower cathode resistance and higher power density compared to those with the SSC55 cathode prepared from the conventional method. The improvement is attributed to an increase in the cathode reaction sites caused by the use of the smaller particles and a good adhesion to the electrolyte surface. © 2013 Published by Elsevier B.V.

DOI： 10.1016/j.ssi.2013.12.020

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In order to clarify the mixing effect of cation on the electrical conductivity and the hydration, the electrical conductivity of La 0.9Sr0.1(Yb1 - xMx)O 3 - δ (M = In, Y) has been determined by the four-probe AC technique in the temperature range of 673-1173 K. The proton concentration was estimated from the change in weight due to hydration by a thermogravimetric analysis. The conductivity and proton concentration increased with the increase in the In3 + content on the Yb-site. On the other hand, the electrical conductivity and protonic concentration of La0.9Sr 0.1(Yb1 - xYx)O3 - δ showed minimum values at x = 0.5. © 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2013.11.044

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Nano-structured La0.6Sr0.4Co0.2Fe 0.8O3-∞ (LSCF6428) cathode for protonic ceramic fuel cell (PCFC) prepared from planetary bead-milled nanoparticles was investigated. The cathode made by the bead-milled particles showed a porous structure consisting of homogeneous size particles and pores in the range 100 nm. The PCFC comprised of this cathode, Ni anode and BaCe0.6Zr 0.2Y0.2O3-∞ (BCZY622) electrolyte increased the cell performances about 6 times that of the cell using the cathode without milling. The cathode preparation using bead-milling is effective in improving the cell performance with an expanded contact area of the cathode/electrolyte interface due to decreasing particle size and good adhesion of the particles to the electrolyte. © 2014 The Japan Institute of Metals and Materials.

DOI： 10.2320/matertrans.M2013426

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In order to clarify the effect of the B site species in ABO3 perovskite oxides on the proton transport properties, the proton incorporation into a series of La0.9Sr0.1MO3-δ, (M = Al, Sc, In, Yb, Y) was studied by measuring the electrical conductivity and electromotive forces of the gas concentration cells, and by a thermogravimetric analysis. The proton concentration and electrical conductivity increased in the order of the B site species, Al < Y=Yb < Sc < In and Al < Y=Yb < In < Sc, respectively. La0.9Sr0.1AlO 3-δ showed an oxide ion conductivity, while La 0.9Sr0.1YbO3-δ and La 0.9Sr0.1YO3-δ exhibited a protonic conductivity in the temperature range of 573-1173 K. La0.9Sr 0.1ScO3-δ and La0.9Sr 0.1InO3-δ showed a protonic conductivity under 873 K, and a mixed proton and oxide ion conductivity at 1073 K. © 2014 Elsevier Ltd.

DOI： 10.1016/j.electacta.2014.01.113

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The electrochemical hydrogen pumping using Ba doped LaYbO3 oxide (La0.9Ba0.1YbO3-α, LBYb-91) was investigated in this work. It was found that LBYb-91 can conduct a large amount of protons as much as 100 mA cm-2 and the theoretical hydrogen evolution is actually occurred by the proton conduction. It was also found that LBYb-91 has high chemical stability against CO2 and H2O, and showed a comparable cell performance to SrZr0.9Y 0.1O3-α (SZY-91) with porous palladium electrode. The present study demonstrated that LBYb-91 is a potential candidate electrolyte material for the electrochemical cell to separate hydrogen from the reformed natural gas. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2013.03.05

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The proton transport properties of La0.9M0.1YbO 3-δ (M = Ba, Sr, Ca, Mg) were studied by the electrical conductivity measurement technique in the temperature range of 673-1173 K. The proton concentration was estimated by the weight changes due to the hydration reaction. The electrical conductivity and proton concentration of La 0.9Ba0.1YbO3-δ were the highest in La0.9M0.1YbO3-δ. The electromotive force of a hydrogen gas concentration cell using La0.9Ba 0.1YbO3-δ as the electrolyte was observed at 673-1073 K, and was in a good agreement with the theoretical values assuming that the proton transport number was unity. © 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.electacta.2013.01.156

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The change of the primary energy source from fossil fuels to the so-called renewable energies, such as solar and wind energy, is a major and necessary trend. The use of these energies needs efficient methods of energy storing and restoring, and hydrogen can serve for an effective conversion between the electricity and the chemical energy. This paper describes the ion-conducting materials applicable to the so-called "hydrogen energy system". Since hydrogen works as an energy medium in this system, hydrogen-ion-transporting materials are beneficial. Proton-conducting oxides will work for this purpose and will be introduced here, viewing from material designing and working mechanism. Application of the proton-conducting oxide materials to water electrolysis is another topic, and how the materials work in principle for conversion between electricity and chemical energy and how their performances could/can be improved will be described. © 2012 IUPAC.

DOI： 10.1351/PAC-CON-12-07-11

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The long-term stability in water was investigated for an inorganic proton conductor based on sulfated hydrous titania electrolyte in water electrolysis. Heat treatment temperature in the range of 400-700 °C during synthesis of the material was chosen as the critical parameter for the conductivity and stability in water. Electric resistance of the membrane electrode assembly using the sulfated hydrous titania in water and pH were investigated by the effect of heat treatment temperature on the stability of conductivity and acid detachment. TG, Fourier transform infrared spectroscopy, and energy-dispersive X-ray analysis measurements were performed to understand the amount and state of the sulfate groups on the surface of sulfated hydrous titania. Heat treatment at 650 °C was found to obtain good conduction behavior for the sulfated hydrous titania and was confirmed to work for a stable water electrolysis. © 2012 Springer-Verlag Berlin Heidelberg.

DOI： 10.1007/s10008-012-1793-5

Language：English   Publishing type：Research paper (international conference proceedings)  

NiFe oxide composite was studied as cathode of steam electrolysis cell using LaGaO 3 based oxide for electrolyte and it was found that H 2 formation rate at 1.6 V was much improved by combination of oxygen ion conducting oxide with NiFe (9:1) bimetallic alloy. In particular, a combination with La 0.6Sr 0.4Fe 0.9Mn 0.1O 3 (LSFM) or Ce 0.8Sm 0.2O 2 (SDC) is highly effective for increasing current density. Impedance plots for cathode consisted of two semicircles, which could be assigned to a diffusion and an activation overpotential in low and high frequency region, respectively. Compared with NiFe, mixing with SDC is much more effective for decreasing the diffusion overpotential. This might be assigned to increase in three phase boundary and porosity of cathode. © 2012 Elsevier B.V.

DOI： 10.1016/j.ssi.2012.02.052

Language：English  

Introduction of doped ceria interlayer to cathode/electrolyte interface of the electrochemical cell with proton conducting electrolyte was investigated using thin Ce 0.8Yb 0.2O 2-δ (YbDC) interlayer of about 500 nm thickness. YbDC interlayer conducted a large amount of protons as much as 170 mA cm -2. It was also found that cathode overpotential of the YbDC interlayer cells consistently showed a plateau at about 400 mV, at which that of the non-interlayer cells did not show, suggesting a possibility that cathode reaction is changed by introducing the doped ceria interlayer. This result also indicates that the interlayer showed high activity for cathode reaction when enough cathodic bias was applied. Especially, the interlayer showed high activity for the improvement of poor cathode reaction between SrZr 0.9Y 0.1O 3-α (SZY-91) electrolyte and platinum cathode. © 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.electacta.2012.04.102

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The proton conduction properties of sulfuric acidmodified nano-titania prepared by impregnation method were investigated. The proton conductivity of sulfuric acid-modified nano-titania was almost the same as that of hydrous sulfated nano-titania investigated in our previous work when the amount of adsorbed sulfate groups was almost the same. The highest conductivity was obtained at an adsorbed sulfate group amount of 0.42 mmol/g, not 0.97 mmol/g. This result indicates that the enhancement of conductivity with increasing amount of adsorbed sulfate groups is limited. This might be attributable to insufficient water molecule adsorption on the Ti 4+ site coordinated with a bidentate sulfate group due to the prevention by excess sulfuric acid.

DOI： 10.1007/s10008-011-1616-0

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A sulfonated nanotitania proton conductor based on hydrous titania was applied to water electrolysis as a hydrogen production method from electricity. Hydrous titania in the form of nanoparticles was used as a water absorbing porous electrolyte to allow water transport to the anode via electrolyte part of the water electrolysis cell. Overpotential of the porous electrolyte cell in water was lower than that of the Nafion 117 membrane. Evolution of hydrogen and oxygen by electrolysis were confirmed although the rates of gas evolution were smaller than those calculated from Faraday's law. © The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.80.246

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The single-nanosizing of a ceramics by a topdown method was demonstrated using a "wet planetary bead-milling" method, which is the combination of bead milling and planetary milling. By using the planetary bead-milling, single-nanoparticles (about 2 nm) of BaZr 0.9Y 0.1O 3-α (BZY-91), which is one of the perovskite type oxides, was obtained with the combination of 0.05mmφ zirconia beads as pulverization media and ethanol as dispersion media. © 2012 The Ceramic Society of Japan.

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The electrical conductivities of SrZr0.9Y0.1O 3-δ (SZY10) and BaCe0.95Y0.05O 3-δ(BCY5) were measured as a function of hydrogen partial pressure P(H2), oxygen partial pressure P(O2), steam partial pressure P(H2O) and temperature. Their relaxation processes were analyzed using the solution of Fick's diffusion equation to determine the chemical diffusion coefficients and surface reaction rate constants. There were the differences in chemical relaxation kinetics and the conductivity dependence on P(H2O) between the both oxides. The chemical diffusion coefficients depend on temperature but are essentially independent of P(H 2), P(O2) and P(H2O). The ambipolar diffusion treatment can explain the temperature dependence of chemical diffusion coefficients quantitatively. The chemical diffusion coefficients of SZY10 is one or two order of magnitude smaller than those of BCY5 at low temperature. The sluggish conductivity relaxation in SZY10 was due to considerably small oxygen vacancy diffusion coefficients at low temperatures. The total conductivity depends on P(H2O) in the case of SZY10, but not for BCY5. This different dependence on P(H2O) is caused by the difference in the ratio between proton mobility and oxide-ion mobility. © 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2010.03.011

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Effects of transition metal dopant to Ti site in Sr3Ti 2-xMxO7 (M = Fe, Ga, Co) on the electrical conductivity and the oxygen permeation property were investigated. Among the examined dopants, it was found that doping Co is the most effective for improving the electrical conductivity and the oxygen permeation rate. With increasing Co amount, electrical conductivity and oxygen permeation rate monotonically increased and the highest oxygen permeation rate is achieved at Sr3Ti0.8Co1.2O7 among the Co doped sample. On this composition, the oxygen permeation rate from air to He is achieved a value of 2.02 cc/min.cm2 at 1273 K. © 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2010.04.018

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vol. 182, pp. 13-18

DOI： 10.1016/j.ssi.2010.11.016

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N2 yield on Ba0.8La0.2Mn 0.8Mg0.2O3 decreased from 70% to 30% on the addition of 1% CO2, which is a much larger negative effect than that seen with O2. The CO2 negative effects are not permanent and this may result from the inhibition of NO adsorption. Co-feeding of H 2 as a reductant is effective for increasing NO conversion. This suggests that the catalyst surface was covered with strongly adsorbed nitrate or nitride species which formed by adsorption of NO on oxygen formed by the decomposition of NO, and the removal of this surface species might be the most important step for the NO decomposition reaction. Co-feeding of H2 is also effective for increasing the NO decomposition activity in the presence of CO2. The reaction mechanism was studied by IR measurements which also revealed that the surface of the catalyst was covered with strongly bound nitrate species (NO3 -). The addition of H2 to the reaction mixture is effective for NO3 - removal and so accelerates the NO decomposition under coexistence of CO2. © 2008 The Chemical Society of Japan.

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Pressure effects on the water electrolysis performance of the cell using Nafion 117 for electrolyte were investigated. It was found that the internal resistance of the cell decreased with increasing the pressure, while it is expected that the chemical equilibrium shifts to the reactant side. Detail analysis of the internal resistance by a current interruption method suggests that decrease in the internal resistance results from the decreased IR loss, which is assigned to the increased conductivity of Nafion 117 film. On the other hand, the overpotential of cathode and anode slightly increases as the pressure increases. In particular, the concentration overpotential on both electrodes increased under an elevated pressure. Since the internal resistance decreased by elevating water pressure, water electrolysis efficiency was improved to a value of 65% at 20 MPa, 100 mA/cm2. Consequently, this study reveals that pressure shows the prospective effects on the water electrolysis performance of the cell using Nafion 177 electrolyte in an initial short period.

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We developed a novel technique to investigate local pH distribution on a chip using patterned hydrogel film made of UV photosensitive resin. The hydrogel is first patterned by photolithography in any shape on a glass, and later functionalized with the pH indicator, for example, Bromocresol Green (BCG). The hydrogel is polymerized by UV-ray illumination (300-400 nm) on the glass substrate, which is spin coated with the water-soluble prepolymer solution, and immobilized on the glass surface. Unexposed part can be removed easily by water. The hydrogel is hydrophilic, transparent, biocompatible, and is impregnated with the BCG. Then, the Polydimethylsiloxane (PDMS) microchannel is assembled and bonded on the functionalize surface. In this way, we can make patterned pH sensitive surface in the microchannel. Local pH is measured from the color of the hydrogel impregnated with BCG based on the calibrated color information in YCrCb color space. We succeeded in measuring local pH distribution in the microchip. ©2008 IEEE.

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A metal substrate with structure-controlled nanopores was prepared by the thermal reduction method based on the phase diagram and the nanocomposites for the substrate of solid oxide fuel cells (SOFCs). The few-micrometers-thick LaGa O3 -based oxide film was deposited with the laser ablation method. The fabricated thin-film SOFC on the metallic substrate demonstrates a startup within 5 min and generates electric power with high power density: 0.95 W cm2 at 873 K and 0.1 W cm2 at 673 K. © 2007 The Electrochemical Society.

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High-temperature proton conductors are oxides in which low-valence cations are doped as electron acceptors; the incorporation of water molecules into the oxides results in the formation of protonic defects that act as charge carriers. Since the protons thus formed are in equilibrium with other electronic defects, electrons and holes, the oxides possibly have different proton-conduction properties at and near boundaries when they are in contact with another phase. In this paper, we present our recent experimental observation of a marked change in the electrical properties of a proton conductor upon the dispersal of fine platinum particles in the oxide. First, the material shows extremely low electrical conductivity in comparison with the original proton-conducting perovskite. Second, there was a threshold amount of platinum at which such a drop in conductivity occurred. A percolation model is employed to explain these experimental results; the fine platinum particles dispersed in the proton-conducting oxide wears highly resistive skin that is formed due to shifts in defect equilibriums, which prevents ionic/electronic conduction. The experiments suggest that the ion-conducting properties of oxides can be varied by introducing interfaces at a certain density; nanoionics is a key to yielding enhanced and/or controlled ionic conduction in solids. © 2007 NIMS and Elsevier Ltd.

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The effect of transition metal (Mn, Fe and Co) doping to the Ce-site of the perovskite-type protonic conductor BaCe0.90Y0.10O 3-δ was examined. Single-phase samples of BaCe 0.90-xY0.10MxO3-δ were obtained at 0 ≤ x ≤ 0.10 for M = Mn and Co and at 0 ≤ x ≤ 0.075 for M = Fe. The conductivity of the samples in air decreased with transition-metal doping. Among the doped samples, Mn-doped solutions showed the lowest conductivity and the highest activation energy of conduction. The conductivity of these samples was independent of the concentration of the transition metals (x). This behavior of the conductivity could be explained by supposing the generation of the impurity state by transition-metal doping inside the band gap. In hydrogen, samples showed ionic conduction. The influence of transition-metal doping on the conduction behavior in hydrogen is small. © 2005 Elsevier B.V. All rights reserved.

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The electronic structure of the protonic conductor Y-doped BaCeO 3 (BaCe0.90Y0.10O3-δ) has been studied by soft-X-ray spectroscopy. The valence band of H 2-annealed BaCe0.90Y0.10O3-δ, which consists of the O 2p states hybridized with Ce 4f states, shifts to the higher binding energy side by approximately 0.4 eV. In the air-annealed BaCe0.90Y0.10O3-δ, holes and acceptor levels are observed at the top of the valence band and just above E F, respectively. Their intensities are lower in H 2-annealed BaCe0.90Y0.10O3-δ. These findings indicate directly that hydrogen doping compensates for the presence of the holes. © 2005 Elsevier B.V. All rights reserved.

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The high-temperature characteristics of donor-doped SrTiO 3/indium tin oxide (ITO) Schottky solar cells were investigated by current-voltage and impedance analyses at various oxygen partial pressures (PO2) (1-10-4 bar) at 873 K. Both current-voltage and impedance characteristics showed a reversible oxygen partial pressure dependence. The junctions demonstrated the photovoltaic effect even at high temperatures, which means the nonohmic behavior of the heterojunction remains even at high temperatures. The highest open circuit voltage and short circuit current density were 123 mV and 1.37 mA cm-2, respectively, at 1 bar O2 under 261 mW cm-2 UV irradiation. Incident photon-to-current conversion efficiency and energy conversion efficiency improved as PO2 increased. The influence of oxygen partial pressure on the solar cell characteristics is discussed. © 2005 The Japan Society of Applied Physics.

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The electronic structure of protonic conductor SrZr1-xM xO3-δ (M = Y3+, Sc3+) has been studied by soft-X-ray spectroscopy. The valence band is mainly composed of O 2p state. The conduction band is composed of Zr 4d state. The holes and the acceptor level are observed at the top of valence band and just above the Fermi level (EF), respectively. In H2-annealed SrZr 1-xMxO3-δ (M = Y3+, Sc 3+), their intensities decrease and the hydrogen-induced level is created at just below EF. The energy separation between the bottom of the hydrogen-induced level and the top of valence band agrees with the activation energy estimated from the electrical conductivity. © 2005 Elsevier B.V. All rights reserved.

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Polarization modulated infrared reflection absorption spectroscopy (PM-IRRAS), which is one of the advanced FT-IR methods, was combined with conventional electrochemical techniques for in situ observation of high temperature electrode reactions at 773 K in oxygen partial pressure of 3 × 104 Pa. PM-IRRAS method can detect surface species selectively with high sensitivity at high temperatures without background measurement to cancel the infrared absorption by gas phase. Two different O2(g), Pt/YSZ electrochemical half cells were prepared as simple models of gas-electrodes. One of them had a working electrode which was composed of uniformly distributed platinum; the other had an island-networked platinum electrode. On the former electrode, PM-IRRAS detected a concentration change of adsorbed oxygen on Pt electrode with controlled cathodic overpotential. On the other hand, for the latter sample that showed smaller cathodic current, the signal of the adsorbed oxygen was suppressed by SiO2 impurity, whose spectrum was detected at 1220 cm- 1 by PM-IRRAS. It was shown that PM-IRRAS gives useful information on the state of adsorbed species which affect the electrode kinetics and the cell performance. © 2005 Elsevier B.V. All rights reserved.

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Perovskite-type oxide, La0.5Sr0.5CoO 3-δ, has large oxygen nonstoichiometry and high electrical conductivity with a large carrier concentration. The oxygen nonstoichiometry, δ, of dense La0.5Sr0.5CoO3-δ was measured in the stream of NOx-O2-N2 system at 873 to 1073 K by means of a thermogravimetric method. Small amounts of NO 2 caused large changes in oxygen nonstoichiometry. It seems probable that excessive amounts of oxygen can be incorporated into the bulk due to catalytic decomposition of NO2, and as a result, oxygen potential on the surface of the sample seems to be much higher than that of gaseous phase. EMF measurements for dense La0.6Sr0.4CoO 3-δ electrode also revealed that the oxygen potential is affected by NO2. Thus, the gas sensing mechanism of this oxide was found to relate to the change of the bulk property, especially oxygen nonstoichiometry. © 2005 Elsevier B.V. All rights reserved.

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DOI： 10.1149/1.2041333

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DOI： 10.1149/1.1943568

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Oxide ion conductivity in La(Sr)Ga(Fe,Mg)O3 was investigated in this study and it was found that the oxide ion conductivity much improved by doping Fe into Ga site. Although the electrical conductivity monotonically increased with increasing amount of Fe, partial electronic conduction became significant. Considering the transport number of oxide ions and conductivity, the optimum composition for oxide ion conductivity in this system is La 0.7Sr0.3Ga0.7Fe0.2Mg 0.1O3-δ (LSGFM73721). Although transport number of oxide ions is almost 0.8, extremely high power density was achieved by using LSGFM73721 as electrolyte of a SOFC. The maximum power densities of 870 and 167 mW/cm2 were obtained at 1073 and 873 K, respectively, in spite of 0.5 mm thickness when 90Ni10Fe was used for the anode. A coating of La 0.9Sr0.1Ga0.8Mg0.2O3 film on anode side of LSGFM plate was investigated by pulsed laser ablation method. Since the deposited film was not dense, open circuit potential was almost unchanged in spite of LSGM film deposition, however, power density improved much by deposition of LSGM film and the maximum power densities of 197 and 100 mW/cm2 were achieved at 873 and 773 K respectively. This study reveals that LSGMF is a suitable electrolyte for intermediate temperature SOFCs.

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DOI： 10.1149/1.2032407

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For LaMnO3+δ with oxygen-excess nonstoichiometry, in situ X-ray diffractometry was performed under high temperatures and precisely controlled oxygen partial pressures, PO2. A rhombohedral phase was observed under most experimental conditions. With temperature rising, the lattice volume increased linearly in a low temperature region; the coefficient of linear thermal expansion (CTE) was 1.06×10-5K-1. In a high temperature region, the temperature dependence of the lattice volume upwardly deviated from the linearity, indicating that the unit cell expanded upon decrease in excess oxygen. The nonstoichiometry coefficient of the linear isothermal expansion was calculated at 5×10-2 using literature data on δ(T, PO2). The rhombohedral distortion escalated with temperature and PO2 decreasing. The dependence of cell volume and distortion on nonstoichiometry is well interpreted as the effect of variation in the ionic radius and tolerance factor. © 2004 Elsevier B.V. All rights reserved.

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The influence of water vapor pressure, P(H2O), on chemical stability of SrCe0.95Yb0.05O3-α under hydrogen atmosphere was investigated using XRD and Raman spectroscopy. From an XRD study, a second phase assigned to Sr2CeO4 was observed under strongly reducing conditions such as dry H2 with P(H2O)=4.6 × 10 Pa [ P(O2)=3.1 × 10 -15 Pa] at 1273 K. From Raman spectroscopy, it was found that treated specimens under hydrogen atmosphere exhibited additional Raman bands, which may be assigned to the second phase. The relative intensity of the additional Raman band at 460 cm-1 drastically increased with decreasing P(H2O) in the region P(H 2O)<7.0×102 Pa (2°C sat.), whereas it was quite low in the region P(H2O)>7.0×102 Pa [P(O2)>3.0×10-14 Pa] at 1273 K. The perovskite phase proved to be stable against hydrogen with an increase in P(H2O) or a decrease in temperature. © 2004 Elsevier B.V. All rights reserved.

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The electrical conductivity of Ce0.992Nb0.008O 2-δ was measured as a function of oxygen partial pressure between 10-28 and 1 bar in the temperature range of 873-1173 K. The activation energy for the conductivity at an oxygen partial pressure of 10 -4 bar was 0.29 eV. This value was too small to be assigned for oxide ion conduction, indicating that, in oxidizing atmospheres, electronic conduction is dominant due to Nb doping. On the other hand, the oxygen partial pressure dependence of conductivity was complicated in reducing atmospheres. Defect chemical analysis was made to interpret the conductivity variation with oxygen partial pressure. The defect association model was introduced, which assumes that oxygen vacancies are easily formed around niobium ions and that one of the released electrons is trapped on Nb5+. The experimental data was found in accordance with that calculated by the proposed defect association model. © 2004 Elsevier B.V. All rights reserved.

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The oxygen nonstoichiometry, δ, of La1-xCa xCrO3-δ (x=0.1-0.3) was measured by means of thermogravimetry as a function of oxygen partial pressure, P(O2), temperature, T, between 1073 and 1373 K, and the content of calcium, x. In any compositions, δ becomes larger and is getting closer to δ=x/2 with decreasing P(O2). At the same P(O2), δ of La 1-xCaxCiO3-δ increases with increasing T and x. There is almost no difference in oxygen nonstoichiometry between Ca-doped lanthanum chromite and Sr-doped lanthanum chromite. Defect chemical analysis was performed taking defect interaction into consideration. The nonstoichiometry curves were reproduced well by the proposed defect model and the obtained thermodynamic parameters. The influence of defect interaction on defect formation energy can be mainly attributed to change in interatomic potential due to defect-induced lattice expansion. © 2004 Elsevier B.V. All rights reserved.

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High temperature photovoltaic effects at the Nb doped SrTiO3 (STNO) / Indium Tin Oxide (ITO) interface were investigated. The STNO/ITO interface was prepared by Pulsed Laser Deposition Technique (PLD) on 0.01 wt% Nb doped SrTiO3 single crystal (100) at 873 K in 1 Pa O2 condition. A depletion layer of Schottky barrier formed at the STNO/ITO interface was irradiated with UV-light, the wavelength of which corresponds to the band gap of STNO at high temperatures (673-873K). The current-voltage (I-V) characteristics were measured at temperatures up to 873K in various oxygen partial pressures. It was found that the STNO/TTO interface shows rectification and photovoltaic effects at the temperatures studied, which vary with oxygen partial pressure. These phenomena ensure the existence of Schottky barriers at high temperatures and the possibility of high-temperature photovoltaic energy conversion.

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The electronic structure in the band-gap region of protonic conductor SrZr0.90Y0.10O3-δ was studied by soft-X-ray absorption spectroscopy (XAS). The O 1s XAS spectrum of air-annealed SrZr0.90Y0.10O3-δ exhibits three distinct features, namely, the holes on top of the valence band, acceptor-induced level just above the Fermi level and Zr 4d defect-induced level at the bottom of the conduction band, which are lower in the O 1s XAS spectrum of wet-annealed SrZr0.90Y0.10O3-δ. These findings directly indicate that the doped hydrogen compensates the presence of the holes.

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Metal or oxide electrodes (Pt, Au, Ag, (La, Sr)CoO3) were deposited on single crystals of 0.02 mol% Nb doped SrTiO3 by pulsed laser deposition. Current-voltage and capacitance-voltage responses were measured using three-terminal electrode configuration. Under high oxygen partial pressures, clear rectification behaviors were observed. Diffusion model well explained the current vs. voltage relationship with ideality factors close to unity. The barrier height varied reversibly with oxygen partial pressure, and was almost independent of the electrode materials, which suggested that the Fermi level at the interface was pinned by the surface states. The origin of the surface states was discussed in terms of oxygen adsorption or oxidative formation of metal vacancies around the surface. Chemical interaction between the surface and oxygen and resulting cation rearrangement was concluded to play an important role from the long stabilization time on oxygen partial pressure change. The water vapor pressure dependence of the barrier height was also explained by competitive adsorption of oxygen and water. © 2004 Kluwer Academic Publishers.

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Carbon deposition on a SOFC anode was investigated under direct hydrocarbon fueling condition. Microscopic behaviors were observed with a newly designed sample holder that enabled in-situ observation of an electrode in operation under controlled atmosphere at elevated temperatures. The preferential carbon deposition site, the structure of the deposited carbon, and the chemical or electrochemical re-oxidation processes were investigated with an optical microscope combined with a laser Raman microscope. Color and morphology change of the electrode surface was recorded with a CCD camera, and the deposited materials were identified with a laser Raman microscope. A nickel micro grid was used as a model electrode of a well-defined microstructure. When the cell was kept at an open circuit condition in methane, carbon started to deposit on the surface of Ni grid electrode. The deposition of carbon was clearly observed as the change in the reflection on the nickel surface by optical microscope as well as by the appearance of the specific peak at ∼1560 cm-1 in Raman spectroscopy. The deposited carbon was in the form of graphite on the nickel grid electrode. The carbon coverage on the surface was not uniform but varied from grain to grain. When a certain anodic overpotential (e.g. 200 mV) was applied to the electrode, the carbon disappeared gradually from the edge of the electrode i.e. from the electrode/electrolyte boundary where oxygen was supplied electrochemically. It is the first in-situ observation of the electrochemical carbon oxidation in a real operation condition.

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The electronic structure of the protonic conductor Y-doped BaCeO 3 (BaCe0.90Y0.10O3-δ) has been studied by photoemission spectroscopy and X-ray absorption spectroscopy. The Fermi level (EF) of H2-annealed BaCe0.90Y 0.10O3-δ shifts to the conduction band side by approximately 0.4 eV. The holes and acceptor level are observed at the top of the valence band and just above EF, respectively. Their intensities are lower in the H2-annealed BaCe0.90Y 0.10O3-δ, indicating that doped hydrogen enters hole and acceptor states. These findings indicate that the electronic structure of the protonic conductor BaCe0.90Y0.10O3-δ obeys the rigid-band model.

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Raman spectra of Yb-doped strontium cerate SrCe1-xYb xO3-δ were measured to evaluate their defect structure, which is much expected to influence their physical properties, such as solubility and diffusivity of protons in these oxides. In spectra, a signal showing existence of oxygen vacancies was observed at about 630 cm-1 for doped samples. The intensity of this band increased with oxygen vacancy formation by Yb-doping and by annealing at high temperatures in dry [low P(H2O)] or reducing [low P(O2)] conditions. Since a clear relationship between a peak intensity of the oxygen vacancy band and dopant concentration was obtained, it was found oxygen nonstoichiometry in SrCe 1-xYbxO3-δ system could be evaluated using this relationship. © 2003 Elsevier B.V. All rights reserved.

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The electromotive force (EMF) behavior of the hydrogen isotope cell using high-temperature proton conductors has been investigated. In the present study, the EMFs for H2-D2 mixtures and those for H 2-D2 mixtures diluted with argon against the H 2 and D2 reference gases were measured for an electrochemical cell using a proton-conducting electrolyte of CaZr 0.90In0.10O3-α. The theoretical equation for the hydrogen isotope cell was derived and compared to the measured EMFs to confirm its validity. The EMF of the cell can determine the atomic molar fraction of the hydrogen isotopes for gases in which the total pressures of the hydrogen isotopes are known. © 2003 Elsevier B.V. All rights reserved.

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An electrochemical hydrogen pump using the SrCe0.95Yb0.05O3-α proton conductor has been applied to hydrogen extraction and production. The extraction of hydrogen from dilute hydrogen and synthesis gases, and hydrogen production by water vapor electrolysis are demonstrated. The extraction of hydrogen could be operated with a current efficiency close to unity, while some electronic conduction appeared in the water vapor electrolysis. The introduction of water vapor into the cathode compartment was effective to extend the current density. These results, together with the problems to be solved, are mainly discussed in terms of electrode reactions and ionic transport numbers. © 2002 Elsevier Science B.V. All rights reserved.

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The conduction behavior of rhodium-doped AZrO3 (A=Ba, Sr and Ca) was investigated using electrical and electrochemical methods at elevated temperatures. The protonic conductivity of the Rh-doped AZrO3 in hydrogen was close to that of the Y-doped AZrO3. The transport numbers of the ions in hydrogen were unity in all the samples examined in this study. Under high-oxygen partial pressures, the conductivities of the Rh-doped AZrO3 were lower than those of the Y- or In-doped AZrO3, suggesting the low conductivity of electron holes. The oxygen partial pressure dependence of the conductivity indicates that a change in the valence of the rhodium ion might suppress the generation of mobile holes under a high-oxygen partial pressure condition. © 2002 Elsevier Science B.V. All rights reserved.

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An electrochemical sensor of hydrogen isotopes based on solid electrolytes for determining the hydrogen isotope ratios and/or total hydrogen pressures in gases has been developed. This paper describes the methodology of the hydrogen isotope sensing together with experimental results. When hydrogen isotope gases are introduced to an electrochemical cell using a proton-conducting electrolyte (hydrogen isotope cell), the electromotive force (EMF) of the cell agrees with that theoretically estimated. The EMF signals can be used for the determination of the hydrogen isotope ratio in gases if the total hydrogen pressure is predetermined. By supplementary use of an oxide ion conductor cell, both the ratio and total pressure of the hydrogen isotopes can be simultaneously determined.

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In the electrochemical hydrogen pump based on SrCe0.95Yb0.05O3-α proton conductor cell, effects of water vapor supplied to the cathode and operation temperature on the pumping characteristics were examined. Hydrogen-pumping capacity could be enhanced by increasing water vapor supply to the cathode and by reducing operation temperature within the examined range of 700-900°C. Presence of sufficient water vapor at the cathode would keep the current efficiency of the hydrogen pump. © 2001 Elsevier Science B.V. All rights reserved.

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The electronic and ionic conduction behavior of Ru-doped SrTiO3 at high temperature was investigated. The conductivity increased significantly with increasing Ru content. SrTi0.80Ru0.20O3-δ exhibits fairly high conductivities, e.g., 3 S cm-1 at 1000°C, and 2 S cm-1 at 600°C. The conductivity had only a slight dependence on the partial pressure of oxygen over a wide range and was largely attributed to n-type electronic conduction. Ru-doped SrTiO3 showed mixed oxide-ionic and electronic conduction under reducing atmospheres. The mechanism of the electronic and ionic conduction is discussed.

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Electrochemical pumping of hydrogen through high temperature-type proton-conducting solid electrolytes has heen studied. The effect of water vapor introduced to the cathode on the hydrogen-pumping capacity of the SrCe0.95 Yb0.05O3-α proton conductor cell was investigated in the present study. The pumping capacity of the cell was greatly enhanced when water vapor was introduced to the cathode. The water vapor was consumed at the cathode due to the minor partial oxide ionic conduction in the electrolyte. The role of the water vapor at the cathode in the hydrogen pump is discussed. © 2001 The Electrochemical Society. All rights reserved.

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A self-referenced electrode was devised for galvanic cell-type hydrogen and steam sensors. Two proton-conducting solid electrolyte discs with porous platinum electrodes, one for electrochemical pumping of hydrogen and the other for sensing of hydrogen or water vapor, were stacked and exposed to test gases at 500-600°C; a small open pore was provided in the sensing electrolyte. When a constant current was sent to the pumping cell to draw out hydrogen at the interface of the two cells, the sensing cell indicated EMF as a function of hydrogen or water vapor activity in the test gas. This suggest that the hydrogen activity at the interface could be controlled with respect the test gas atmosphere, based on the equal rate of the hydrogen pumping and hydrogen or water vapor diffusion through the pore at the stationary state.

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Chloride ion conduction in PbCl2-PbO system, PbCl2(1-x)Ox (x = 0-0.67), was examined. Electrical conductivities were measured in air below 400°C. It was found that 3PbCl2·2PbO phase has high conductivity. From changes in current, mass and crystal phases during electrolytic polarization, chloride ion conduction was confirmed in this compound. © 2001 Elsevier Science Ltd.

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A high-temperature solid electrolyte hydrogen sensor consisting of two electrochemical cells was investigated. One cell was employed for electrochemical pumping of hydrogen from hydrogen-containing atmosphere and the other was used for sensing of the ambient hydrogen with the pumped hydrogen as a standard gas. On applying a voltage above 2.5 V to the pumping cell, a sufficient EMF response against hydrogen partial pressure was observed over a wide range of PH(2). The required voltage of the pumping cell was affected by the hydrogen partial pressure in the test gas.

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A carbon dioxide sensor using molten carbonate electrolyte with double-cell structure was examined; one cell was employed for electrochemical pumping of CO2 and O2 from ambient atmosphere and the other was used for sensing of the ambient CO2 with the pumped CO2-O2 mixture as a reference gas. The sensor was operated at 600 °C for the sensing of CO2-containing air. By sending appropriate current, the pumping cell could provide CO2 and O2 at 2/3 and 1/3 of the atmospheric pressure, respectively. The sensing cell showed EMF with respect to the CO2 and O2 partial pressures against the pumped CO2-O2 reference gas. The sensor could determine the partial pressure of CO2 in the examined range of 26 to 1×104 Pa (260-100,000 ppm).

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The current efficiency of steam electrolysis was measured in the temperature range from 460 to 600 °C using a steam electrolysis cell constructed with a partial protonic conductor SrZr0.9Yb0.1O3-α as an electrolyte and Pt cermet electrodes. The efficiency was increased with increasing partial pressure of water vapor and temperature. The results were considered in relation to the reaction rates at the anode and cathode. Under the operating conditions of steam electrolysis, the reaction rate of producing H2 from protons at the cathode was found to be faster than that of oxidizing water vapor into protons and O2 at the anode. Therefore, the average concentration of protons in the partial protonic conductor during electrolysis decreased. On the other hand, the average concentration of holes increased. This is considered to decrease the efficiency of steam electrolysis. It was found that the effective transport numbers of charge carriers in the partial protonic conductor were controlled by the reaction rates at the electrodes at relatively low temperatures at which the equilibria between the atmosphere and defects in the partial protonic conductor were difficult to obtain.

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The effect of additions (Cr, Ni and 80Ni·20Cr) on the wetting characteristics of liquid Cu on ZrO2 have been studied using a sessile drop method. Analysis of reaction layers at a solidified droplet/ZrO2 interface have been performed. Additions of 80Ni·20Cr alloy or Cr alone reduce the contact angle of liquid Cu on ZrO2. The simultaneous addition of Ni and Cr can markedly improve the wettability of liquid Cu on ZrO2. According to SEM and EPMA observations, dissolution of the additions into liquid Cu droplets occurred. A uniform distribution of Ni throughout the Cu droplet and segregation of Cr at the Cu droplet/ZrO2 interface were observed in solidified specimens.

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The EMFs of hydrogen isotope cells with H2-D2 gas mixtures against H2 and D2 reference gases were measured at 700 °C using CaZr0.90In0.10O3-α as a proton-conducting solid electrolyte. Steady electromotive forces (EMFs) with quick response were obtained. The EMFs were almost linear functions of the gas composition of the H2-D2 mixtures and were consistent with those theoretically estimated. Such defined EMFs can be used to monitor H2/D2 ratios in hydrogen isotope mixtures.

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Electrochemical dehumidification using a proton conducting ceramic as a solid electrolyte was studied. The working principle, based on the electrochemical hydrogen pump, is elucidated and experimental studies on this type of device are described. It was verified that the dehumidifier using a SrCeO3-based proton conducting ceramic worked successfully on a laboratory-scale and that the dehumidifier could desiccate the test gas to 6.7 Pa (dew point: about -45 °C). This type of device may be a convenient dehumidifier suitable for use in small, closed systems in scientific instruments.

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A high temperature solid electrolyte steam sensor with an electrochemically supplied hydrogen as a standard was designed and investigated. Two discs of proton-conducting oxide with porous platinum electrodes were stacked and a small hole was made in order to leak the gas at the interface. Constant voltage was applied to one cell in order to pump up hydrogen from water vapor in atmosphere. EMF of the other cell was measured using the pumped hydrogen as a standard gas. On applying a certain voltage, good EMF response against water vapor pressure was observed over a wide range of PH(2)O at 700°C.

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The influence of non-stoichiometry, deviation of Sr/Ce from unity, on conduction properties in SrCeO3 was investigated and compared with that in BaCeO3. In SrxCeO3-α, single phase of samples was confirmed for x = 0.98, 1.00, 1.02, 1.05 and 1.10. At x≤1.0, conduction was electronic in hydrogen and ionic in air. On the other hand, at x>1.0, the dominant conduction carriers were protons in hydrogen and electron holes in air. The dependence of conduction characteristic on x in SrxCeO3-α was similar to that in BaxCeO3-α, although there was small quantitative difference between two systems. This means that the A/Ce non-stoichiometry results in the similar type of defect structure in SrxCeO3-α and in BaxCeO3-α. In Sr- or Ba-poor region, the partial substitution of excess Ce for A-site in ABO3 perovskite may occur. At x > 1.0, the substitution of excess Sr or Ba for B-site may happen and this substitution leads to the introduction of the oxide ion vacancies in the lattice.

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Transient phenomena of electrochemical hydrogen pumps, permeation of hydrogen on passing a direct current through a proton-conducting electrolyte, were investigated. Variations of proton transport in electrochemical hydrogen permeation by changing the anode gas were investigated potentiostatically at 900 °C using a SrCe0.95Yb0.05O3-α proton-conducting solid electrolyte. Changes in direct current and charge carriers were examined on changing the anode gas from Ar to H2 and back while keeping Ar as the cathode gas. In another variation of the anode gas with the two hydrogen isotopes, H2 and D2, the time dependence of the evolution of hydrogen isotope species at the cathode was analyzed to estimate the mobilities of protons and deuterons in the electrolyte.

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Protonic conduction in oxide ceramics under hydrogen-containing atmosphere at elevated temperatures is reviewed with respect to oxide materials, their electrochemical properties, conduction mechanism and possible applications. These oxides are unique in respect of the fact that they have no protons as a host component, but incorporate protons via reactions with the atmosphere. The materials of this class are some perovskite-type oxides and other oxides which contain crystal defects. Defect equilibria for proton formation in these kinds of oxides are discussed citing some experimental results. Possible electrochemical devices using proton conducting ceramics are briefly introduced.

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Current efficiency of electrochemical hydrogen pumping from wet hydrogen gas through a SrCe0.95Yb0.05O3-α proton-conducting solid electrolyte was investigated at 900 °C. A decrease in current efficiency was observed at relatively high current density. The critical current density for the reduction of the efficiency decreased with increasing amount of water vapor in the anode hydrogen gas. Addition of a small amount of argon to the anode gas had no effect on the pumping characteristics. It was concluded that the lack of hydrogen and the increase in partial pressure of oxygen at the anode on sending high current could cause the partial hole conduction in the electrolyte and the decrease in current efficiency of the hydrogen pump.

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The electromotive force (EMF) of the hydrogen isotope cell with high-temperature proton conducting solid electrolytes was investigated. Stable and reproducible EMF was observed. The EMF could be attributed to the internal potential in the electrolyte and redox potentials of H2 and D2 gases. The former is based on the mobility differences between protons and deuterons. In addition, there would be a contribution of oxygen concentration cell to the EMF of the cell in the case of the SrCe0.95Yb0.05O3-α electrolyte due to its partial oxide ion conduction in the high-temperature region.

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Ionic conduction and Ba2+:Ce4+ site nonstoichiometry in perovskite-type oxide sinters of non-doped BaxCeO3-α (0.90 ≤ x ≤ 1.10) have been investigated. X-ray powder diffraction patterns of these sinters indicated that the specimens with 0.95 ≤ x ≤ 1.10 were a single phase of orthorhombic perovskite-type BaCeO3, while the sinter with x = 0.90 was a mixed phase of perovskite and CeO2 impurity. The conduction properties of the specimens with 0.95 ≤ x ≤ 1.05 were studied electrochemically in the temperature range of 600-1000. The conduction properties of the specimens were strongly influenced by Ba2+:Ce4+ site nonstoichiometry. The specimens with excess Ba showed a predominant ionic conduction (H+ + O2-) with ion transport number larger than 0.5 under hydrogen atmosphere, whereas they showed a poor oxide-ionic conduction (oxide-ion transport numbers < 0.1) under oxidizing atmosphere. Protonic conduction in these specimens under reducing atmosphere could be confirmed by means of electrochemical hydrogen permeation. In contrast, the specimens with x ≤ 1.00 showed a predominant oxygen-ionic conduction (oxygen-ion transport numbers > 0.8) in oxidative atmosphere, while a poor ionic conduction (ion transport numbers < 0.1) was observed in hydrogen.

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The electromotive force (EMF) of hydrogen isotope cell with a proton-conducting solid electrolyte CaZr0.90In0.10O3-α was investigated at 500 approx. 900°C. This kind of cell (H2/D2) gave steady and reproducible EMF for which the D2 side electrode was positive. The EMF could be explained by the two factors, i.e., the difference in mobilities of proton and deuteron in the electrolyte and the electrode reactions of H2 and D2 gases. The EMF of the cell for mixed isotope gases was nearly linear with the composition of hydrogen isotopes with a slight deviation and was consistent with such a mechanism of EMF of hydrogen isotope cell.

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Electrochemical regulation of hydrogen partial pressure in flowing gas was examined using a proton-conducting ceramic tube made of Yb-doped SrCeO3. Hydrogen partial pressure in the test gas was controlled by electrochemical hydrogen pump. When pumping current was controlled based on the Faraday's law, hydrogen content in the test gas with a constant flow-rate was well regulated, while change in flow-rate of the gas caused some deviation of hydrogen partial pressure from that desired. The pumping current could be determined in a self-correcting manner, which was efficient to regulate gas even with changes in flow-rate and/or initial hydrogen content in the gas. © 1999 Elsevier Science B.V. All rights reserved.

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Electrochemical properties of hexagonal lithium lanthanoid silicates were investigated to confirm their lithium ion conduction at elevated temperatures. EMF of oxygen concentration cells using the specimen as an electrolyte obeyed Nernst's equation, indicating their unique ionic conduction. The charge carrier for the ionic conduction was confirmed quantitatively to be lithium ions by means of Tubandt's method. Partial substitution of alkaline earth metals and lithium for lanthanum in LiLaSiO4 was found to be effective to enhance conductivity and to improve sintering property. © 1998 Elsevier Science B.V. All rights reserved.

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The electrodeposition mechanism of cadmium selenide, zinc selenide and zinc cadmium selenide thin films from selenosulfite has been investigated based on the results of (i) cyclic voltammetry under dark and illumination, (ii) i-t transients in the plating solution and (iii) compositional analysis of the thin films. While considerable thickness of zinc selenide film could not be deposited, almost stoichiometric cadmium selenide and zinc cadmium selenide films with different phases were deposited at different deposition potentials. The possible mechanism for lack of zinc selenide formation and different phase formation of cadmium selenide and zinc cadmium selenide at various deposition potential has been discussed.

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The electrochromic nickel hydroxide thin film was anodically deposited from an aqueous solution. The effect of solution temperature, postheat-treatment temperature, and addition of cadmium on the electrochromic behavior (color/bleach durability cycle, response time, and coloration efficiency of the nickel hydroxide films in NaOH) were investigated. A significant increase in the color/bleach durability cycle from 500 (for the as-deposited film) to more than 5000 cycles (for the heat-treated film) was observed. The addition of cadmium increased the utilization of the active materials. It was found that the coloration efficiency was 40 cm2/C and coloration and bleaching response time were 20 to 30 s and 8 to 10 s, respectively. The change in the electrochromic properties with heat-treatment temperature is discussed based on the physical and electrochemical analysis.

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The effect of additions (Cr, Ni and 80Ni·20Cr alloy) on the wetting characteristics of liquid Cu on Al2O3 has been studied using a sessile drop method in a vacuum at 1150°C. Through the use of microdesigned multilayer Cu/80Ni·20Cr/Cu interlayers, PTLP (Partial Transient Liquid-Phase) bonding of Al2O3 has been achieved in a vacuum at 1150°C. These results demonstrate that the bonding temperature, the dissolution of Cr into liquid Cu film improved the wettability of liquid Cu film on Al2O3 and facilitate the formation of reliably strong joint PTLP bonded Al2O3 using Cu/80Ni·20Cr/Cu interlayer.

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The single-phase region of La 1-xSr xCrO 3 (x=0.1, 0.2, 0.3) was precisely determined as a function of temperature, P O2 and Sr content. The powders with the nominal composition of La 1-xSr xCrO 3 were equilibrated under various conditions, and then identified by XRD analyses. To confirm the equilibration, two independent experiments were performed for each composition observing (i) the precipitation of the second phase from a single-phase solid solution, and (ii) the formation of the single phase from the constituent oxides. Two kinds of second phases, SrCrO 4 and an unknown phase, were observed depending on the conditions. The second phases tended to appear at low temperature, in high P O2 and with a large Sr content. The single-phase regions obtained via the two equilibration routes were in good agreement with each other. The thermodynamic calculations on the supposition of ideality of the solid solution essentially reproduced the experimental results. When this material is used as the interconnects of solid oxide fuel cells, much attention should be paid to its relatively narrow solubility range of Sr; for example, the solubility limit is approximately 0.1 under a typical cathode-side condition (1273K, air). © 2004 Elsevier Inc. All rights reserved.

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Responsible for pages："Hydrogen Production" Pages 147-165 "Infrastructure for Next-Generation Vehicles" Pages 217-235   Language：English   Book type：Scholarly book

Responsible for pages：Volume 255, 31 May 2016, Pages 41-46   Language：English   Book type：Scholarly book

SOFCs have the solid-state ceramic construction and operate at high-temperatures, with flexibility in fuel choice, high efficiency, stability, and reliability. The most attractive characteristics of SOFCs should be high fuel-to-electricity conversion efficiencies of as high as 50 to 60 percent LHV. For further improving the electrical efficiencies, preceding studies on multi-stage electrochemical oxidation with SOFCs have been reported. However, there are many parameters for the multi-stage oxidation, and effects of the parameters on the efficiency remains to be identified. We have investigated the multi-stage oxidation by using a symbolic analysis method. In the case of n-stage electrochemical oxidation, the fuel utilization ratio in the individual stage was found to decrease with increasing the n value at a fixed fuel utilization ratio of an entire system, resulting in the enhancement of robustness against the operation at a high fuel utilization ratio of the entire system as well as against a gas-leakage. © 2016 The American Ceramic Society. All rights reserved.

DOI： 10.1002/9781119234531.ch4

Responsible for pages：Pages 217-235   Language：English   Book type：Scholarly book

During and after the intense growth period of the economy in Japan around the 1960s, the number of fuel filling stations increased with the rapid spread of automobiles. However, two oil crises in the 1970s triggered the introduction of “next-generation vehicles.” Examples include battery electric vehicles (BEVs), compressed natural gas vehicles (CNGVs), and hydrogen fuel cell electric vehicles (FCEVs). After the 1990s, CNGVs began to be introduced, and the development of BEVs and FCEVs accelerated. However, penetration of these next-generation vehicles was not fully successful, owing to their inferior performance (range, acceleration, durability, economic efficiency, and other factors) compared with conventional internal combustion engine vehicles (ICEVs) and a lack of infrastructure, e.g., insufficient CNG stations for CNGVs. Since around 2010, the introduction of next-generation vehicles has progressed gradually. The higher price and shorter cruising range relative to ICEVs has been improved, and their infrastructure has expanded. FCEVs are scheduled to be on the market in 2015, and their hydrogen infrastructure is also being developed. This study discusses next-generation vehicles’ fuel supply infrastructure, particularly its technical goals, challenges, and risks, and surveys Japan’s past approaches and efforts and future prospects. © Springer Japan 2016.

Responsible for pages：Pages 147-165   Language：English   Book type：Scholarly book

Hydrogen production methods to meet hydrogen demand as a future fuel are considered. Current hydrogen production methods are described, and energy efficiency, CO2 emissions, and cost are discussed. After estimating possible future hydrogen use and demand, various hydrogen production methods meeting future hydrogen demand are addressed and their prospects considered. A brief conclusion is that future demand for hydrogen fuel cell electric vehicles can be met by conventional fossil fuel-based hydrogen production methods, but novel low-carbon techniques for this production using biomass, renewable energybased electrolysis, thermochemical methods, and photoelectrochemical water splitting are important to reduce CO2 emissions. The introduction of hydrogen energy provides benefits of energy saving, renewable energy use, and stabilization of energy security. © Springer Japan 2016.

Language：Japanese   Book type：General book, introductory book for general audience

Language：Japanese   Book type：General book, introductory book for general audience

Event date： 2019.6

Language：English  

Venue：PyeongChang Alpensia Resort Convention Center (Pyeong chang-Gun Gangwon-Do)   Country：Korea, Republic of  

Aliovalent cation-doped perovskite-type oxides (ABO3) exhibit proton conductivity originating from the hydration of oxide ion vacancies [1]. The hydration reaction is accompanied by structural deformation, i.e. chemical expansion. The chemical expansion may lead to mechanical failure in electrochemical devices, and thus it is necessary to understand the causes of this process at the atomic scale. In this study, the chemical expansion behaviors of Y-doped strontium cerate and zirconate were comparatively investigated. High-temperature X-ray diffraction (See Figure 1) and thermogravimetric analysis revealed that the cerate exhibits larger chemical expansion. Density functional theory calculations revealed that this tendency can be accounted for by the different atomic distribution of the Y dopant between the cerate and zirconate, which results in differences in the size of the oxide ion vacancies to be hydrated as well as different elastic character [2].

Event date： 2018.12

Language：Japanese  

Venue：京都大学吉田キャンパス   Country：Japan  

Event date： 2018.12

Language：Japanese  

Venue：京都大学吉田キャンパス   Country：Japan  

Event date： 2018.9

Language：English   Presentation type：Oral presentation (general)  

Venue：The University of Tennessee, Knoxville   Country：United States  

Steam electrolysis is characterized by high energy conversion efficiency compared to low temperature PEM and alkaline water electrolysis, and thus is useful for hydrogen production particularly from renewable energy. Proton conducting perovskites are studied to apply to steam electrolysis for intermediate-temperature operation. We have reported so far SrZr0.5Ce0.4Y0.1O3-δ (SZCY541) and BaZr0.44Ce0.36Y0.2O3-δ (BZCY(54)8/92) to be suitable as the proton-conducting electrolytes for steam electrolysis, having both sufficient conductivity, e.g. 1.44 × 10-2 S cm-1 in wet 1 % H2 at 600°C in BZCY(54)8/92, and acceptable stability in steam at operation temperatures. In this paper, our state-of-the art steam electrolysis performance using these electrolyte materials is reported and challenges existing for their practical use is discussed.
Fig. 1 shows the i-V characteristics and H2 evolution rates of a steam electrolysis experiment conducted with BZCY(54)8/92 with different thickness at 600°C. A cell terminal voltage of 1.45 V at a current density of 500 mA cm-2 with Faradaic efficiency of ~ 0.82 was obtained (T: 12 µm). From these quantities, the electric power necessary for producing 1 Nm3of H2 is calculated to be 4.2 kWh.
Electronic leakage seen in Fig. 1 (b), Ohmic resistance higher than that estimated from the original conductivity, and so on are the challenges and are discussed with experimental data.

Other Link： https://sspc19.utk.edu/

Event date： 2018.9

Language：English  

Venue：The University of Tennessee, Knoxville   Country：United States  

Ion conduction in ceramic materials needs high temperature due to the necessity of thermal activation for the ionic defects to move through the crystal lattice. Analogous to the proton conduction in polyelectrolyte, the surface of hydrated metal oxide grains possibly works as proton conduction pathway with the aid of adsorbed water as conceptually shown in Fig. 1. We have reported so far high protonic conduction in Anatase nanoparticles surface-modified with sulphuric acid [1], but the sulphuric acid gradually detached on soaking with water, suggested by decreasing pH of the surrounding water. Recently, Wu et al., reported the synthesis of hydrated titania, H2Ti2O5・H2O, via a solvothermal method [2]. This work has utilized this material to investigate possible proton conduction on the surface of hydrated metal nan oxide.
H2Ti2O5・H2O was prepared in the method reported in the literature [2], and spherical nano particles are obtained. XRD measurement revealed the layered structure which phase was stable up to 290°C; further increase in the temperature resulted in dehydration to deform to Anatase. The obtained powder compacted in a rectangular bar shape showed high resistance in air but the resistance markedly decreased when soaked in water: a conductivity of 7.55×10-3 s・cm-1 was obtained in water at 90°C. pH was maintained almost neutral and the conductivity seems to take place not through water. We tried to use this material for water electrolysis and evolution of hydrogen and oxygen was confirmed [3]. From these results, it is conclusive that this material has a significant ionic conduction in water or at high liquid water activity.

Other Link： https://sspc19.utk.edu/

Event date： 2018.9

Language：English  

Venue：The University of Tennessee, Knoxville   Country：United States  

Hydration of oxide ion vacancy is a part of the mechanism of proton conduction to take place in aliovalent-cation-doped metal oxides but leads to chemical expansion at the critical temperature, typically 400-600°C, where the degree of hydration changes. Thus, high proton concentration that may lead to high proton conductivity will be accompanied by large chemical expansion that causes mechanical failure of the ceramic specimens. In the case of AB1-xMxO3-δ perovskite-type proton-conductors, the level of dopant M is mostly limited to 20% to the total molar amount of M and B, because highly doped specimens frequently break during preparation or conductivity measurement. In this study, we have investigated the relation between the dopant level and chemical expansion, and then a dry atmosphere or vacuum is partly introduced for the sintering and the heating-cooling during the conductivity measurement.

Other Link： https://sspc19.utk.edu/

Event date： 2018.9

Language：English  

Venue：The University of Tennessee, Knoxville   Country：United States  

Steam electrolysis using proton conducting electrolytes (PC-SOECs) are potentially the most efficient and cost-effective option for hydrogen production at intermediate temperatures (400–600 °C) from renewable sources. These class of electrolytes are particularly favored for their relatively high ionic conductivities within this regime. Although significant progress has been made with small scale laboratory type PC-SOECs devices, a significant challenge has been upscaling robust and affordable planar type devices for comercialisation. The fabrication of such multilayered devices via a tape casting process requires careful control of shrinkages of individual layers to prevent warping, cracking or even delaminating during sintering.

Other Link： https://sspc19.utk.edu/

Event date： 2018.9

Language：Japanese  

Venue：湯沢ニューオータニ（新潟県南魚沼郡湯沢町湯沢）   Country：Japan  

Event date： 2018.9

Language：Japanese  

Venue：湯沢ニューオータニ（新潟県南魚沼郡湯沢町湯沢）   Country：Japan  

Event date： 2018.9

Language：Japanese  

Venue：湯沢ニューオータニ（新潟県南魚沼郡湯沢町湯沢）   Country：Japan  

ペロブスカイト構造を有するプロトン伝導性酸化物は、400℃から600℃のプロトン伝導の優位性により、燃料電池や水蒸気電解装置への応用が期待されている。プロトン伝導性酸化物は酸素空孔を有し、湿潤環境の下、約600℃以下から酸素空孔に対して水和が起こり始める。その水和はプロトン伝導の要因となっている一方、水和により化学膨張を引き起こすことが知られている。化学膨張は燃料電池や水蒸気電解装置の構成部品を破損させる原因となり得るため、化学膨張の度合いは小さい方が望ましい。本研究は、ペロブスカイト構造のAサイトにSrを用いた際、 B-サイトのCeとZrが化学膨張に与える影響について、第一原理計算により比較を行った。また計算結果は高温X線回折法によっても比較された。

Event date： 2018.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Sheraton Vancouver Wall Centre Hotel | Vancouver, BC Canada   Country：Canada  

Low temperature operation of solid oxide electrochemical devices such as fuel cell and electrolyzers can reduce both manufacturing and materials cost of such systems [1-3]. One approach can be the use of proton-conducting electrolytes since their activation energy for proton conduction (0.3-0.6 eV), is lower compared to oxygen-ion conducting electrolytes. In addition, such proton conducting electrolytes are very promising for steam electrolyzers to generate hydrogen, utilizing renewable energy sources [1, 3]. The vast majority of research in this area has focused on the electrolytes, with a range of materials being shown to exhibit high proton conductivity [2]. However, a key factor limiting progress in this area is the sluggish catalytic activity of the air/oxygen electrodes. For this purpose, some double perovskite oxide like BaGd0.8La0.2Co2O6−δ (BGLC) [1] has been reported to exhibit, electronic (p-type), oxygen ion and protonic conduction.
In this paper, we investigate and compare the performance and cell polarization resistances of Ba0.5La0.5CoO3 (BLC) and double perovskite oxide BGLC anode on cathode supported protonic electrolysis cells using a 20μm SrZr0.5Ce0.4Y0.1O3-δ (SZCY541) electrolyte with Ni-SZCY541 composite as the H2-electrode. Also Isotope exchange experiments (18O and 2H2O tracers), Tritium imaging and Time-of-Flight Secondary Ion Mass Spectrometry depth profiling were used to study the proton uptake in the dense ceramic pellets of both materials as a means of broadening current knowledge on the availability of protons and to clarify the relationship between protons and oxide ions conduction. The BGLC 2H distribution, as inferred from the 2H216O− signal, shows an apparent depth profile which could be interpreted as 2H diffusion. Our data also suggest BGLC can indeed incorporate protons in the bulk relative to BLC at 300 ºC and that both materials retains appreciable mixed oxygen ion/electron conduction behavior. Tritium imaging plate technique however showed similar levels of protons in both materials (~5х10-8mol H/g), which are about one order of magnitude lower than that of BaZr0.44Ce0.36Y0.2O2.9 (~2,9х10-7mol H/g) at 600ºC These results will be presented together with recent work on protonic electrolysis cells.

Other Link： http://ceramics.org/mcare2018

Event date： 2018.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Sheraton Vancouver Wall Centre Hotel | Vancouver, BC Canada   Country：Canada  

Electrochemical devices such as solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) are promising environmentally friendly alternative technologies for sustainable energy production. These devices generally consist of two porous electrodes separated by a dense electrolyte membrane and classified by the type of electrolyte used. Traditionally, oxide ion conducting zirconia and ceria based electrolytes have been favored for such devices, although very recently proton conducting alkaline earth cerates, zirconates and their solid solutions based electrolytes have also been attracting growing interest for lower temperature operation (600 ~ 400 °C). We have recently made significant progresses in the development of our steam electrolysis devices in two fronts. Starting from SrZr0.5Ce0.4Y0.1O3-we examined the effects of Ba substitution for Sr and the doping level of Y on the lattice structure, electrical properties, as well as chemical stability. BaZr0.44Ce0.36Y0.2O3-δ our state-of–the-art electrolyte retained a conductivity of 1.44 × 10-2 Scm-1 in wet 1 % H2 at 600°C. A cell terminal voltage of 1.45V at a current density of 500mAcm-2 with ~82 % hydrogen production efficiency was also obtained under electrolysis mode.
In this presentation we will discuss some of the challenges of these proton conductors particularly for electrolysis mode of operation. On the anode side, Several transition metal containing perovskites, such as Sm0.5Sr0.5CoO3 (SSC55) can be used with acceptable electrode performance, but these materials are not sufficiently durable against high steam concentration at intermediate temperature. Another issue is the inter-diffusion of transition metal species from the electrodes to the electrolyte causing the reduction of the proton conductivity. We have examined the impact of several transition metals by introducing them as a part of the B-site component of AB0.9Y0.1O3-δ (A=Ba, Sr; B=Ce, Zr) and found that proton conductivity is more or less reduced by the transition metal incorporation. In addition, preliminary results of our recent efforts in fabricating and scaling up our protonic membrane devices by sequential tape casting will be presented.
Acknowledgement
This work was supported by the Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), "energy carrier" (Funding agency: JST) and by World Premium International Research Center Initiative (WPI), MEXT Japan.

Other Link： http://ceramics.org/mcare2018

Event date： 2018.6

Language：English  

Venue：Dresden   Country：Germany  

Electrochemical devices such as solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) are promising environmentally friendly alternative technologies for sustainable energy production. These devices generally consist of two porous electrodes separated by a dense electrolyte membrane and classified by the type of electrolyte used. Traditionally, oxide ion conducting zirconia and ceria based electrolytes have been favored for such devices, although very recently proton conducting alkaline earth cerates, zirconates and their solid solutions based electrolytes have also been attracting growing interest for lower temperature operation (600 ~ 400 °C). We have recently made significant progresses in the development of our steam electrolysis devices in two fronts. Starting from SrZr0.5Ce0.4Y0.1O3-we examined the effects of Ba substitution for Sr and the doping level of Y on the lattice structure, electrical properties, as well as chemical stability. BaZr0.44Ce0.36Y0.2O3-δ our state-of–the-art electrolyte retained a conductivity of 1.44 × 10-2 Scm-1 in wet 1 % H2 at 600°C. A cell terminal voltage of 1.45V at a current density of 500mAcm-2 with ~82 % hydrogen production efficiency was also obtained under electrolysis mode.
In this presentation we will discuss some of the challenges of these proton conductors particularly for electrolysis mode of operation. On the anode side, Several transition metal containing perovskites, such as Sm0.5Sr0.5CoO3 (SSC55) can be used with acceptable electrode performance, but these materials are not sufficiently durable against high steam concentration at intermediate temperature. Another issue is the inter-diffusion of transition metal species from the electrodes to the electrolyte causing the reduction of the proton conductivity. We have examined the impact of several transition metals by introducing them as a part of the B-site component of AB0.9Y0.1O3-δ (A=Ba, Sr; B=Ce, Zr) and found that proton conductivity is more or less reduced by the transition metal incorporation. In addition, preliminary results of our recent efforts in fabricating and scaling up our protonic membrane devices by sequential tape casting will be presented.

Event date： 2018.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Washington State Convention Center　705 Pike St, Seattle, WA   Country：United States  

The interface of two materials having different work function leads to the development of space charge, resulting in the change of defect equivalence and hence the change in the charge carrier concentration. Another possibility lies in the formation of strain at the interface resulting in the change of the mobility of ionic charge carriers. If we can use these effects for the enhancement of ionic conductivity, introduction of hetero-interface is a potential guideline for designing new ion conduction in solids.
We have reported previously that when Pt nanoparticles precipitate in proton conducting SrZr0.9Y0.1O3-δ (SZY), the electrical conductivity decreases markedly due to nanoionics effects; small amount of Pt can be dissolved into the Zr site and becomes zero-valent upon exposure to hydrogen [1]. Such a change in the macroscopic electrochemical properties is considered as a result of the unique microscopic electrochemical properties of the nanoscale space charge layer generated in the vicinity of the interface when the Pt nanoparticles are precipitated [2]. Using electrochemical spectroscopy, SrCe0.95Yb0.05O3-δ (SCYb) and Sr(Zr,Ce,Y)O3 proton conducting oxide thus doped with Pt were investigated with the aim to clarify the effects and mechanism of the Pt/oxide interface on the electrical properties of proton conducting oxide.
Pt-doped proton conducting oxides were prepared by combustion synthesis method. The electrical conductivity of Pt-SZY and Pt-SCYb measured at 800 °C under 1% H2 and air atmospheres revealed a reversible nanoionics phenomenon as a result of precipitation and dissolution of platinum nanoparticles (Fig.1). The electrical conductivity then decreases significantly when the atmosphere is change to hydrogen for Pt-SZY. In the case of Pt-SCYb an increase in the conductivity can be seen for the same changes of the atmosphere. This change in electrical conductivity has been explained by the effect of precipitated Pt particles. In other words, a proton deficient region is formed in the vicinity of the interface between Pt and SZY whereas at the interface between Pt and SCYb, there is no such influence.
Also, this result can be applied to deepen understanding of the reaction at the electrodes of the electrochemical cell. Comparing the electrode overvoltage when SZY and SCYb are used for the electrolyte in a cell using Pt as the electrode, SZY is several orders of magnitude larger than SCYb [3]. The reason for this can be explained if it is thought that the region where protons are not present is formed near the interface of Pt / SZY like as the case of Pt nanoparticles disperse in the bulk of SZY. On the other hand, the reason why the overvoltage at Pt/SCYb interface is smaller than that at SZY is considered to be a reasonable result of the loss of protons not taking place significantly near the interface.

Event date： 2018.3

Language：Japanese  

Venue：東京理科大学　葛飾キャンパス（葛飾区新宿6-3-1）   Country：Japan  

プロトン伝導性酸化物は、酸化物イオン伝導体と比べ低い温度領域においてより高い電気伝導性を持つため、固体酸化物燃料電池（SOFC）や水蒸気電解（SOEC）の低温作動化に役立つと期待される。そこで当研究室では、より高い電気伝導性、化学的安定性を持つ電解質の開発を目指し、BaZrxCeyY1-x-yO3-δ（以下BZCY系と記す）に注目した。これまでにBaZr0.44Ce0.36Y0.2O3-δにおいて高いプロトン伝導性が発現することを報告しているが[1]、BZCY系の他の組成では試料の作製過程で割れが発生するものがあった（BZCY-aおよび-bと称す）。プロトン伝導性は酸素空孔の水和によって発現する。一方、水和時に格子体積の膨張が起こることが知られている[2]。この体積変化が大きいために割れが発生している場合、材料の水和量が大きい、つまり高いプロトン伝導性を持つ材料であることが期待される。そこで本研究では、水和による膨張と関連付けながら、割れの発生のメカニズムを考察し、割れ発生を回避する新規焼成プロセスおよび作製された試料の電気化学的特性について検討した。

Other Link： https://confit.atlas.jp/guide/event/ecsj2018s/top

Event date： 2018.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京理科大学　葛飾キャンパス（葛飾区新宿6-3-1）   Country：Japan  

本研究室では、無機多孔質材料を電解質とした吸水多孔質電解質水電解セルの開発を進めている。本セルは、プロトン伝導性の無機多孔電解質層を撥水触媒層と撥水性ガス拡散層で挟み込む構造である（Fig.1 (a)）。そのため、多孔質電解質層を通じて電極層への水供給が容易であり水枯れが起こりにくい。また、加圧供給した水を撥水触媒層で塞き止めるため、高圧下で水電解を行うことが可能である。これまでの研究では、高電気伝導性を示す硫酸修飾チタニアを使用してきたが、水電解使用環境下で硫酸基が脱離する問題（酸溶出）が発生した。1本セルの作動するためには酸溶出の少ない高伝導性の材料が必要であり、固体酸の一種である層状チタンナノ粒子に着目することにした。本発表では、層状チタニアナノ粒子を電解質層に用いたセルの作製方法と、その電解特性について説明する。

Other Link： https://confit.atlas.jp/guide/event/ecsj2018s/top

Event date： 2018.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京理科大学　葛飾キャンパス（葛飾区新宿6-3-1）   Country：Japan  

我々は新規水電解の手法として、吸水多孔質電解質水電解セルについて検討している。図1に模式的に示すように、無機ナノ粒子界面をプロトン（H+）伝導場とする界面プロトン伝導体を電解質として用いることを特徴としており、アルカリ水電解や高分子形水電解に比べて、高い温度で作動できる可能性を持つ。プロトン伝導性のナノ粒子として、表面にプロトンを持つ固体酸が利用できる可能性がある。Wuらはソルボサーマル法によりチタンアルコキシドからプロトン化された酸化チタン化合物、H2Ti2O5・H2Oが合成できることを報告している1。この材料は層状のチタニアであり、チタンナノシートの間にプロトンが入っている構造であるとされている。本研究では、この材料のイオン伝導性を調べた。DLS、XRD、TG、IR、TEMによるキャラクタリゼーションの結果及び、水中イオン伝導性について報告する。

Other Link： https://confit.atlas.jp/guide/event/ecsj2018s/top

Event date： 2018.3

Language：Japanese  

Venue：東京理科大学　葛飾キャンパス（葛飾区新宿6-3-1）   Country：Japan  

水電解は、再生可能エネルギーを利用した水素製造の観点から重要である。本研究室では、100℃以上の高温、5気圧以上での高圧条件を目指し、無機多孔質材料を電解質層として用いた水電解セルの開発を進めている1。本研究では、前記の水電解セルに適用可能な耐水性、ガス透過性、電子伝導性全てを有する、撥水電極触媒層を作製した。本発表では種々の材料組成により作製したガス拡散層(GDL層)と電極触媒層の評価結果とそれを用いた水電解特性について説明する。

Other Link： https://confit.atlas.jp/guide/event/ecsj2018s/top

Event date： 2018.3

Language：English   Presentation type：Oral presentation (general)  

Venue：東京理科大学　葛飾キャンパス（葛飾区新宿6-3-1）   Country：Japan  

Lowering the operation temperature of solid oxide electrolysis cells (SOECs) is an attractive concept, which avoids many of the inconveniences related to high temperature operation. Proton-conducting electrolytes (PCEs) offer some unique advantages for SOECs; one because of their low activation energy for proton motion between 400 and 600 ºC. However, there are no reported air electrode materials tailored for use with PCEs application. In the present work, Isotope exchange experiments (18O and 2D2O tracers) and Time-of-Flight Secondary Ion Mass Spectrometry depth profiling were used to study proton uptake in dense ceramic pellets of Ba0.5La0.5CoO3−δ (BGLC) and BaGd0.8La0.2Co2O6−δ (BGLC). The BGLC 2D distribution, as inferred from the 2D216O− signal, shows an apparent depth profile, which could be interpreted as 2D diffusion. Our results suggest BGLC incorporate protons in the bulk relative. We subsequently exemplify performance of both materials in in a typical steam electrolysis cell at 600°C, using SZCY541 electrolyte with Ni-SZCY541 composite as cathode.

Other Link： https://confit.atlas.jp/guide/event/ecsj2018s/top

Event date： 2018.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京理科大学　葛飾キャンパス（葛飾区新宿6-3-1）   Country：Japan  

ペロブスカイト構造(ABO3)を有するプロトン伝導性酸化物は、400℃から700℃での温度領域で優れたプロトン伝導性を有していることから、燃料電池や水蒸気電解装置への応用が期待されている。湿潤環境下で700℃から温度を下げていくと、プロトン伝導性酸化物は約600℃以下の温度領域で水和による化学膨張が起こることが知られている1。化学膨張は燃料電池や水蒸気電解装置の構成部品を破損させる原因となり得るため、化学膨張が小さいことが望ましい。本研究では、プロトン伝導性酸化物のBサイトにセリウムとジルコニウムを選択したときの化学膨張に対する影響を、第一原理計算により検討した。また、実際に調製した試料について高温X線回折測定により格子体積の温度依存性を求め、計算の結果と比較した。

Other Link： https://confit.atlas.jp/guide/event/ecsj2018s/top

Event date： 2017.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：山形　天童温泉　ほほえみの宿　滝の湯   Country：Japan  

Proton availability in the bulk of Ba0.5La0.5CoO3−δ (BGLC) and BaGd0.8La0.2Co2O6−δ (BGLC) has been investigated using TOF-SIMS depth profiling. The cell performance of both materials was also evaluated on cathode supported protonic electrolysis cells at 600 ºC. TOF-SIMS results show that, BGLC can incorporate protons into the bulk relative to BLC.

Event date： 2017.12

Language：English   Presentation type：Oral presentation (general)  

Venue：山形　天童温泉　ほほえみの宿　滝の湯   Country：Japan  

Proton availability in the bulk of Ba0.5La0.5CoO3−δ (BGLC) and BaGd0.8La0.2Co2O6−δ (BGLC) has been investigated using TOF-SIMS depth profiling. The cell performance of both materials was also evaluated on cathode supported protonic electrolysis cells at 600 ºC. TOF-SIMS results show that, BGLC can incorporate protons into the bulk relative to BLC.

Event date： 2017.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Bordeaux   Country：France  

Proton conductor has been regarded as electrolyte materials for solid oxide fuel cells (SOFC) and electrolysers (SOEC). Given that proton conductor could reduce operating temperature for SOFC/SOEC system, this system will extend wildly applications. Oxides containing transition metals are commonly utilized as electrodes. During preparation and operation process, transition metals would diffuse from anode or cathode to the electrolyte. These phenomena caused to degrade the electrolyte conductivity. Shimura et al. shows significant decrease in the conductivity of BaCe0.9Y0.1O3-δ-based proton conductors when partial replacement of Fe, Mn and Co for Ce [1]. In addition, Leonard et al. reported that Ba(Zr0.5Ce0.4)0.8Y0.2O3-δ (BZCY542) has a high proton mobility and chemical stability [2]. The BCZY542 could be considered as a suitable electrolyte material for SOFC/SOEC. In this study, therefore, the transition metal doping BZCY542-based materials were fabricated, i.e., Ba(Zr0.5Ce0.4)0.75Y0.2M0.05O3-δ (M = Co, Fe and Ni), and the effect of transition metals were investigated on their electrical conduction properties.
BZCY542-based materials were prepared by a chemical solution method. Phase identification was carried out by X-ray diffraction. The conductivity was measured by a four-terminal AC impedance method.
Figure 1 shows that the introduction of transition metals resulted in the reduction conductivity of the BZCY-based materials under air and H2 atmosphere. Furthermore, the conductivity tendency of BZCYNi, comparing with BZCYCo and BZCYFe, changed more significantly in 1% H2 atmosphere than in air atmosphere. It is suggested that the difference between in air and in H2 condition may result from the tendency to absorb O-H and the change of proton transport number.

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ホルトホール大分，ホテルソラージュ大分・日出   Country：Japan  

SrCe0.95Yb0.05O3-αやBaCe0.8Y0.2O3-αなどを典型的な組成とする「プロトン伝導性希土類複合酸化物」は、高温でプロトン（水素イオン）による電気伝導性を発現する固体酸化物であり、1980年頃にSrCeO3系のペロブスカイト型酸化物が有意なプロトン伝導性を持つことが、岩原らにより報告された。おもにAサイトが2価、Bサイトが4価の金属カチオンからなるABO3型のペロブスカイト型構造を基本とし、Bサイト元素として典型的にZrとともにCeが用いられ、その一部を3価のYやYbなどで置換することが、その材料設計である。このような操作により生じた酸素空孔にガス雰囲気中の水蒸気が取り込まれることにより、プロトン（水素イオン）が格子間イオンとして取り込まれ、これがイオン伝導種として働く。
一方、筆者は近年、金属酸化物の界面に生じる酸点着目し、これを利用した低温におけるプロトン伝導性に関する検討を行っている。固体酸・塩基性は従来、不均一触媒において議論され、利用されてきたが、酸点に存在するH+が可動であるかについてはこれまであまり検討されていない。しかし、固体高分子型燃料電池の電解質として用いられるパーフルオロスルホン酸（ナフィオンなど）は、高分子を基材として界面に酸点を持つ材料であり、良好なプロトン伝導性を示す。これと同様に無機酸化物表面の酸点がプロトン伝導性を生じてもおかしくはない（いわゆる、無機ナフィオン）
本発表では、いずれもセラミックス材料である上記のバルク型および表面型のプロトン伝導性に関してこれまでにわかってきたこと、そして、まだあまりわかっていないことがそれぞれどのようなことであるか述べたい。
電気化学デバイス、すなわち電極と電解質からなる電気化学セルを用いたデバイスは、そのエネルギー変換、物質分離・変換、検知などの機能が様々に応用されている。特に、二酸化炭素排出の抑制が急務である現在、電気化学的エネルギー変換の効率の高さは、省エネルギーや蓄エネルギー技術として役立っている。二次電池は、電子機器およびEV用の変換効率の高い（したがって、熱散逸が少ない）蓄電に利用されている。家庭用燃料電池（エネファーム）の中には、火力発電の平均を上回る効率で、各家庭で発電できるものもある。筆者は特に、上記の材料による水素製造に着目し、水／水蒸気電解の検討を行っている。異なる二種類の材料を用いた電解にはそれぞれ、特徴や長所、短所が存在する。検討例と合わせてこれを紹介したい。

Event date： 2017.9

Language：Japanese  

Venue：ホルトホール大分，ホテルソラージュ大分・日出（大分県大分市金池南1丁目5-1、大分県速見郡日出町大神7505）   Country：Japan  

当研究室では、これまでにプロトン伝導性酸化物であるSrZr0.9Y0.1O3-δ中にナノサイズのPt粒子を析出させると、界面での電子の授受により酸化物側が負に帯電することでプロトンの伝導を阻害し、電気伝導度が著しく低下することを報告している(ナノイオニクス現象)。一方で、SrCe0.95Yb0.05O3-δではPt粒子を析出させ、ヘテロ界面を導入しても電気伝導度の低下は確認されないが、この原因については、いまだ明らかになっていない。本研究ではPtの析出に伴い生じるヘテロ界面が、欠陥平衡式やイオン伝導機構に及ぼす影響を明らかにすることを目的とした。

Event date： 2017.9

Language：Japanese  

Venue：ホルトホール大分，ホテルソラージュ大分・日出（大分県大分市金池南1丁目5-1、大分県速見郡日出町大神7505）   Country：Japan  

プロトン伝導性酸化物は、酸化物イオン伝導体と比べ低い温度で高い電気伝導性を持つため、水蒸気電解システムの耐久性の向上や低コスト化に役立つと期待されている。しかし、酸化物イオン伝導体と比べ、プロトン伝導性酸化物は、水蒸気やCO2に対し化学的安定性が低く、かつ作動時の電気伝導性が低いという欠点がある。そこで当研究室では、より高い電気伝導性、化学的安定性を持つ電解質の開発を目指し、BaZrxCeyY1-x-yO3-δ（BZCY）に注目した。一方、セルの作製段階でBZCY試料に割れが発生するものが確認された。プロトン伝導性酸化物は酸素空孔の水和によってプロトン伝導性を発現し、また、水和時に格子体積の膨張が起こることが知られている。本研究では、水和による膨張と関連付けながら割れ発生のメカニズムを解明し、新規焼成プロセスの確立を目指した。

Event date： 2017.9

Language：English  

Venue：ホルトホール大分，ホテルソラージュ大分・日出（大分県大分市金池南1丁目5-1、大分県速見郡日出町大神7505）   Country：Japan  

ペロブスカイト構造を有するプロトン伝導性酸化物(一般式：AB1-xMxO3-δ)は、水蒸気雰囲気において400℃から800℃程度の温度でプロトン伝導性を発現する。近年、Ptを固溶させたプロトン伝導体の一種であるSrZr0.9Y0.1O3-δは、水素中でPtナノ粒子が析出し電気伝導率が下がることが報告された。一方、Ptを固溶させたSrCe0.95Yb0.05O3-δは、水素中で同様にPtナノ粒子が析出し、電気伝導率が上がることが報告された[1]。本研究は、上記の二つの現象が析出したPtナノ粒子とプロトン伝導性酸化物のヘテロ界面において、電荷の移動が起こり互いの欠陥平衡に影響を及ぼした可能性を挙げ、第一原理計算により調査を行った。

Event date： 2017.9

Language：English  

Venue：コテージヒムカ・宮崎フェニックスシーガイアリゾート（宮崎市山崎町浜山）   Country：Japan  

ペロブスカイト構造を有するプロトン伝導性酸化物(一般式：AB1-xMxO3-δ)は、水蒸気雰囲気において400℃から800℃程度の温度でプロトン伝導性を発現する。近年、Ptを固溶させたプロトン伝導体の一種であるSrZr0.9Y0.1O3-δは、水素中でPtナノ粒子が析出し電気伝導率が下がることが報告された。一方、Ptを固溶させたSrCe0.95Yb0.05O3-δは、水素中で同様にPtナノ粒子が析出し、電気伝導率が上がることが報告された[1]。本研究は、上記の二つの現象が析出したPtナノ粒子とプロトン伝導性酸化物のヘテロ界面において、電荷の移動が起こり互いの欠陥平衡に影響を及ぼした可能性を挙げ、第一原理計算により調査を行った。

Event date： 2017.9

Language：Japanese  

Venue：コテージヒムカ・宮崎フェニックスシーガイアリゾート（宮崎市山崎町浜山）   Country：Japan  

当研究室では、これまでにプロトン伝導性酸化物であるSrZr0.9Y0.1O3-δ中にナノサイズのPt粒子を析出させると、界面での電子の授受により酸化物側が負に帯電することでプロトンの伝導を阻害し、電気伝導度が著しく低下することを報告している(ナノイオニクス現象)。一方で、SrCe0.95Yb0.05O3-δではPt粒子を析出させ、ヘテロ界面を導入しても電気伝導度の低下は確認されておらず、Ptの析出に対する応答が異なる原因については、いまだ明らかになっていない。
本研究ではSrCe0.95Yb0.05O3-δ、YbをYに置換したSrCe0.95Y0.05O3-δ、SrZr0.9Y0.1O3-δのZrを一部Ceに置換したSrZr0.9-xCexY0.1O3-δ (0≦x≦0.9)に、析出時に0.5vol%となるようにPtを加えた試料を用いた。構成元素の異なる試料を比較することで、Ptの析出に伴い生じるヘテロ界面が、欠陥平衡式やイオン伝導機構に及ぼす影響を明らかにすることを目的とした。

Event date： 2017.9

Language：English  

Venue：コテージヒムカ・宮崎フェニックスシーガイアリゾート（宮崎市山崎町浜山）   Country：Japan  

Proton conducting electrolytes (PC) are promising intermediate temperature alternative to oxide ion conducting electrolytes (OC) in electrolysis and solid oxide fuel cells. Interest in PC stems from their high conductivity and low migration energy barriers which are usually within the range [1, 3]. A major concern with intermediate temperature operation is the sluggish kinetics, as well as high polarization resistance of the steam electrode materials particularly at high current densities. Mixed proton/electron conductor (P-MIECs) materials with protonic conductivity exceeding 10-5-10-4 to initiate a bulk transport path can significantly alleviate such drawbacks, since the reactive zone within such materials can be extended well beyond the gas/electrode/electrolyte triple phase boundary [1].
In this work, cathode supported protonic electrolysis cells using a 25μm SrZr0.5Ce0.4Y0.1O3-δ electrolyte with Ni-SZCY541 composite as the H2-electrode and double perovskite oxide BaGd0.8La0.2Co2O6−δ (BGLC) as the anode was investigated. The oxygen and proton transport properties through the bulk and across the gas electrolyte interfaces of BGLC was also studied by direct measurement of the tracer diffusions and surface exchange coefficients using a combination of stable isotope exchange experiments (18O and 2D2O tracers) and Time-of-Flight Secondary Ion Mass Spectrometry depth profiling.

Event date： 2017.8 - 2017.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Yoshida Campus, Kyoto University, Kyoto   Country：Japan  

Event date： 2017.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Yinchuan,Ningxia   Country：China  

Water electrolysis is an important technology for producing renewable hydrogen and work for energy conversion between the electricity and hydrogen in combination with hydrogen fuel cells. Steam electrolysis is characterized by low electrolysis voltage in comparison with other methods, but the drawback is high operation temperature. Proton conduction in metal oxides is less temperature-dependent than oxide ion conduction in zirconia, and this aspect enables us to operate steam electrolysis at intermediate temperatures.
This paper demonstrates conductivity and stability of some perovskite-type proton conducting metal oxides and the intermediate temperature operation of steam electrolysis. We also discuss several challenges of the proton conductor cells particularly for the electrolysis mode of operation.

Other Link： http://www.c-mrs.org.cn/cmc2017/en/index.asp

Event date： 2017.7

Language：Japanese  

Venue：北九州国際会議場   Country：Japan  

Event date： 2017.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Padua   Country：Italy  

Ceramic proton conducting electrolytes are promising intermediate temperature alternative to oxide ion conducting electrolytes in steam electrolysis cells (SOECs) and solid oxide fuel cells (SOFCs). This stems from their lower activation energy for H+ motion and ability to produce fairly pure H2 at the cathode side wheras tradition oxide ion conducting electrolytes leave wet H2 at the steam side when operated in electrolysis mode. A major concern with intemediate temperation operation is the sluggish kinetics, as well as high polarization resistance of the steam electrode materials particularly at high current densities and low faradaic efficiencies. Mixed proton/electron conductor (P-MIECs) materials with protonic conductivity exceeding 10-5-10-4 to initiat a bulk transport path can significantly alliviate such drawbacks, since the reactive zone within such materials can be extended well beyond the gas/electrode/electrolyte triple phase boundary. Very recently Ba0.5Sr0.5Fe0.8Zn0.2O3-δ (BSFZ) [1] and double perovskite oxide BaGd0.8La0.2Co2O6−δ (BGLC) [2] were proposed as possible mixed proton/electron conductors (P-MIECs) on acount of their considerable protonation between 300–400 °C. Although these materials works effectively on proton conducting electrolytes very few studies have probe the specific ionic carriers responsible for transport within the bulk of such materials.
In the present contribution, cathode-supported protonic electrolysis cells using a 25μm SrZr0.5Ce0.4Y0.1O3-δ electrolyte [3] with Ni-SZCY composite as the H2-electrode and BGLC as the anode was investigated. The assembled cells was tested with humidified 1%O2 (∼80% H2O) fed in at the steam electrode and 1%H2-99% Ar at the H2-electrode. The area specific resistance associated with the steam electrode polarization process between 500~700 °C was also measured by AC impedance spectroscopy whereas the voltage drop across the cells was measured by current interrupt method. The oxygen and proton transport properties through the bulk and across the gas electrolyte interfaces of BGLC was also studied by direct measurement of the tracer diffusions and surface exchange coefficients using a combination of stable isotope exchange experiments (18O and 2D2O tracers) and Time-of-Flight Secondary Ion Mass Spectrometry depth profiling (ToF-SIMS). This paper discusses these aspects as well as the interaction between P-MIECs electrode kinetics, total cell voltage, hydrogen generation efficiency and their implication on protonic steam electrolysis cells.

Event date： 2017.6

Language：English  

Venue：Padua   Country：Italy  

We have reported previously that when nano-sized Pt particles precipitate in proton conducting SrZr0.9Y0.1O3-δ (SZY), the electrical conductivity decreases markedly due to nanoionics effects [1]. Such a change in the macroscopic electrochemical properties is considered as a result of the unique microscopic electrochemical properties of the nanoscale space charge layer generated in the vicinity of the interface when the Pt nanoparticles are precipitated [2]. Using electrochemical spectroscopy, Pt doped SrCe0.95Yb0.05O3-δ (SCYb) and Sr(Zr,Ce,Y)O3 proton conducting oxide were investigated with the aim to clarify the effects and mechanism of the Pt / oxide interface on the electrical properties of protonic conducting oxide. Furthermore, the voltage drop at the electrode / electrolyte interface in electrochemical cells comprising Pt/ Sr(Zr,Ce,Y)O3/Pt were also measured using current interruption method in order to adequately compare and contrast these effects on proton conducting oxide. Based on the obtained knowledge, we aim to construct a novel electrode / electrolyte having excellent functionality. Pt-doped proton conductivity oxides were prepared by combustion synthesis method. The electrical conductivity of Pt-SZY and Pt-SCYb measured at 800°C under 1% H2 and air atmospheres revealed a reversible nanoionics phenomenon as a result of precipitation and dissolution of platinum nanoparticles. The electrical conductivity then decreases significantly when the atmosphere is change to hydrogen for Pt-SZY. In the case of Pt-SCYb an increase in the conductivity can be seen for the same changes of the atmosphere. This change in electrical conductivity has been explained by the effect of precipitated Pt particles. In addition, from the current interruption method using Pt as the electrode on SZY and SCYb electrolyte, the electrode overvoltage significantly increases after applying a small current on Pt/SZY/Pt cell. On the other hand the electrode overvoltage drops when SCYb electrolyte is used in the same system. This indicates that a high resistance layer is formed at the Pt/SZY interface, which is related to the decrease of the electrical conductivity under 1% H2 in the four prove method. In my presentation, we discuss these results together with the electrochemical characteristics of the Pt/oxide interface with proton conductive oxide.

Event date： 2017.3

Language：English   Presentation type：Oral presentation (general)  

Venue：首都大学東京　南大沢キャンパス（東京都八王子市南大沢1-1）   Country：Japan  

Event date： 2017.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：首都大学東京　南大沢キャンパス（東京都八王子市南大沢1-1）   Country：Japan  

Event date： 2017.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：首都大学東京　南大沢キャンパス（東京都八王子市南大沢1-1）   Country：Japan  

当研究室では、界面プロトン伝導性ナノ粒子を電解質として用いる水電解方式として「吸水多孔質電解質水電解」を提案し、検討を行ってきた。本研究では、アノード電極の触媒に関し開発を行い、チタン電極にイリジウムを電解メッキし、調製した酸化イリジウム電極の酸素発生側反応特性について検討した。測定はサイクリックボルタンメトリーによって行った。比較として白金担持カーボンよりも酸素発生反応のよい電極性能を確認した。

Event date： 2017.3

Language：Japanese  

Venue：首都大学東京　南大沢キャンパス（東京都八王子市南大沢1-1）   Country：Japan  

Event date： 2016.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Chiba   Country：Japan  

Proton-conducting electrolytes are an important and indispensable component of fuel cells and electrolyzers, governing the performance and to a large extent the design of the system. Oxides containing transition metals are commonly used as electrodes. During preparation and operation of the fuel cells, transition metals will diffuse from the electrodes to the electrolyte. A possible concern is that the diffusion of these transition metals will degrade the electrical conductivity of the electrolyte. There is a concern that the diffused transition metals will degrade the electrolyte conductivity. Shimura et al. reported significant decrease in the conductivity of BaCe0.9Y0.1O3-δ-based proton conductors on replacing partially Fe, Mn and Co for Ce [1]. In this study, the transition metal doping has been performed, i.e., AB0.9-xY0.1MxO3-δ (A = Ba and Sr, B = Zr and Ce, M = Co, Fe, Ni and Mn), and their electrical conduction and transport number properties were investigated to examine the effect of introducing transition metals to the proton conductor oxides.
The electrical conductivity and transport number change was observed by introducing transition metals. Especially, Ni-doped SCY and BCY were slightly changed than the un-doped original electrolytes. However, it has almost half of proton transport number at 600 oC in H2 atmosphere. These results suggest that the transition metal doping do cause changes in the ionic conductivity of the electrolytes from that of the original proton conductor and that the magnitude of the conductivity change depends on the transition metals and parent proton conductors.

Event date： 2016.12

Language：English  

Venue：Chiba   Country：Japan  

Ionic properties of metal oxides possibly changes in the vicinity of the interface with a hetero-phase material due to the formation of space charge layer and/or the strain originated from different coefficients of thermal expansion between the two materials, followed by the rearrangement of charge carriers [1]. In particular, the former case can be examined in a material with well dispersed second phase particles as an intriguing approach to alter the macroscopic properties [2]. This so-called nanoionics composite materials can be applied in energy conversion devices. In this work, we have examined and clarified the effects of homogeneously dispersed platinum nanoparticles on the proton conducting oxides.

Event date： 2016.12

Language：English  

Venue：Chiba   Country：Japan  

In this contribution, we present our resent findings on conductivity and stability of some perovskite-type proton conducting metal oxides and their application in steam electrolyzers cells at intermediate temperature. Starting from SrZr0.5Ce0.4Y0.1O3-δ (SZCY541), we examined the effects of Ba substitution for Sr and the doping level of Y on the lattice structure, electrical properties, as well as the proton content of the following compositions A(Zr5/9Ce4/9)1-xYxO3-δ, (A= Ba, Sr and x=0.1, 0.2). Cell terminal voltages, examined for thin film of (SZCY541) electrolyte on Ni-SZCY541 cathode substrates with Sr0.5Sm0.5CoO3 (SSC55) as anode gave a current density of 0.5 A cm-2 at an applied electrolysis voltage of 2 V. Whereas thin film of BZCY electrolyte gave a much improved performance at the same current density. On the electrode side, we show that some of the widely use electrode materials with acceptable electrode performance like SSC55 are not sufficiently durable against high steam concentration at 600 °C. Another issue is the inter-diffusion of transition metal species from the electrodes to the electrolyte causing the reduction of the proton conductivity.

Event date： 2016.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Rome   Country：Italy  

In the present contribution, we demonstrates our resent results on conductivity and stability of some perovskite-type proton conducting metal oxides and their application in steam electrolyzers cells at intermediate temperature. Starting from SrZr0.5Ce0.4Y0.1O3-δ (SZCY541), we examined the effects of Ba substitution for Sr and the doping level of Y on the lattice structure, electrical properties, as well as the proton content of the following compositions A(Zr5/9Ce4/9)1-xYxO3-δ, (A= Ba, Sr and x=0.1, 0.2). Cell terminal voltages, examined for thin film of (SZCY541) electrolyte on Ni-SZCY541 cathode substrates with Sr0.5Sm0.5CoO3 (SSC55) as anode gave a current density of 0.5 A cm-2 at an applied electrolysis voltage of 2 V. Whereas thin film of BZCY electrolyte gave a much improved performance at the same current density. On the electrode side, we show that some of the widely use electrode materials with acceptable electrode performance like SSC55 are not sufficiently durable against high steam concentration at 600 °C. Another issue is the inter-diffusion of transition metal species from the electrodes to the electrolyte causing the reduction of the proton conductivity.

Event date： 2016.10

Language：English  

Venue：Honolulu,Hawaii   Country：United States  

Nanoionics phenomenon in a Pt-containing proton-conducting oxide (Pt-r0.9Y0.1O3−α)
was demonstrated.

Other Link： https://ecs.confex.com/ecs/230/cfp.cgi

Event date： 2016.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Honolulu,Hawaii   Country：United States  

Steam electrolysis using proton-conducting electrolyte is reviewed. Present status and challenges including the issue of electronic leakage and transition metal diffusion between electrode and electrolyte are presented.

Other Link： https://ecs.confex.com/ecs/230/cfp.cgi

Event date： 2016.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Honolulu,Hawaii   Country：United States  

We have developed water electrolysis cell by use of a water absorbing porous electrolyte that works under similar conditions to a polymer electrolyte electrolysis cell. This cell consist of a surface-proton conducting metal oxide nanoparticles as proton-conducting electrolyte, a controlled-hydrophobic electrocatalytic layer, and fully hydrophobic gas diffusion layer. In this presentation, we will show that the hydrogen gas generation rate depend on the supplied water pressure by water electrolysis.

Other Link： https://ecs.confex.com/ecs/230/cfp.cgi

Event date： 2016.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Honolulu,Hawaii   Country：United States  

Chemically Stable proton conducting BZCY(54)8/9-2 has been developed as a promising proton conducting electrolytes for intermediate temperature BZCY(54)8/9-2 retained a high proton conductivity of 1.44 × 10-2 Scm-1 in wet 1 % H2 at 600° C as well as sufficient chemical stability under 80 % steam for 200 hours. Steam electrolysis using SZCY541 and as electrolytes was also investigated. BZCY(54)8/9-2 was most effective in reducing the cell over potential in the examined devices.

Other Link： https://ecs.confex.com/ecs/230/cfp.cgi

Event date： 2016.10

Language：English  

Venue：Honolulu,Hawaii   Country：United States  

In this study, we examined the device for separating only hydrogen by steam eforming of methane using a proton conductor cell.

Other Link： https://ecs.confex.com/ecs/230/cfp.cgi

Event date： 2016.10

Language：English  

Venue：Honolulu,Hawaii   Country：United States  

Proton-conducting oxides have been studied as intermediate-temperature electrolyte materials for fuel cells and steam electrolysis.

Other Link： https://ecs.confex.com/ecs/230/cfp.cgi

Event date： 2016.9

Language：Japanese  

Venue：鹿児島県指宿市   Country：Japan  

当研究室では、これまでにプロトン伝導性酸化物であるSrZr0.9Y0.1O3-δ（以下、SZY）中にナノサイズのPt粒子を析出させると、ナノイオニクス効果により電気伝導度が著しく低下することを報告している。本研究では、プロトン伝導性酸化物であるSrCe0.95Yb0.05O3-δ（SCYb）に着目し、Ptの固溶/析出によるイオン伝導機構の変化や、界面におけるナノイオニクスのメカニズムを明らかにすることを目的とした。

Event date： 2016.9

Language：English   Presentation type：Oral presentation (general)  

Venue：鹿児島県指宿市   Country：Japan  

Dense protonic electrolytes materials with the formula A(Zr5/9Ce4/9)1-xYxO3-δ, (A= Ba, Sr and x=0.1, 0.2) were obtained via chemical solution approach BZCY(54)8/92 showed a maximum proton occupancy of 17.1 mol % at 100 °C and retained the highest protonic conductivity of 1.44 × 10-2 Scm-1 in wet 1 % H2 at 600 °C as well as sufficient stability under 80 % steam. Proton occupancy is the major driving force for the high conductivity in the materials.

Event date： 2016.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鹿児島県指宿市   Country：Japan  

吸水多孔質水電解セルの開発状況について発表する。本セルで必要な要素であるガス拡散層と電極層と電解質層の調整方法と性能評価について説明した。
また、各要素を組み合わせて本セルを作動した時の水電解試験の結果についても説明した。加圧供給水の圧力の値に対し、水素発生量が変化することが明らかになった。このことから、本セルで想定していた原理通りに作動していることが判明した。

Event date： 2016.9

Language：English  

Venue：Oslo, Norway   Country：Other  

dense yttrium doped solid solutions of barium cerate, strontium cerate and zirconate with the formula A(Zr5/9Ce4/9)1-xYxO3-δ, (A= Ba, Sr and x=0.1, 0.2) were prepared and studied as potential proton conducting electrolytes for intermediate temperature peration. The transport properties of the sintered pellets were examined by AC impedance spectroscopy using porous platinum, silver and silver palladium paste as electrode respectively. The de-convoluted bulk, and grain boundary conductivity from the respective electrodes were obtained and compared. The bulk and grain boundary contributions were easily discernable in the impedance spectra of the studied compositions when porous platinum is used as electrode relative to silver electrode.

Event date： 2016.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Oslo, Norway   Country：Other  

プロトン伝導性酸化物に遷移金属が固溶したときの影響を調べた。遷移金属の固溶により、多くの場合にプロトン伝導性が低下した。電気化学セルを構成した場合に、電解質抵抗だけでなく電極反応にも影響を及ぼした。

Event date： 2016.9

Language：English  

Venue：Oslo, Norway   Country：Other  

ある種の金属酸化物であるプロトン伝導体は固体酸化物燃料電池の電解質に応用が期待されている。プロトン伝導は酸素空孔に水が水和した結果として理解されている。今回、それを高温と乾燥水素に曝したところ、これまで観測されたことの無い電気伝導度が得られた。その電気伝導度が得られた条件を模した、水素濃淡電池による起電力測定により、同一方向の起電力が観測された。この起電力から、伝導種は水素が供給したプロトンの可能性が示唆された。

Event date： 2016.9

Language：Japanese  

Venue：山口県山口市   Country：Japan  

固体高分子型燃料電池に用いられているNafion®等のパーフルオロスルホン酸膜は低温域における電気伝導度は高いが、機械的強度や熱安定性が低く使用可能な条件が限られるため代替材料の開発が求められている。本研究室では酸化チタン粒子の表面上に硫酸修飾を施した含水酸化チタンを作成し、Nafion®と同等の導電率を達成した。しかし、この材料は水中にて粒子表面の硫酸基が脱離し、時間経過と共に導電率の減衰、水の酸性化が起こることが判明した。[1]そこでチタン－リン酸系複合酸化物が作成され、含水酸化チタンに比べ導電率は劣るが酸溶出を抑制されたプロトン伝導体を得た。本研究では複合酸化物の粒子内部にもプロトン伝導手が存在することに着目し、解砕による伝導手の増加つまりは微粒子化による導電率の向上について検討を行った。

Event date： 2016.9

Language：Japanese  

Venue：山口県山口市   Country：Japan  

固体酸化物形燃料電池（SOFC）の高性能化には電極の微細化による電極過電圧の低減が有効とされている。そこで、典型的なSOFC用カソード材料のLa0.6Sr0.4Co0.2Fe0.8O3-δ（LSCF6428）を対象に、粉砕機AまたはBを用いたビーズミル法による試料の微細化を検討した。EtOH溶媒のLSCF6428スラリー（濃度2.5wt%）を調製して、粉砕機Aを用いて1h、2h、3h、4h粉砕、または粉砕機Bを使用して7h粉砕した。結果、LSCF6428を約50~60nm程度まで粉砕することに成功した。

Event date： 2016.8

Language：Japanese  

Venue：福岡県太宰府市　ルートイングランティア太宰府   Country：Japan  

Event date： 2016.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Sapporp Hokkaido Japan   Country：Japan  

Event date： 2016.6

Language：English  

Venue：Sapporp Hokkaido Japan   Country：Japan  

It is essential for hydration reaction in proton conductor to introduce water molecule. At present, unexpected conductivity with proton conductor was observed in dry hydrogen. It seems that this proton conductor had proton conduction in the atmosphere.

Event date： 2016.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Jeju island   Country：Korea, Republic of  

A “water-absorbing porous electrolyte cell” is proposed and demonstrated as a method of water electrolysis that will play an important role for the production of renewable hydrogen. Materials and the water electrolysis characteristics is reported.

Event date： 2016.2

Language：English  

Venue：熊本   Country：Japan  

Event date： 2016.2

Language：English  

Venue：I2CNER第１研究棟   Country：Japan  

Water-absorbing porous electrolyte cell consists of a surface-proton conducting metal oxide nanoparticles, controlled-hydrophobic catalytic layers and fully hydrophobic and gas diffusion layers. (1) electrolyte, (2) gas diffusion layer, and (3) electrode parts of the cell are the research subjects, so that the investigations are also contributing to Project 1 Electrodes and Project 2 Electrolyte.

Other Link： http://i2cner.kyushu-u.ac.jp/en/

Event date： 2016.2

Language：English  

Venue：I2CNER第１研究棟   Country：Japan  

Design and synthesize highly durable compactible electrode materials and the fabrication of ultra-thin electrolytes (≤ 20μm) materials using microfabrication techniques for advance SPECs and SPFCs devices
Convenient production of dry and fairly pure hydrogen without additional gas separation systems, in comparison to oxygen ionic conductor

Other Link： http://i2cner.kyushu-u.ac.jp/en/

Event date： 2016.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：アバンセ，グランデはがくれ（佐賀市）   Country：Japan  

Event date： 2015.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：札幌　北海道大学   Country：Japan  

Titanium phosphate nanoparticle (Ti-P) prepared by sol-gel method was characterized by FT-IR, and XRD measurements, and evaluated by electrical conductivity and acid dissolution tests. We confirmed that the obtained Ti-P was consisted of Ti-O-P structure and showed an electrical conductivity value of 10-3 S cm-1 and less acid dissolution than that of previous sulfuric acid modified nanoparticle.

Event date： 2015.11

Language：English   Presentation type：Oral presentation (general)  

Venue：札幌　北海道大学   Country：Japan  

The present work demonstrates nanoionics effects using SrCe0.95Yb0.05O3−δ. and SrZr0.9Y0.1O3−δ as the major matrix phases and platinum metal nanoparticles as the minor dispersed phase. The platinum phase was introduced via the combustion synthesis approach and sintered at 1100 o C, resulting in solid solutions with platinum in the perovskite lattice. A reversible nanoionics phenomenon is observed under reducing and oxidizing atmospheres as a result of platinum nanoparticles precipitation.

Event date： 2015.10

Language：Japanese  

Venue：東京都江戸川区タワーホール船橋   Country：Japan  

SrZrO3等の金属酸化物中においては高温で、プロトンによる伝導性が観測される。雰囲気中の水蒸気が格子中に取り込まれることでプロトン伝導性が発現すると考えられている[1]。銭谷らは乾燥水素中において、薄膜状のBaZr1-yYxO3-δが通常よりも高い電気伝導度を持つと報告した[2]。本研究では、SrZr0.9Y0.1O3-δ（以下、SZY91と略す）のバルク体に注目し、乾燥水素中における電気伝導度について検討した。

Event date： 2015.10

Language：English   Presentation type：Symposium, workshop panel (public)  

Venue：Sydney   Country：Australia  

Hydrogen is considered as a secondary energy and can be used as an energy carier to help address concerns about energy security and global climate change. Hydrogen can be carbon-neutral when it is produced from renewable energies, such as solar and wind energy. Water electrolysis is a means to convert electricity to hydrogen. There are several types of water electrolysis with both merit and demerit. In this paper, a “water-absorbing porous electrolyte cell” (Fig. 1 a) is propsed and demonstrated as a method of water electrolysis. Materials and the water electrolysis characteristics are introduced and discussed.
Proton conduction on an acid-modified surface metal oxide nanoparticles is employed as the electrolyte (Fig. 1 b). The interior portion of the particles is insulating whereas the surface is utilized as a proton conduction pathway (Fig. 1 c). Particle size reduction resulted in a high surface area and hence a large proton conducting surface. The authors have found so far that sulfonated titania nanoparticles prepaired via thermal decomposition of titanyl sulfate show high proton conduction in both water and humid atmosphere [1].

Event date： 2015.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Columbus, Ohio   Country：United States  

Y-doped A(Zr,Ce)O3, at Zr/Ce=5/4 with A being either Ba or r has been studied as a potential proton conducting electrolyte. The effects of Ba substitution for r and Y doping level on the lattice structure, proton content, electrical properties, hydration behavior, as well as chemical stability are investigated. Thermo-gravimetric analyses revealed a similar proton concentration in both 10％ and 20% Y doping cases for A=r, resulting in almost comparable proton conductivities in both wet hydrogen and oxygen atmosphere. When A=Ba, Y doping level of 20% results in higher conductivity than the 10% Y doped case. These results suggest that Ba and r at A-site have different effects on hydration and proton mobility.

Event date： 2015.9

Language：English  

Venue：埼玉工業大学（埼玉県深谷市普済寺1690）   Country：Japan  

Event date： 2015.9

Language：Japanese  

Venue：埼玉工業大学（埼玉県深谷市普済寺1690）   Country：Japan  

固体高分子(PEM)水電解に使用する固体電解質としてスルホン酸基を有するフッ素系高分子が用いられて いる。その一つとしてナフィオンが使用されているが熱安定性が低く・装置のコストが高くなる等の課題が あるため代替材料の開発が求められている。本研究室ではセラミックスナノ粒子表面を伝導場とするプロト ン伝導性ナノ粒子の研究開発を進めており、硫酸修飾ナノチタニアが高いプロトン伝導性を有していること を明らかにしている。(1)しかしながら、水中下においてチタン粒子表面のスルホン酸基の脱離が起こりやす いため、プロトン伝導性が低下し水電解を長期間作動できない問題がある。本研究では問題解決のためリン 酸修飾ナノチタニア(Ti-P)に着目し、水電解への応用を検討した。リン酸基はスルホン酸基と比較してチタン との結合が強いため酸性基の脱離が抑制されることが期待される。本発表では Ti-P の調製方法と評価結果（プ ロトン伝導性と酸性基の経時変化）および水電解実験の結果について報告を行う。

Event date： 2015.9

Language：Japanese  

Venue：北海道ニセコ町   Country：Japan  

Event date： 2015.9

Language：Japanese  

Venue：志賀島(福岡県)   Country：Japan  

固体高分子(PEM)水電解に使用する固体電解質としてスルホン酸基を有するフッ素系高分子が用いられている。その一つとしてナフィオンが使用されているが熱安定性が低く・装置のコストが高くなる等の課題があるため代替材料の開発が求められている。本研究室ではセラミックスナノ粒子表面を伝導場とするプロトン伝導性ナノ粒子の研究開発を進めており、硫酸修飾ナノチタニアが高いプロトン伝導性を有していることを明らかにしている。しかしながら、水中下においてチタン粒子表面のスルホン酸基の脱離が起こりやすいため、プロトン伝導性が低下し水電解を長期間作動できない問題がある。本研究では問題解決のためリン酸修飾ナノチタニア(Ti-P)に着目し、水電解への応用を検討した。リン酸基はスルホン酸基と比較してチタンとの結合が強いため酸性基の脱離が抑制されることが期待される。本発表ではTi-Pの調製方法と評価結果（プロトン伝導性と酸性基の経時変化）および水電解実験の結果について報告を行う。

Event date： 2015.8 - 2015.9

Language：Japanese  

Venue：伊豆熱川温泉　熱川ハイツ   Country：Japan  

固体高分子（PEM）水電解に使用する固体電解質としてスルホン酸基を有するフッ素系高分子が用いられている。その一つとしてナフィオンが使用されているが熱安定性が低く・装置のコストが高くなる等の課題があるため代替材料の開発が求められている。本研究室ではセラミックスナノ粒子表面を伝導場とするプロトン伝導性ナノ粒子の研究開発を進めており、硫酸修飾ナノチタニアが高いプロトン伝導性を有していることを明らかにしている(1)。しかしながら、水中においてチタン粒子表面のスルホン酸基の脱離が起こりやすいため、プロトン伝導性が低下し水電解を長期間作動できない問題がある。本研究では、リン酸修飾ナノチタニア(Ti-P)に着目し、水電解への応用を検討した。リン酸基はスルホン酸基と比較してチタンとの結合が強いため酸性基の脱離が抑制されることが期待される。本発表ではTi-Pの調製方法と評価結果（プロトン伝導性と酸性基の経時変化）および水電解実験の結果について報告を行う。

Event date： 2015.7

Language：English  

Venue：Bordeaux   Country：France  

A solid oxide fuel cell (SOFC) is an electrochemical energy conversion device that directly converts the chemical energy of fuel to electricity with high energy efficiency [1]. SOFC consists of two porous electrodes (cathode and anode) and a dense electrolyte. The performance of the device depends on the efficient movement of protons within it. Proton conductivity has been reported for many perovskites type oxides (ABO3) when doped with an aliovalent element in the B site and exposure in a humidified atmosphere. The humidified atmosphere is essential for the hydration process which ultimately provides the protons in the electrolyte [2].
In the present study we report an unpreceded conductivity of SrZr0.9Y0.1O3-δ(SZY91) electrolyte after exposure to dry hydrogen gas. The high conductivity is not explicable from conventional proton and electron conduction mechanism [3]. Therefore, a conduction mechanism observed is not well understood at this time. SZY91 which is replaced zirconium with yttrium by 10% compared to SrZO3 was prepared by a solid-state reaction method. Upon exposure to dry hydrogen gas at 900 oC the observed conductivity is as shown in figure 1. This figure indicates results of conductivity at different temperatures during heating and cooling in dry hydrogen gas. According to these results,novel proton conduction may be the reason for the change in conduction.

Event date： 2015.7

Language：English  

Venue：Bordeaux   Country：France  

Proton conductor can be used as electrolytes for fuel cells and electrolyzers. Solid electrolytes are the most important and indispensable component of fuel cells and electrolyzers, governing the performance and to a large extent the design of the system. Oxides containing transition metals are commonly used as electrodes. During preparation and operation of the fuel cells, transition metals will diffuse from the electrodes to the electrolyte. There is a concern that the diffused transition metals will degrade the electrolyte conductivity. Shimura et al. reported significant decrease in the conductivity of BaCe0.9Y0.1O3-δ-based proton conductors on replacing partially Fe, Mn and Co for Ce [1]. In this study, the transition metal doping has been performed, i.e., AB0.9-xY0.1MxO3-δ (A = Ba and Sr, B = Zr and Ce, M = Co, Fe, Ni and Mn), and their electrical conduction properties were investigated to examine the effect of introducing transition metals to the proton conductor oxides. AB0.9-xY0.1MxO3-δ (SZYM, SCYM, BCYM and BZYM) were prepared by a solid-state reaction method. Phase identification was carried out by X-ray diffraction. The conductivity was measured by a four-terminal AC impedance method. The electrical conductivity change was observed by introducing transition metals. These results suggest that the introduction of transition metals causes the change in the conductivity of the proton conducting electrolytes in most cases, and that the change in the conductivity depends on the sort of transition metals. This means that the impact of introducing transition metals to the electrical conduction properties depends on the oxide. The above two cases suggests that either A-site (Sr or Ba) or B-site (Ce or Zr) possibly governs for the impact of conductivity is sensitive to the transition metals.

Event date： 2015.7

Language：English  

Venue：一橋大学一橋講堂（東京・竹橋）   Country：Japan  

Other Link： http://www.jaci4gsc7.org/1st_circular/

Event date： 2015.6

Language：Japanese  

Venue：北九州国際会議場（北九州市小倉北区浅野3-9-30）   Country：Japan  

SrZr0.9Y0.1O3-α(SZY91)でプロトンが伝導するには水蒸気雰囲気が必須とされてきた。水蒸気分圧が決まらない、乾燥水素中でSZY91に新たな電気伝導が発現した。この原因として、従来とは異なるプロトンの伝導機構がある可能性が示唆された。

Event date： 2015.6

Language：English  

Venue：北九州国際会議場（北九州市小倉北区浅野3-9-30）   Country：Japan  

The present work, we demonstrate nanoionics effects using SrCe0.95Yb0.05O3−α. and SrZr0.9Y0.1O3−α as the major matrix phase and platinum metal nanoparticles as the minor dispersed phase. A reversible nanoionics phenomenon is observed under reducing and oxidizing atmospheres as a result of platinum nanoparticles precipitation.

Event date： 2015.6

Language：Japanese  

Venue：北九州国際会議場（北九州市小倉北区浅野3-9-30）   Country：Japan  

持続可能な低エネルギー社会の構築に向けて、固体酸化物燃料電池（SOFC）は効率の高いエネルギー変換デバイスと して有用であり、その高性能化が重要な課題である。多孔性ガス電極はSOFCのもっとも重要な構成要素の一つであり、 特に低温作動化に向けて、電極過電圧を低減できる高性能多孔性ガス電極の開発が求められている。電極反応は、 燃料や酸素などの気体が電極および電解質と電子やイオンを授受することで進行し、その高性能化には、構造の 微細化が有効である。我々はこれまでに遊星ミルと微小のビーズ状の粉砕媒体（~0.05mmΦ）を組み合わせた 「遊星ビーズミリング」により、種々の酸化物材料がシングルナノサイズ（~2nm）まで粉砕できる事を見出した[1]。 本研究では「遊星ビーズミリング」を固体酸化物燃料電池の電極原料の微細化に適用し、ナノ多孔質構造を有する 電極の調整とその電極特性について検討した。

Event date： 2015.6

Language：Japanese  

Venue：北九州国際会議場（北九州市小倉北区浅野3-9-30）   Country：Japan  

Event date： 2015.6

Language：English  

Venue：北九州国際会議場（北九州市小倉北区浅野3-9-30）   Country：Japan  

The effect of the presence of transition metal at the B site of the proton conducting perovskites type oxide has been investigated. AB0.85Y0.1MxO3-δ (A=Ba, Sr, B=Ce, Zr, M = Co, Fe, Ni, Mn) was prepared and their electrochemical behavior in oxidative and reducing atmospheres examined. The electrical conductivity varies, decreasing in most cases, upon the introduction of the transition metals and the changes take place in different ways depending on A-site or B-site as well as the atmospheres.

Event date： 2015.6

Language：English  

Venue：Keystone Resort & Conference Center   Country：United States  

Proton conductivity of Ti-P-O complex oxide nanoparticles in water has been investigated, assuming the use as an electrolyte material for water electrolysis. Most of the solid ion conductor is crystalline and ionic defects works as charge carriers, so that relatively high temperature is necessary for the ionic conduction. Surface of the solid can work another type of the ion conduction field and nanoparticles equipped with large surface area can be ion conduction media, with examples of ceria nanoparticles and acid-modified metal oxides. In this work proton incorporated on the surface of Ti-P oxide nanoparticles in the form of hydroxyl group is assumed as a charge carrier and its conductivity with a help of liquid water is considered. The Ti-P oxide particles were prepared via a wet chemical method using titanium alkoxide and phosphoric acid. Resulting precipitates are washed dried and compacted in a disk or bar shape and electrical conductivity in water was measured. Dissolution of phosphoric acid into water was evaluated by measuring the pH. The conductivity and the dissolution tendency depends largely on the heat treatment and the ratip of Ti/P. Infrared absorption measurement reveals the P=O double bond and Ti-O-P bond, with existence of OH group part of which can be assumed to work as a source of protonic charge carrier.

Other Link： http://www.mrs.org/ssi-20/

Event date： 2015.6

Language：English  

Venue：Keystone Resort & Conference Center   Country：United States  

Ionic conductivity is an important transport process for all electrochemical energy conversion and storage devices and very relevant for a sustainable energy economy. In the present work Yttria-doped strontium zirconate partially substitted with ceria SrZr0.5Ce0.4Y0.1O3-α (SZCY541) have been studied as a potential proton conducting electrolyte for intermediate temperature steam electrolysis. The effects of Ba substitution for Sr on the lattice structure, proton content, electrical properties, hydration behavior, as well as chemical stability are investigated. Proton content was examined by tailoring dopant concentration to improve the proton conductivity. Thermo-gravimetric analyses revealed a similar proton concentration in both SZCY541 and SrZr0.44Ce0.35Y0.2O3-α (SZCY542) with a constant Zr/Ce fraction of 5:4. Both samples showed almost comparable proton conductivities in both wet hydrogen and oxygen atmosphere. Whereas BaZr0.44Ce0.35Y0.2O3-α (BZCY542) showed a higher proton mobility than BaZr0.5Ce0.4Y0.1O3-α (BZCY541) and retained the highest proton conductivity of 1.44 × 10-2 Scm-1 in wet 1 % H2 at 600 o　C as well as excellent chemical stability under 80 % steam for 200 hours. These results suggest Ba and Sr at A-site have different effects on hydration and proton mobility. This paper discusses these aspects based on experimental results as well as steam electrolysis using SZCY-541 and BZCY542 as electrolytes.

Other Link： http://www.mrs.org/ssi-20/

Event date： 2015.5

Language：English   Presentation type：Oral presentation (general)  

Venue：東京   Country：Japan  

Other Link： http://injapan.no/energy2015-day2/

Event date： 2015.5

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：第32回希土類討論会   Country：Japan  

Event date： 2015.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山大学   Country：Japan  

Event date： 2014.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡県大野城市 大野城まどかぴあ   Country：Japan  

Event date： 2014.9

Language：English  

Venue：Seoul   Country：Korea, Republic of  

Other Link： http://www.sspc17.org/main/

Event date： 2014.9

Language：English  

Venue：Seoul   Country：Korea, Republic of  

Other Link： http://www.sspc17.org/main/

Event date： 2014.9

Language：English  

Venue：Seoul   Country：Korea, Republic of  

Other Link： http://www.sspc17.org/main/

Event date： 2014.9

Language：English  

Venue：Seoul   Country：Korea, Republic of  

Other Link： http://www.sspc17.org/main/

Event date： 2014.9

Language：Japanese  

Venue：鹿児島大学   Country：Japan  

Event date： 2014.9

Language：English  

Venue：岐阜県 下呂温泉 木曽屋   Country：Japan  

Event date： 2014.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鞆シーサイドホテル(広島県福山市鞆町鞆 555)   Country：Japan  

Event date： 2014.6

Language：Japanese  

Venue：北九州国際会議場   Country：Japan  

Event date： 2014.6

Language：English  

Venue：北九州国際会議場   Country：Japan  

Event date： 2014.6

Language：Japanese  

Venue：北九州国際会議場   Country：Japan  

Event date： 2014.6

Language：English  

Country：Italy  

Event date： 2014.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋市   Country：Japan  

Hiroshige Matsumoto, Intermediate temperature steam electrolysis using proton-conducting oxide, 94th Annual Meeting of the Chemical Society of Japan, 28th Mar, Nagoya, Japan

Event date： 2014.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都   Country：Japan  

Hiroshige Matsumoto, Novel nano-surface proton conductor and application to hydrogen production via water electrolysis, COI-Forum(COI STREAM), 13rd Mar, Tokyo, Japan

Event date： 2014.2

Language：English  

Venue：Fukuoka   Country：Japan  

Event date： 2013.11

Language：English  

Venue：Kitakyushu   Country：Japan  

Event date： 2013.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本市   Country：Japan  

Event date： 2013.11

Language：English   Presentation type：Oral presentation (general)  

Venue：熊本市   Country：Japan  

Event date： 2013.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡市   Country：Japan  

Hiroshige Matsumoto, Science and technology for environment, the lecture on Engineering Academy of Japan, Kyushu branch, 18th Oct, Fukuoka, Japan

Event date： 2013.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都   Country：Japan  

Hiroyuki Oda, Takehiro Yoneda, Yuji Okuyama, Takaaki, Nanostructure electrodes prepared via planetary bead-milling and use for PCFC, Annual Meeting of the Electrochemical Society of Japan(Fall, 2013), 27th Sep, Tokyo, Japan

Event date： 2013.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都   Country：Japan  

LeeYoung-Sung,HatadaNaoyuki,OkuyamaYuji and MatsumotoHiroshige, Effect of transition metal doping on the electrical properties of proton conducting perovskites, Annual Meeting of the Electrochemical Society of Japan(Fall, 2013), 27th Sep, Tokyo, Japan

Event date： 2013.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Cleveland   Country：United States  

Event date： 2013.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Fukuoka   Country：Japan  

Event date： 2013.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Montpellier   Country：France  

Event date： 2013.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北九州市   Country：Japan  

Kaori Isa, Yuji Okuyama, Takaaki Sakai and Hiroshige Matsumoto, Development of electrochemical hydrogen production devices using a La-based proton conducting oxide, The 50th joint meeting of chemical branches in Kyushu, 6th July, Kiyakyushu, Japan

Event date： 2013.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北九州市   Country：Japan  

Takehiro Yoneda, Yuji Okuyama and Hiroshige Matsumoto, Proton solubility and electrical properties of BaCe0.8-xZrxY0.2O3-δ, The 50th joint meeting of chemical branches in Kyushu, 6th July, Kitakyushu Japan

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Kyoto   Country：Japan  

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Kyoto   Country：Japan  

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Kyoto   Country：Japan  

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Kyoto   Country：Japan  

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Kyoto   Country：Japan  

Event date： 2012.3

Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2012.3

Presentation type：Oral presentation (invited, special)  

Venue：浜松市   Country：Japan  

Event date： 2012.3

Presentation type：Oral presentation (general)  

Venue：浜松市   Country：Japan  

Event date： 2012.3

Presentation type：Oral presentation (general)  

Venue：浜松市   Country：Japan  

Event date： 2012.2

Venue：福岡市   Country：Japan  

Event date： 2012.1

Presentation type：Oral presentation (general)  

Venue：東京都   Country：Japan  

Event date： 2012.1

Presentation type：Oral presentation (general)  

Venue：東京都   Country：Japan  

Event date： 2011.12

Presentation type：Oral presentation (general)  

Venue：鳥取市   Country：Japan  

Event date： 2011.12

Presentation type：Oral presentation (general)  

Venue：福岡市   Country：Japan  

Event date： 2011.12

Presentation type：Oral presentation (invited, special)  

Country：Japan  

Event date： 2011.11

Presentation type：Oral presentation (general)  

Venue：宜野湾市   Country：Japan  

Event date： 2011.11

Presentation type：Oral presentation (invited, special)  

Venue：Montpellier   Country：France  

Event date： 2011.9

Presentation type：Oral presentation (general)  

Venue：札幌市   Country：Japan  

Event date： 2011.9

Venue：氷見市   Country：Japan  

Event date： 2011.7

Venue：北九州市   Country：Japan  

Event date： 2011.7 - 2012.7

Venue：Warsaw   Country：Poland  

Event date： 2011.4

Venue：北九州市   Country：Japan  

Event date： 2011.4

Venue：北九州市   Country：Japan  

Event date： 2011.4

Presentation type：Oral presentation (invited, special)  

Venue：Daegu   Country：Korea, Republic of  

Event date： 2011.3

Presentation type：Oral presentation (general)  

Venue：神奈川   Country：Japan  

Event date： 2011.3

Presentation type：Oral presentation (general)  

Venue：神奈川   Country：Japan  

Event date： 2011.3

Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2010.11

Presentation type：Oral presentation (general)  

Venue：青森   Country：Japan  

Event date： 2010.11

Presentation type：Oral presentation (general)  

Venue：青森   Country：Japan  

Event date： 2010.11

Presentation type：Oral presentation (general)  

Venue：青森   Country：Japan  

Event date： 2010.11

Presentation type：Oral presentation (general)  

Venue：熊本   Country：Japan  

Event date： 2010.11

Presentation type：Oral presentation (general)  

Venue：熊本   Country：Japan  

Event date： 2010.9

Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Event date： 2010.9

Presentation type：Oral presentation (general)  

Venue：神奈川   Country：Japan  

Event date： 2010.8 - 2011.8

Presentation type：Oral presentation (general)  

Venue：California   Country：United States  

Event date： 2010.7

Venue：北九州   Country：Japan  

Event date： 2010.7

Venue：北九州   Country：Japan  

Event date： 2010.6

Presentation type：Oral presentation (general)  

Venue：神奈川   Country：Japan  

Event date： 2010.5

Presentation type：Oral presentation (general)  

Venue：熊本   Country：Japan  

Event date： 2010.5

Venue：熊本   Country：Japan  

Event date： 2010.3

Venue：東京   Country：Japan  

Event date： 2010.3

Venue：富山   Country：Japan  

Event date： 2010.3

Venue：富山   Country：Japan  

Event date： 2010.1

Venue：沖縄   Country：Japan  

Event date： 2010.1

Venue：沖縄   Country：Japan  

Event date： 2009.12

Venue：沖縄   Country：Japan  

Event date： 2009.12

Venue：大阪   Country：Japan  

Event date： 2009.12

Venue：大阪   Country：Japan  

Event date： 2009.11

Venue：愛媛   Country：Japan  

Event date： 2009.11

Venue：愛媛   Country：Japan  

Event date： 2009.11

Venue：愛媛   Country：Japan  

Event date： 2009.7

Venue：北九州   Country：Japan  

Event date： 2009.7

Venue：北九州   Country：Japan  

Event date： 2009.7

Venue：北九州   Country：Japan  

Event date： 2009.7

Venue：北九州   Country：Japan  

Event date： 2009.7

Venue：北九州   Country：Japan  

Event date： 2009.7

Venue：北九州   Country：Japan  

Event date： 2009.6

Venue：Toronto   Country：Canada  

Event date： 2009.6

Venue：Toronto   Country：Canada  

Event date： 2009.6

Venue：Singapore   Country：Singapore  

Event date： 2009.5

Venue：札幌   Country：Japan  

Event date： 2008.6

Venue：Denver Colorado   Country：United States  

Event date： 2008.6

Venue：Yonsei University   Country：Korea, Republic of  

Event date： 2008.5

Venue：Arizona, Phoenix Convention Center   Country：Other  

Event date： 2008.5

Venue：Phoenix, Arizona, Phoenix Convention Center   Country：Other  

Event date： 2008.5

Venue：Taipei   Country：Other  

Event date： 2008.3 - 2008.7

Venue：東京都江戸川区タワーホール船堀   Country：Japan  

Event date： 2008.3

Venue：東京都江戸川区タワーホール船堀   Country：Japan  

Event date： 2008.3

Venue：東京都江戸川区タワーホール船堀   Country：Japan  

Event date： 2008.3

Venue：立教大学池袋キャンパス   Country：Japan  

Event date： 2008.3

Venue：立教大学池袋キャンパス   Country：Japan  

Event date： 2008.3

Venue：立教大学池袋キャンパス   Country：Japan  

Event date： 2008.3

Venue：立教大学池袋キャンパス   Country：Japan  

Event date： 2008.3

Venue：立教大学池袋キャンパス   Country：Japan  

Event date： 2008.3

Venue：立教大学池袋キャンパス   Country：Japan  

Event date： 2008.1

Venue：Changwon Exhibition Convention Center(CECO)   Country：Korea, Republic of  

Event date： 2008.1

Venue：Changwon Exhibition Convention Center(CECO)   Country：Korea, Republic of  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都港   Country：Japan  

Venue：東京理科大学理学部   Country：Japan  

Venue：東京理科大学理学部   Country：Japan  

Venue：New Public Hall, Nara   Country：Japan  

Venue：Nara New Public   Country：Japan  

Venue：Shanghai Worldfield Convention Hotel   Country：China  

Venue：Shanghai Worldfield Convention Hotel   Country：China  

Venue：Shanghai Worldfield Convention Hotel   Country：China  

Venue：Shanghai Worldfield Convention Hotel   Country：China  

Venue：Shanghai Worldfield Convention Hotel   Country：China  

Venue：札幌コンベンションセンター   Country：Japan  

Venue：北海道大学   Country：Japan  

Venue：北海道大学   Country：Japan  

Venue：北海道大学   Country：Japan  

Venue：北海道大学   Country：Japan  

Venue：北海道大学   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：北海道大学   Country：Japan  

Venue：北海道大学   Country：Japan  

Venue：東京工業大学   Country：Japan  

Venue：東京工業大学   Country：Japan  

Venue：東京工業大学   Country：Japan  

Venue：東京工業大学   Country：Japan  

Venue：東京工業大学   Country：Japan  

Venue：Yufuin-Nanairo no Kaze   Country：Japan  

Venue：札幌コンベンションセンター   Country：Japan  

Venue：札幌コンベンションセンター   Country：Japan