Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
HIROSHIGE MATSUMOTO Last modified date:2018.03.23

Professor / Electrochemical Energy Conversion Division / International Institute for Carbon-Neutral Energy Research


Papers
1. Kwati Leonard, John Druce, Vincent Thoréton, J. A. Kilner, Hiroshige Matsumoto, Exploring mixed proton/electron conducting air electrode materials in protonic electrolysis cell, Solid State Ionics, 10.1016/j.ssi.2018.02.016, 319, 218-222, 2018.06, 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..
2. Masamichi Nishihara, Yuki Terayama, Takamasa Haji, Stephen Matthew Lyth, Shigeo Satokawa, Hiroshige Matsumoto, Proton-conductive nano zeolite-PVA composite film as a new water-absorbing electrolyte for water electrolysis, Express Polymer Letters, 10.3144/expresspolymlett.2018.23, 12, 3, 256-264, 2018.03, 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..
3. Jing Yuhang, Hiroshiae Matsumoto, Alum Narayana R., Mechanistic Insights into Hydration of Solid Oxides, Chemistry of Materials, 10.1021/acs.chemmater.7b03476, 30, 1, 138-144, 2018.01, 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..
4. Young-Sung Lee, Yasuhiro Takamura, Yi-Hsuan Lee, Kwati Leonard, Hiroshige Matsumoto, Investigation of the Electrical Properties in Indium and Yttrium-Doped Barium Zirconate Based Proton Conducting Perovskites, Material Transactions, doi:10.2320/matertrans.MB201702, 59, 1, 19-22, 2017.12, 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..
5. Takaaki Somekawa, Yoshio Matsuzaki, Mariko Sugahara, Hiroshige Matsumoto, Shunsuke Taniguchi, Kazunari Sasaki, Physicochemical properties of Ba(Zr,Ce)O3-δ-based proton-conducting electrolytes for solid oxide fuel cells in terms of chemical stability and electrochemical performance, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2017.04.267, 42, 26, 16722-16730, 2017.06, 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..
6. Hiroshige Matsumoto, Yoshio Matsuzaki, Yuya Tachikawa, Takaaki Somekawa, K. Sato, Yasuharu Kawabata, Mariko Sugahara, Shunsuke Taniguchi, Kazunari SASAKI, Relationship between electrochemical properties and electrolyte partial conductivities of proton-conducting ceramic fuel cells, ECS Transactions, 10.1149/07801.0441ecst , 78, 1, 441-450, 2017.05, 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..
7. Jinda Yeyongchaiwat, Hiroshige Matsumoto, Tatsumi Ishihara, Oxidative reforming of propane with oxygen permeating membrane
reactor using Pr2Ni0.75Cu0.25Ga0.05O4 perovskite related mixed conductor, Solid State Ionics, 10.1016/j.ssi.2016.12.035, 301, 23-27, 2017.03, 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..
8. Hiroki Takahashi, Isamu Yashima, Koji Amezawa, Koichi Eguchi, Hiroshige Matsumoto, Hitoshi Takamura, Shu Yamaguchi, First-Principles Calculations for the Energetics of the Hydration Reaction of Acceptor-Doped BaZrO3, Chemistry of Materials, 10.1021/acs.chemmater.6b03907, 29, 4, 1518-1526, 2017.02, 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..
9. KWATI LEONARD, Lee Youngsung, Yuji Okuyama, Hiroshige Matsumoto, Influence of dopant levels on the hydration properties of SZCY and BZCY proton conducting ceramics for hydrogen production, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2016.10.120, 42, 7, 3296-3937, 2017.02, Dense yttrium doped solid solutions of alkaline earth cerate and zirconate with the formula A(Zr5/9Ce4/9)1−xYxO3−δ, (A = Sr and Ba, x = 0.1, 0.2) have been prepared and studied as potential proton conducting electrolytes. Thermo-gravimetric analysis was used to determine the proton concentration in the specimens. BZCY(54)8/92 showed a maximum proton concentration limit of 17.1 mol % compared to only 6.03 mol % for SZCY(54)8/92 and retained the highest proton conductivity of 1.44 × 10−2 S cm−1 in wet 1% H2 at 600 °C. Sufficient chemical stability under 80% steam for 200 h was confirm for the said composition. Approximately similar proton mobility levels were observed at 600 °C for the compositions. The major difference in total conductivity originates mostly from the differences in proton concentration levels. The bulk and grain boundary contributions on the conductivity were strongly dependent on the A-site host, with the grain boundary response being the main source of resistance in the BZCY specimens relative to the SZCY. © 2016 Hydrogen Energy Publications LLC.
10. Takaaki Somekawa, Yoshio Matsuzaki, Yuya Tachikawa, Hiroshige Matsumoto, Shunsuke Taniguchi, Kazunari Sasaki, Physicochemical properties of proton-conductive Ba(Zr0.1Ce0.7Y0.1Yb0.1)O3−δ solid electrolyte in terms of electrochemical performance of solid oxide fuel cells, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2016.07.265, 41, 39, 17539-17547, 2016.10, 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.
11. Yoshio Matsuzaki, Yuya Tachikawa, Takaaki Somekawa, Toru Hatae, Hiroshige Matsumoto, Shunsuke Taniguchi, Kazunari SASAKI, Effect of proton-conduction in electrolyte on electric efficiency of multi-stage solid oxide fuel cells, Scientific Reports, 10.1038/srep12640, 5, Article number 12640, 2015.07, 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)..
12. Takaaki Sakai, Keita Arakawa, Masako Ogushi, Tatsumi Ishihara, Hiroshige Matsumoto, Yuji Okuyama, Atmosphere dependence of anode reaction of intermediate temperature steam electrolysis using perovskite type proton conductor, Journal of Solid State Electrochemistry, 10.1007/s10008-015-2808-9, 19, 6, 1793-1798, 2015.03, 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..
13. Yuji Okuyama, Kaori Isa, Youngsung Lee, Takaaki Sakai, Hiroshige Matsumoto, Incorporation and conduction of proton in SrCe0.9 - XZrxY0.1O3 - δ, Solid State Ionics, 10.1016/j.ssi.2015.01.010, 275, 35-38, 2015.07, 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..
14. Yoshio Matsuzaki, Yuya Tachikawa, T. Hatae, Hiroshige Matsumoto, Shunsuke Taniguchi, Kazunari Sasaki, A parametric study of SOFC performances with multi-stage electrochemical oxidation for enhancement of electric efficiency, ECS Transactions, 10.1149/06801.1961ecst, 68, 1, 1961-1968, 2015.07, 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..
15. Yuji Okuyama, Kenji Okuyama, Yasunobu Mizutani, Takaaki Sakai, Youngsung Lee, Hiroshige Matsumoto, Proton transport properties of La0.9Sr0.1Yb0.8In0.2O3-δ and its application to proton ceramic fuel cell, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2014.06.113, 39, 35, 20829-20836, 2014.12, 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..
16. Yuji Okuyama, Shohei Ikeda, Takaaki Sakai, Hiroshige Matsumoto, Incorporation of a proton into La0.9Sr0.1(Yb 1 - XMx)O3 - δ (M = Y, In), Solid State Ionics, 10.1016/j.ssi.2013.11.044, 262, 865-869, 2014.09, 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..
17. Oda Hiroyuki, Takehiro Yoneda, Yuji Okuyama, Hiroshige Matsumoto, Preparation of nano-structured cathode for protonic ceramic fuel cell by bead-milling method, Solid State Ionics, 10.1016/j.ssi.2013.12.020, 262, 388-391, 2014.09, 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..
18. Hiroyuki Oda, Yuji Okuyama, Takaaki Sakai, Hiroshige Matsumoto, Preparation of Nano-structured La0.6Sr0.4Co 0.2Fe0.8O3-∞ cathode for protonic ceramic fuel cell by bead-milling method, Materials Transactions, 10.2320/matertrans.M2013426, 55, 4, 722-727, 2014.04, 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..
19. Yuji Okuyama, Takeshi Kozai, Shokei Ikeda, Maki Matsuoka, Takaaki Sakai, Hiroshige Matsumoto, Incorporation and conduction of proton in Sr-doped LaMO3 (M=Al, Sc, In, Yb, Y), Electrochimica Acta, 10.1016/j.electacta.2014.01.113, 125, 443-449, Volume 125, pp.443-449, 2014.04, 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..
20. Takaaki Sakai, Kaori Isa, Maki Matsuoka, Takeshi Kozai, Yuji Okuyama, Tasumi Ishihara, Hiroshige Matsumoto, Electrochemical hydrogen pumps using Ba doped LaYbO3 type proton conducting electrolyte, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2013.03.05, 38, 16, 6842-6847, 2013.05, 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..
21. Yuji Okuyama, Takeshi Kozai, Takaaki Sakai, Maki Matsuoka, Hiroshige Matsumoto, Proton transport properties of La0.9M0.1YbO 3-δ (M = Ba, Sr, Ca, Mg), Electrochimica Acta, 10.1016/j.electacta.2013.01.156, 95, 54-59, 2013.04, 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..
22. Hiroshige Matsumoto, Takaaki Sakai, Yuji Okuyama, Proton-conducting oxide and applications to hydrogen energy devices, Pure and Applied Chemistry, 10.1351/PAC-CON-12-07-11, 85, 2, 427-435, 2013.02, 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..
23. SeokJun Kim, Takaaki Sakai, Hiroyuki Oda, Yuji Okuyama, Yumi Mizutani, Junichi Hamagami, Maki matsuoka, Tasumi Ishihara, Hiroshige Matsumoto, Long-term stability of sulfated hydrous titania-based electrolyte for water electrolysis, Journal of Solid State Electrochemistry, 10.1007/s10008-012-1793-5, 16, 11, 3587-3592, 2012.11, 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..
24. Tatsumi Ishihara, Shotaro Matsushita, Takaaki Sakai, Hiroshige Matsumoto, Intermediate temperature solid oxide electrolysis cell using LaGaO 3-base oxide, Solid State Ionics, 10.1016/j.ssi.2012.02.052, 225, 77-80, 2012.10, 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..
25. Takaaki Sakai, Shotaro Matsushita, Junji Hyodo, Yuji Okuyama, Maki Matsuka, Tatsumi Ishihara, Hiroshige Matsumoto, Effect of doped ceria interlayer on cathode performance of the electrochemical cell using proton conducting oxide, Electrochimica Acta, 10.1016/j.electacta.2012.04.102, 75, 179-184, 2012.07, 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..
26. Takaaki Sakai, SeokJun Kim, Satoshi Kajitani, Junichi Hamagami, Hiroyuki Oda, Maki Matsuka, Tatsumi Ishihara, Hiroshige Matsumoto, Proton conduction properities of nano-titania modified by sulfuric acid impregnation, Journal of Solid State Electrochemistry, 10.1007/s10008-011-1616-0, 16, 6, 2055-2059, 2012.06, 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..
27. Seok-Jun Kim, Takaaki Sakai, Hiroyuki Oda, Junichi Hamagami, Yuji Okuyama, Maki Matsuka, Shinichi Ohta, Youichi Shimizu, Tatsumi Ishihara, Hiroshige Matsumoto, Water electrolysis using water-absorbing porous electrolyte consisting of a sulfonated nanotitania proton conductor, Electrochemistry, 10.5796/electrochemistry.80.246, 80, 4, 246-248, 2012.04, 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..
28. Takaaki Sakai, Junji Hyodo, Tatsumi Ishihara, Hiroshige Matsumoto, Single-nanosize pulverization of solid oxide by means of a wet planetary-bead-milling, Journal of the Ceramic Society of Japan, 120, 1397, 39-42, 2012.01, 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..
29. Keiji Yashiro, Satoshi Akoshima, Takao Kudo, Masatsugu Oishi, Hiroshige Matsumoto, Kazuhisa Sato, Tatsuya Kawada, Junichiro Mizusaki, Electrical conductivity and chemical diffusion in Perovskite-type proton conductions in H2-H2O gas mixtures, Solid State Ionics, 10.1016/j.ssi.2010.03.011, 192, 1, 76-82, 2011.06, 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..
30. Nuansaeng Sirikanda, Hiroshige Matsumoto, Tatsumi Ishihara, Effect of Co doping on oxygen permeation in Sr3Ti2O7 with Ruddlesden-Popper structure, Solid State Ionics, 10.1016/j.ssi.2010.04.018, 192, 1, 599-601, 2011.06, 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..
31. Matsumoto Hiroshige, Tanji Takayoshi, Amezawa Koji, Kawada Tatsuya, Uchimoto Yoshiharu, Furuya Yoshihisa, Sakai Takaaki, Matsuka Maki, Ishihara Tatsumi, Nanoprotonics in perovsikte-type oxides: Reversible changes in color and ion conductivity due to nanoionics phenomenon in platinum-containing perovskite oxide, Solid State Ionics, 10.1016/j.ssi.2010.11.016, 182, 1, 13-18, 2011.02, The ion conductivity of a solid-state material is primarily a function of its chemical composition and crystal structure. However, interfaces can play an important role in the conduction process. The effects of interfaces on ionic properties can be controlled on the basis of "nanoionics". In this study, we demonstrate a nanoionics phenomenon observed in a blue platinum-containing perovskite. The proton conductivity changed reversibly in response to the precipitation of platinum nanoparticles and oxidation to form a solid solution. The results of XAFS measurements, TEM analysis, and electron holography provide evidence of the nanoionics phenomenon, and suggest a possible underlying mechanism for the conductivity change caused by the small amount of precipitated platinum nanoparticles in the perovskite oxide. © 2010 Elsevier B.V..
32. Atsushi Unemoto, Atsushi Kaimai, Kazuhisa Sato, Naoto Kitamura, Keiji Yashiro, Hiroshige Matsumoto, Junichiro Mizusaki, Koji Amezawa, Tatsuya Kawada, High-Temperature Protonic Conduction in LaFeO3-SrFeO3-δ-SrZrO3 Solid Solutions, Journal of the Electrochemical Society, vol. 158, pp. B180-B188, 2011.02.
33. Takaaki Sakai, Satoshi Kajitani, Seok-Jun Kim, Jun-ichi Hamagami, Hiroyuki Oda, Maki Matsuka, Hiroshige Matsumoto, Proton conduction properties of hydrous sulfated nano-titania synthesized by hydrolysis of titanyl sulphate, Solid State Ionics, vol. 181, pp. 1746-1749, 2010.12.
34. Maki Matsuka, Roger D. Braddock, Hiroshige Matsumoto, Takaaki Sakai, Igor E. Agranovski, Tatsumi Ishihara, Experimental and theoretical studies of hydrogen permeation for doped strontium cerates, Solid State Ionics, vol. 181, pp. 1328-1335, 2010.09.
35. Atsushi Unemoto, Atsushi Kaimai, Kazuhisa Sato, Naoto Kitamura, Keiji Yashiro, Hiroshige Matsumoto, Junichiro Mizusaki, Koji Amezawa, Tatsuya Kawada, Electrical conduction and mass transport properties of SrZr0.99Fe0.01O3-δ, Solid State Ionics, vol. 181, pp. 868-873, 2010.07.
36. Maki Matsuka, Takaaki Sakai, Hiroshige Matsumoto, Roger D. Braddock, Igor E. Agranovski, Tatsumi Ishihara, Effects of hydrogen on phase stability of ytterbium doped strontium cerates, Materials Letters, vol. 64, pp. 833-835, 2010.04.
37. Sirikanda Nuansaeng, Hiroshige Matsumoto, Tatsumi Ishihara, Effects of rock-salt layer on electronic and oxide ionic mixed conductivity in strontium titanate, SrO(SrTiO3)n (n = 1, 2, ∞), Solid State Ionics, Vol. 181, pp. 315-321, 2010.03.
38. Hidehisa Hagiwara, Hiroshige Matsumoto, Tatsumi Ishihara, Dye Mixing Effects on Photocatalytic Water Splitting Activity on Dye-Modified KTaO3 Catalyst, Journal of Solar Energy Engineering-Transactions of the Asme, vol. 132, pp. 0212011-0212015, 2010.03.
39. Hao Zhong, Tatsumi Ishihara, Hiroshige Matsumoto, Ni-Fe-LaGaO3 based Alloy Anode Cermet for Direct Hydrocarbon type Solid Oxide Fuel Cell using LaGaO3 Electrolyte, Thermec 2009, vol. 638-642, pp. 1112-1117, 2010.(conference paper), 2010.01.
40. Kazuya Goto, Hiroshige Matsumoto, Tatsumi Ishihara, , Direct decomposition of NO on Ba/Ba-Y-O catalyst, Topics in Catalysis, Vol. 52, pp. 1776-1780, 2009.12.
41. Takaaki Sakai,Hiroshige Matsumoto, Reiri Yamamoto, Takao Kudo, Sachio Okada, M. Watanabe,Shinichi Hashimoto, Hitoshi Takamura, Tatsumi Ishihara, Performance of palladium electrode for electrochemical hydrogen pump using strontium-zirconate-based proton conductors, Ionics, Vol. 15, pp. 665-670, 2009.10.
42. Hao Zhong, Hiroshige Matsumoto, Tatsumi Ishihara, Ni-Fe cermet as stable anodo for direct CH4 type SOFC, ECS Transations, vol. 25, pp. 2161-2168, 2009.10.
43. Takaaki Sakai, Hiroshige Matsumoto, Yasuhiko Sato, Junji Hyodo, Naoki Ito, Shinichi Hashimoto, Tatsumi Ishihara , High sinterability of planetary-bead-milled barium zirconate, Electrochemistry, Vol. 77, pp. 876-878, 2009.10.
44. Tatsumi Ishihara, Yuko Misumi, Hiroshige Matsumoto, Pore size control for mesoporous titanium hydroxide prepared with mixed template molecules and its fluoride ion exchange property, Microporous and Mesoporous Materials, Vol. 122, pp. 87-92, 2009.06.
45. Naoki Ito, Hiroshige Matsumoto, Yuya Kawasaki, Sachio Okada, Tatsumi Ishihara, The effect of Zn addition to La1-xSrxScO3-δ systems as a B-site dopant, Chemistry Letters, Vol. 38, pp. 582-583, 2009.06.
46. Yuya Kawasaki, Sachio Okada, Naoki Ito, Hiroshige Matsumoto, Tatsumi Ishihara, Proton conduction and chemical stability of (La0.5Sr0.5)(Mg0.5+yNb0.5-y)O3-δ, Materials Research Bulletin, Vol. 44, pp. 457-461, 2009.02.
47. Tatsumi Ishihara, Hiroyuki Eto, Hao Zhong, Hiroshige Matsumoto, Intermediate temperature solid oxide fuel cells using LaGaO3 based perovskite oxide for electrolyte, Electrochemistry, Vol. 77, pp. 115-122, 2009.02.
48. Hao Zhong, Hiroshige Matsumoto, Tatsumi Ishihara, Development of Ni-Fe based cermet anode for direct CH4 fueled intermediate temperature SOFC using LaGaO3 electrolyte, Electrochemistry, Vol. 77, pp. 155-157, 2009.02, 2009.02.
49. Tatsumi Ishihara, Nuansaeng Sirikanda, Kenichi Nakashima, Syogo Miyoshi, Hiroshige Matsumoto, Mixed oxide ion and hole conductivity in Pr2-αNi0.76-xCu0.24GaxO4+δ membrane, Journal of the Electrochemical Society, Vol. 157, pp. B141-B146, 2009.01.
50. Takaaki Sakai, Shotaro Matsushita, Hiroshige Matsumoto, Sachio Okada, ShinIchi Hashimoto, Tatsumi Ishihara, Intermediate temperature steam electrolysis using strontium zirconate-based protonic conductors, International Journal of Hydrogen Energy, Vol. 34, pp. 56-63, 2009.01.
51. Hao Zhong, Hiroshige Matsumoto, Tatsumi Ishihara, Akira Toriyama,, Ag current collector for honeycomb solid oxide fuel cells using LaGaO3-based oxide electrolyte, Journal of Power Sources, Vol. 186, pp. 238-243, 2009.01.
52. YoungWan Ju, Hiroshige Matsumoto, Tatsumi Ishihara, Toru Inagaki, Hiroyuki Eto, Preparation of LaGaO3 based oxide thin film on porous ni-fe metal substrate and its SOFC Application, Journal of the Korean Ceramic Society, Vol. 45, pp. 796-801, 2008.12.
53. Atsushi Unemoto, Atsushi Kaimai, Kazuhisa Sato, Keiji Yashiro, Hiroshige Matsumoto, Junichiro Mizusaki, Koji Amezawa, Tatsuya Kawada, Hydrogen permeability and electrical properties in oxide composites, Solid State Ionics, Vol. 178, pp.1663-1667, 2008.12.
54. Naoki Ito, Satoshi Aoyama, Takatoshi Masui, Shinichi Matsumoto, Hiroshige Matsumoto, Tatsumi Ishihara, Electrochemical analysis of hydrogen membrane fuel cells, Journal of Power Sources, Vol. 185, pp. 922-926, 2008.12.
55. Takaaki Sakai, Hiroshige Matsumoto, Takao Kudo, Reiri Yamamoto, Eiki Niwa, Sachio Okada, ShinIchi Hashimoto, Kazuya Sasaki, Tatsumi Ishihara, High performance of electroless-plated platinum electrode for electrochemical hydrogen pumps using strontium-zirconate-based proton conductors, Electrochimica Acta, Vol. 53, pp. 8172-8177, 2008.11.
56. Zhonghe Bi, Hiroshige Matsumoto, and Tatsumi Ishihara, Solid-state amperometric CH4 sensor using LaGaO3-based electrolyte, Solid State Ionics, Vol. 179, pp. 1641-1644, 2008.09.
57. Hao Zhong, Hiroshige Matsumoto, Tatsumi Ishihara, Akira Toriyama,, Self-supported LaGaO3-based honeycomb-type solid oxide fuel cell with high volumetric power density, Solid State Ionics, Vol. 179, pp. 1474-1477, 2008.09.
58. Hiroshige Matsumoto, Ikuyo Nomura, Sachio Okada, Tatsumi Ishihara, Intermediate-temperature solid oxide fuel cells using perovskite-type oxide based on barium cerate, Solid State Ionics, Vol. 179, pp. 1486-1489, 2008.09.
59. Hideharu Iwakuni, Yusuke Shinmyou, Hiroaki Yano, Kazuya Goto, Hiroshige Matsumoto, Tatsumi Ishihara, Effects of added CO2 and H2 on the direct decomposition of NO over BaMnO3-based perovskite oxide, Bulletin of the Chemical Society of Japan, Volume 81, Issue 9, 2008, Pages 1175-1182, 2008.09, 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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60. Tatsumi Ishihara, Kenichi Nakashima, Sachio Okada, Makiko Enoki, Hiroshige Matsumoto, Defect chemistry and oxygen permeation property of Pr2Ni0.75Cu0.25O4 oxide doped with Ga, Solid State Ionics, Vol. 179, pp.1367-1371, 2008.09.
61. Takao Kudo, Keiji Yashiro, Hiroshige Matsumoto, Kazuhisa Sato, Tatsuya Kawada, Junichiro Mizusaki, Slow relaxation kinetics of Sr(Zr,Y)O3 in wet atmosphere, Journal of the Electrochemical Society, Vol. 155, pp. B969-B971, 2008.08.
62. Hiroyuki Michishita, Yuko Misumi, Daizo Haruta, Tatsuo Masaki,Nagaaki Yamamoto, Hiroshige Matsumoto, Tatsumi Ishihara, Cathodic performance of La0.6Sr0.4CoO3 perovskite oxide for platinum-free alkaline water electrolysis cell, Journal of the Electrochemical Society, Vol. 155, pp. B969-B971, 2008.08.
63. Tatsumi Ishihara, Jingwang Yan, Makiko Enoki, Sachio Okada, Hiroshige Matsumoto, NiFe Alloy-Supported Intermediate Temperature SOFCs Using LaGaO3 Electrolyte Film for Quick Startup, Journal of fuel cell science and technology, Vol.5, 031205-1‐031205-3, 2008.07.
64. Yohei Nomura, Tatsumi Ishihara, Yukio Hata, Kotaro Kitawaki, Kenji Kaneko, Hiroshige Matsumoto, Nanocolloidal Pd-Au as catalyst for the direct synthesis of hydrogen peroxide from H2 and O2, ChemSusChem, Vol. 1, pp. 619-621, 2008.07.
65. Naoki Ito, Hiroshige Matsumoto, Yuya Kawasaki, Sachio Okada, Tatsumi Ishihara, Introduction of In or Ga as second dopant to BaZr0.9Y0.1O3-δ to achieve better sinterability. Solid State Ionics, Solid State Ionics, Vol. 179, pp.324-329, 2008.05.
66. Yuji Yokoyama, Nobuaki Shimosaka, Hiroshige Matsumoto, Masaki Yoshio, and Tatsumi Ishihara, Effects of Supporting Electrolyte on the Storage Capacity of Hybrid Capacitors Using Graphitic and Activated Carbon, Electrochemical and Solid-State Letters, Vol.11, No.5, pp.A72pp.A75, 2008.05.
67. Hiroyuki Michishita, Hiroshige Matsumoto, Tatsumi Ishihara, Effects of pressure on the performance of water electrolysis of the cell using Nafion membrane electrode, Electrochemistry, Volume 76, Issue 4, April 2008, Pages 288-292, 2008.04, 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..
68. Tatsumi Ishihara, Yusuke Shinmyo, Kazuya Goto, Noriko Nishiyama, Hideharu Iwakuni, and Hiroshige Matsumoto, NO Decomposition on Ruddlesden‐Popper-Type Oxide,Sr3Fe2O7,Doped with Ba and Zr, Chemistry Letters, Vol.37 No.3 pp318-pp319, 2008.03.
69. Hidehisa Hagiwara, Hiroshige Matsumoto, and Tatsumi Ishihara, Improvement of Photocatalytic Activity of Metal Sulfide by Organic Dye for H2 Formation from Water, Electrochemistry, Vol.76 No.2 pp125-pp127, 2008.02.
70. Hisataka Maruyama, Hiroshige Matsumoto, Toshio Fukuda, Fumihito Arai, Functionalized hydrogel surface patterned in a chip for local PH sensing , 21st IEEE International Conference on Micro Electro Mechanical Systems, MEMS 2008 Tucson; Tucson, AZ; United States; 13 January 2008 through 17 January 2008; Category number08CH37962; Code 73225, 2008, Article number 4443633, Pages 224-227, 2008.01, 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..
71. Hideharu Iwakuni, Yusuke Shinmyou, Hiroshige Matsumoto, and Tatsumi Ishihara, Direct Decomposition of NO into N2 and O2 on SrFe0.7Mg0.3O3 Perovskite Oxides, The Chemical Society of Japan, Vol80 No.10 2007 pp.2039-2046, 2007.10.
72. Yan Jingwang, Makiko Enoki, Hiroshige Matsumoto, Tatsumi Ishihara, Nanoporous Ni-Fe bimetallic plates for nonfragile, reliable SOFCs, Electrochemical and Solid-State Letters, Volume 10, Issue 9, 2007, Pages 139-141, 2007.09, 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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73. HIROSHIGE MATSUMOTO, Yoshihisa Furuya, Sachio Okada, Takayoshi Tanji, Tatsumi Ishihara, Nanoionics phenomenon in proton-conducting oxide: Effect of dispersion of nanosize platinum particles on electrical conduction properties, Science and Technology of Advanced Materials, Volume 8, Issue 6, September 2007, Pages 531-535, 2007.09, 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..
74. Tatsumi Ishihara, Yuiko Hata, Yohei Nomura, Kenji Kaneko, and Hiroshige Matsumoto, PdAu Bimetal Supported on RutileTiO2 for Selective Synthesis of Hydrogen Peroxide by Oxidation of H2 with O2 under Atmospheric Pressure, Chemistry Letters, Vol. 36 , No. 7 p.878-879, 2007.07.
75. Hao Zhong, Hiroshige Matsumoto, Tatsumi Ishihara and Akira Toriyama, Honeycomb-type Solid Oxide Fuel Cells Using La0.9Sr0.1Ga0.8Mg0.2O3 Electrolyte, Chemistry Letters, Vol.36 No. 7 p.846-847, 2007.07.
76. H. Zhon, H. Matsumoto, T. Ishihara, A. Toriyama, Power Generating Performance of Honeycomb-type Solid Oxide Fuel Cell Consisting of LaGaO3 Based
Oxide Electrolyte
, Solid Oxide Fuel Cells 10(SOFC-X)-Part1, 7(1) pp669-675, 2007.06.
77. T. Ishihara, J. W. Yan, H. Matsumoto, High Power SOFC using LaGaO3 Based Oxide Electrolyte Film Prepared on Porous Metal Substrate, Solid Oxide Fuel Cells 10(SOFC-X)-Part1, 7(1) pp435-442, 2007.06.
78. Matsumoto, H., Y. Kawasaki, N. Ito, M. Enoki, and T. Ishihara., Relation Between Electrical Conductivity and Chemical Stability of BaCeO[sub 3]-Based Proton Conductors with Different Trivalent Dopants., Electrochemical and Solid-State Letters, 10 (4), B77-B80, 2007.04.
79. Matsumoto, H., Y. Furya, S. Okada, T. Tanji, and T. Ishihara., Effect of Dispersion of Nanosize Platinum Particles on Electrical Conduction Properties of Proton-Conducting Oxide SrZr[sub 0.9]Y[sub 0.1]O[sub 3 - alpha]., Electrochemical and Solid-State Letters, 10 (3), P11-P13, 2007.04.
80. Tatsumi Ishihara, Muneki Koga, Hiroshige Matsumoto, and Masaki Yoshio, Electrochemical Intercalation of Hexafluorophosphate Anion into Various Carbons for Cathode of Dual-Carbon Rechargeable Battery, Electrochemical and Solid-State Letters, 10(3)A74-A76, 2007.03.
81. Hideharu Iwakuni, Yusuke Shinmyou, Hiroshi Yano, Hiroshige Matsumoto, Tatsumi Ishihara, Direct decomposition of NO into N2 and O2 on BaMnO3-based perovskite oxides, Applied Catalysis B : Environmental, 74,pp299-306, 2007.03.
82. Matsum oto, H., S. Okada, S. Hashimoto, K. Sasaki, R. Yamamoto, M. Enoki, and T. Ishihara., Hydrogen separation from syngas using high-temperature proton conductors., Ionics, 2007.02.
83. Shogo Miyoshi, tetsuro Furuno, Oravan Sangoanruang, Hiroshige Matsumoto, and Tatsumi Ishihara, Mixed Conductivity and Oxygen Permeability of Doped Pr2NiO4-Based Oxides, Journal of The Electrochemical Society, 154(1)B57-B62, 2007.01.
84. Nitiphong Jirathiwathanakul, Hiroshige Matsumoto, and Tatsumi Ishihara, Intermediate Temperature Steam Electrolysis Using Doped Lanthanum Gallate Solid Electrolyte (2) Effects of CeO2 Interlayer on Activity, Eco-Materials Processing and Design VIII Materials Science Forum, Vols.544-545 pp1005-1008, 2007.01.
85. Hidehisa Hagiwara, Hiroshige Matsumoto, Tatsumi Ishihara, Effects of Dye mixing on Photocatalytic Splitting of H2O into H2 and O2 on KTaO3, Eco-Materials Processing and Design VIII Materials Science Forum, Vols.544-545 pp51-54, 2007.01.
86. Hao Zhong, Hiroshige Matsumoto, Tatsumi Ishihara, Akira Toriyama, Development of Honeycomb-type Solid Oxide Fuel Cell Consisting of LaGaO3 Electrolyte, Eco-Materials Processing and Design VIII Materials Science Forum, Vols.544-545 pp969-972, 2007.01.
87. Tatsumi Ishihara, Satoko Fukui, Makiko Enoki, and Hiroshige Matsumoto, Oxide Anode Derived from Sr-Doped LaMnO3 Perovskite Oxide for SOFCS Using LaGaO3 Electrolyte, Journal of The Electrochemical Society, 153(11)A2085-A2090, 2006.11.
88. Ishihara, T., M. Nakasu, I. Yasuda, and H. Matsumoto, Preparation of Si-carbon nanotube composite by decomposition of tetramethylsilane (TMS) and its hydrogen storage property., Science and Technology of Advanced Materials, Vol. 7 (7), 667-671., 2006.07.
89. Hidehisa Hagiwara, Naoko Ono, Takanori Inoue, Hiroshige Matsumoto, and Tatsumi Ishihara, Dye-Sensitizer Effects on a Pt/Kta(Zr)O3 Catalyst for the photocatalytic Splitting of Water, Angewandte Chemie International Edition, Number 9, 1420-1422, 2006.02.
90. J.W.Yan, H.matsumoto and T.Ishihara, Development of intermediate temperature SOFC using LaGaO3 based oxide film, Energy Materials, VOL1 NO2 pp.116-120, 2006.02.
91. Tatsumi Ishihara, Junichi tabuchi, Shinji Ishikawa, Jingwang Yan, Makiko Enoki, Hiroshige Matsumoto, Recent progress in LaGaO3 based solid electrolyte for intermediate temperature SOFCs, Solid State Ionics, 177 ,1949-1953, 2006.01.
92. Jingwang Yan, Hiroshige Matsumoto, Taner Akbay, Takashi Yamada, Tatsumi Ishihara, Prepartion of LaGaO3-based perovskite oxide film by a pulsed-laser ablation method and application as a solid oxide fuel cell electrolyte, Journal of Power Sources, 157,pp.714-pp.719, 2006.01.
93. Mizusaki, J., M. Hasegawa, K. Yashiro, H. Matsumoto, and T. Kawada, Nonstoichiometry of the perovskite-type solid solution La0.9Ca0.1Cr1-yAlyO3-δ., Solid State Ionics, Vol. 177, 1925-1928., 2006.01.
94. Tatsumi Ishihara, Jingwang Yan, Masashi Shinagawa, Hiroshige Matsumoto, Ni-Fe bimetallic anode as an active anode for intermediate temperature SOFC using LaGaO3 based electrolyte film, Electrochimica Acta, 52,pp.1645-pp.1650, 2006.01.
95. Tatsumi Ishihara, Shogo Miyoshi, Tetsuro Furuno, Oravan Sanguanruang,HiroshigeMatsumoto, Mixed Conductivity and oxygen permeability of doped Pr2 NiO4-based oxide, Solid State Ionics, 177,3087-3091, 2006.01.
96. Matsumoto, H., T. Shimura, H. Iwahara, T. Higuchi, K. Yashiro, A. Kaimai, T. Kawada, and J. Mizusaki., Hydrogen separation using proton-conducting perovskites., Journal of Alloys and Compounds, Vol. 408-412, 456-462., 2006.01.
97. Makiko Enoki, Jingwang Yan, Hiroshige Matsumoto, Tatsumi Ishihara, High oxide ion conductivity in Fe and Mg doped LaGaO3 as the electrolyte of solid oxide fuel cells, Solid State Ionics, 177 , 2053-2057, 2006.01.
98. Tatsumi Ishihara, Jingwang Yan, Hiroshige Matsumoto, Extraordinary fast oxide conductivity in La1.61GeO5-δ thin film consisting of nano-size grain, Solid State Ionics, 177 , 1733-1736, 2006.01.
99. Yan Jingwang, Hiroshige Matsumoto, Tatsumi Ishihara, Erratum: Nanosize effect on the oxide ionic conductivity of lanthanum germanite thin tilms (Electrochemical Solid-State Letters (2005) 8 (A607)) , Electrochemical and Solid-State Letters, Volume 9, Issue 1, 2006, Pages L1, 2006.01.
100. Sakai, T., Y. Fujiwara, A. Kaimai, K. Yashiro, H. Matsumoto, Y. Nigara, T. Kawada, and J. Mizusaki, Emission characteristics of negative oxygen ions into vacuum from cerium oxide., Journal of Alloys and Compounds, Vol. 408-412, 1127-1131., 2006.01.
101. Shogo Miyoshi, Tetsuro Furuno, Hiroshige Matsumoto, Tatsumi Ishihara, Conductivity and oxygen permeability of a novel oxide Pr2Ni0.8-χCu0.2FeχO4and its application to partial oxidation of CH4, Solid State Ionics, 177 , 2269-2273, 2006.01.
102. Teysuo Shimura, Hiroomi Tanaka, Hiroshige Matsumoto, Toshinobu Yogo, Influence of the transition-metal doping on conductivity of a BaCeO 3-based protonic conductor , Solid State Ionics, Volume 176, Issue 39-40, December 2005, Pages 2945-2950, 2005.12, 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..
103. Tohru Higuchi, Takeyo Tsukamoto, Hiroshige Matsumoto, Tetsuo Shimura, Keiji Yashiro, Tatsuya Kawada, Junichiro Mizusaki, Shin Shik, T. Hattori, Electronic structure of proton conducting BaCe0.90Y 0.10O3-δ , Solid State Ionics, Volume 176, Issue 39-40, December 2005, Pages 2967-2970, 2005.12, 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..
104. Fumimasa Horikiri, Tomoyuki Ichikawa, Han LiQun, Atsushi Kaimai, Keiji Yashiro, Hiroshige Matsumoto, Tatsuya Kawada, Junichiro Mizusaki, Nb-doped SrTiO3-based high-temperature Schottky solar cells, Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, Volume 44, Issue 11, 9 November 2005, Pages 8023-8026, 2005.11, 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..
105. Jingwang YAN, Makiko ENOKI, Hiroshige MATSUMOTO, and Tastumi ISHIHARA, An Intermediate Temperature Solid Oxide Fuel Cell using a La(Sr)Ga(Mg)O3 Thin Film Prepared by Pulsed Laser Deposition as Electrolyte, Electrochemistry, 73, 11, 945-950, 73,No.11,pp.945-pp.950, 2005.11.
106. Tohru Higuchi, Takeyo Tsukamoto, Hiroshige Matsumoto, Tetsuo Shimura, Keiji Yashiro, Tatsuya Kawada, Junichiro Mizusaki, Shin Shik, T. Hattori, Electronic structure of protonic conductor SrZr0.90M 0.10O3 (M = Y3+, Sc3+) probed by soft-X-ray spectroscopy , 30th Symposium on Solid State Ionics in Japan; ; 1 December 2004 through 3 December 2004; Code 65691, Volume 176, Issue 31-34, October 2005, Pages 2435-2438, 2005.10, 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..
107. keiji Yashiro, Shigenori Onuma, Maya Sase, Atsushi Kaimai, Takanori Otake, Hiroshige Matsumoto, Tatsuya Kawada, Junichiro Mizusaki, Catalytic chemical potential shift on the surface of nonstoichiometric oxides under non-equilibrium gas atmosphere, 30th Symposium on Solid State Ionics in Japan; ; 1 December 2004 through 3 December 2004; Code 65691, Volume 176, Issue 31-34, October 2005, Pages 2411-2416, 2005.10, 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..
108. Takuya Murai, Keiji Yashiro, Atsushi Kaimai, Takanori Otake, Hiroshige Matsumoto, Tatsuya Kawada, Junichiro Mizusaki, Application of FT-IR for in situ investigation of high temperature electrode reactions, 30th Symposium on Solid State Ionics in Japan; ; 1 December 2004 through 3 December 2004; Code 65691, Volume 176, Issue 31-34, October 2005, Pages 2399-2403, 2005.10, 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..
109. Jingwang Yan, Hiroshige Matsumoto, and Tatsumi Ishihara, Nanosize Effect on the Oxide Ionic Conductivity of Lanthanum Germanite Thia Films, Electrochemical and Solid-State Letters, 10.1149/1.2041333, 8, 11, A607-A610, 8(11)A607-A610, 2005.08.
110. Jingwang Yan, Hiroshige Matsumoto, Makiko Enoki, and Tatsumi Ishihara, High-Power SOFC Using La0.9Sr0.1Ga0.8Mg0.2O3-d/Ce0.8Sm0.2O2-d CompositeFilm, Electrochem. Solid State Lett, 10.1149/1.1943568, 8, 8, A389-A391, 8, p.A389-391, 2005.08.
111. Tatsumi Ishihara, Makiko Enoki, Yan JingWang, Hiroshige Matsumoto, Power generating property of sofc using La(Sr)Ga(Mg,Fe)O3 electrolyte coated with LaGaO3 film , 9th International Symposium on Solid Oxide Fuel Cells, SOFC IX; Quebec; Canada; 15 May 2005 through 20 May 2005; Code 66458, Volume PV 2005-07, 2005, Pages 1117-1126, 2005.07, 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..
112. Hiroshige MATSUMOTO, Tetsuo SHIMURA, Tohru HIGUCHI, Takanori OTAKE, Yusuke SASAKI, Keiji YASHIRO, Atsushi KAIMAI, Tatsuya KAWADA, and Junichiro MIZUSAKI, Mixed Protonic-Electronic Conduction Properties of SrZr0.9-xY0.1RuxO3-a, J. Electrochem. Soc., Vol.72, pp.861-864, 2005.03.
113. Tatsumi Ishihara, Satoko Fukui, and Hiroshige matsumoto, Effects of Water Coexisting on the Cathode Activity for the Solid Oxide Fuel Cells Using LaGaO3-Based Perovskite Oxide Electrolyte, Journal of The Electrochemical Society, 10.1149/1.2032407, 152, 10, A2035-A2039, 152(10)A2035-A2039, 2005.01.
114. H. Matsumoto, T. Shimura, T. Higuchi, H. Tanaka, K. Katahira, T. Otake, T. Kudo, K. Yashiro, A. Kaimai, T. Kawada and J. Mizusaki, Protonic-Electronic Mixed Conduction and Hydrogen Permeation in BaCe0.9-xY0.1RuxO3-, Electrochemistry, 10.1149/1.1852442, 152, 3, A488-A492, Vol. 152, pp.A488-A492, 2004.12.
115. Shogo Miyoshi, Atsushi Kaimai, Hiroshige Matsumoto, Keiji Yashiro, Yutaka Nigara, Tatsuya Kawada, Junichiro Mizusaki, In situ XRD study on oxygen-excess LaMnO3 , Fourteenth International Conference on Solid State Ionics; Monterey, CA.; United States; 22 June 2003 through 27 June 2003; Code 64000, Volume 175, Issue 1-4, 30 November 2004, Pages 383-386, 2004.11, 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..
116. keiji Yashiro, Tohru Suzuki, Atsushi Kaimai, Hiroshige Matsumoto, Yutaka Nigara, Tatsuya Kawada, Junichiro Mizusaki, Sfeir Joseph, Van Herle Jan Van, Electrical properties and defect structure of niobia-doped ceria , Fourteenth International Conference on Solid State Ionics; Monterey, CA.; United States; 22 June 2003 through 27 June 2003; Code 64000, Volume 175, Issue 1-4, 30 November 2004, Pages 341-344, 2004.11, 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..
117. Sachio Okada, Atsushi Mineshige, Akira Takasaki, Masafumi Kobune, Tetsuo Yazawa, Hiroshige Matsumoto, Tetsuo Shimura, Hiroyasu Iwahara, Zempachi Ogumi, Chemical stability of SrCe0.95Yb0.05O 3-α in hydrogen atmosphere at elevated temperatures , Fourteenth International Conference on Solid State Ionics; Monterey, CA.; United States; 22 June 2003 through 27 June 2003; Code 64000, Volume 175, Issue 1-4, 30 November 2004, Pages 593-596, 2004.11, 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..
118. Shigenori Onuma, Keiji Yashiro, Shogo Miyoshi, Atsushi Kaimai, Hiroshige Matsumoto, Yutaka nigara, Tatsuya Kawada, Junichiro Mizusaki, Kenichi Kawamura, Natsuko Sakai, Harumi Yokokawa, Oxygen nonstoichiometry of the perovskite-type oxide La 1-xCaxCrO3-δ (x=0.1, 0.2, 0.3), Solid State Ionics, Volume 174, Issue 1-4, 29 October 2004, Pages 287-293, 2004.10, 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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119. Fumimasa Horikiri, Tomoyuki Ichikawa, Atsushi Kaimai, Keiji Yashiro, Hiroshige Matsumoto, Tatsuya Kawada, Junichiro Mizusaki, High temperature photovoltaic effect at the interface of ITO / Nb doped SrTiO3, 206th ECS Meeting; Honolulu, HI; United States; 3 October 2004 through 8 October 2004; Code 66465, Volume PV 2004-16, 2004, Pages 203-209, 2004.10, 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..
120. Tohru Higuchi, Hiroshige Matsumoto, Tohru Shimura, Keiji Yashiro, Junichiro Mizusaki, Shin Shik, Takeyo Tsukamoto, Electronic structure in the band-gap region of protonic conductor SrZr 0.90Y0.10O3-δ, Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, Volume 43, Issue 8 A, August 2004, Pages 5419-5420, 2004.08, 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..
121. Tatsuya Kawada, Tomoyuki Ichikawa, Han LiQun, Keiji Yashiro, Hiroshige Matsumoto, Junichiro Mizusaki, High temperature schottky barrier on n-type SrTiO3 and its sensitivity to ambient gases, Journal of Electroceramics, Volume 13, Issue 1-3, July 2004, Pages 715-719, 2004.07, 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..
122. Tatsuya Kawada, Keiji Yashiro, Tomoaki Taura, Kenichiro Takeda, Atsushi Kaimai, Hiroshige Matsumoto, Junichiro Mizusaki, Hiroo Yugami, Microscopic observation of SOFC anodes under operation with hydrocarbon fuels, Second International Conference on Fuel Cell Science, Engineering and Technology; Rochester, NY; United States; 14 June 2004 through 16 June 2004; Code 63468, 2004, Pages 53-59, 2004.06, 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..
123. Tohru Higuchi, Hiroshige Matsumoto, Tohru Shimura, Keiji Yashiro, Tatsuya Kawada, Junichiro Mizusaki, Shin Shik, Takeyo Tsukamoto, Electronic structure of protonic conductor BaCe0.90Y 0.10O3-δ Probed by soft-X-ray spectroscopy, Japanese Journal of Applied Physics, Part 2: Letters, Volume 43, Issue 6 A, 1 June 2004, Pages L731-L734, 2004.06, 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..
124. Atsushi Mineshige, Sachio Okada, Katsura Sakai, Masafumi Kobune, Satoshi Fujii, Hiroshige Matsumoto, Tetsuo Shimura, Hiroyasu Iwahara, Zempachi Ogumi, Oxygen nonstoichiometry in SrCeO3-based high-temperature protonic conductors evaluated by Raman spectroscopy , 11th Cpnference on Solid (SSPC11); Guildford; United Kingdom; 27 August 2002 through 30 August 2002; Code 61579, Volume 162-163, September 2003, Pages 41-45, 2003.09, 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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125. Hiroshige Matsumoto, Hiroyuki Hayashi, Tohru Shimura, Hiroyasu Iwahara, Toshinobu Yogo, Electrochemical hydrogen isotope sensing via the high-temperature proton conductor CaZr0.90In0.10O3-α, Solid State Ionics, Volume 161, Issue 1-2, July 2003, Pages 93-103, 2003.07, 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..
126. Hiroshige Matsumoto, Makoto Okubo, Seiji Hamajima, Koji Katahira, Hiroyasu Iwahara, Extraction and production of hydrogen using high-temperature proton conductor, Solid State Ionics, Volume 152-153, December 2002, Pages 715-720, 2002.12, 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..
127. Tetsuo Shimura, Kazumasa Esaka, Hiroshige Matsumoto, Hiroyasu Iwahara, Protonic conduction in Rh-doped AZrO3 (A=Ba, Sr and Ca), Solid State Ionics, Volume 149, Issue 3-4, 2 August 2002, Pages 237-246, 2002.08, 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..
128. Hiroshige Matsumoto, Hiroyuki Hayashi, Hiroyasu Iwahara, Electrochemical hydrogen isotope sensor based on solid electrolytes, Journal of Nuclear Science and Technology, Volume 39, Issue 4, April 2002, Pages 367-370, 2002.08, 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..
129. Hiroshige Matsumoto, Seiji Hamajima, Hiroyasu Iwahara, Electrochemical hydrogen pump using a high-temperature-type proton conductor: Improvement of pumping capacity , 10th International Conference on Solid State (SSPC10); Montpellier; France; 24 September 2000 through 28 September 2000; Code 58750, Volume 145, Issue 1-4, 1 December 2001, Pages 25-29, 2001.12, 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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130. Hiroshige Matsumoto, Daisuke Murakami, Tetsuo Shimura, Shinichi Hashimoto, Hiroyasu Iwahara, Mixed electronic-ionic conduction in Ru-doped SrTiO3 at high temperature, Journal of Electroceramics, Volume 7, Issue 2, November 2001, Pages 107-111, 2001.11, 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..
131. Hiroshige Matsumoto, Seiji Hamajima, Tamotsu Yajima, Hiroyasu Iwahara, Electrochemical Hydrogen Pump Using SrCeO3-Based Proton Conductor: Effect of Water Vapor at the Cathode on the Pumping Capacity, Journal of the Electrochemical Society, Volume 148, Issue 10, October 2001, Pages D121-D124, 2001.10, 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..
132. Koji Katahira, Hiroshige Matsumoto, Hiroyasu Iwahara, Norihiko Fukatsu, Noriaki Kurita, Teruo Ohashi, Takuya FUjita, Takeshi Nakao, Takashi Iwamoto, Self-referenced electrode for galvanic cell-type hydrogen and steam sensors, Electrochemistry, Volume 69, Issue 7, July 2001, Pages 536-541, 2001.07, 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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133. Hiroshige Matsumoto, Takao Miyake, Hiroyasu Iwahara, Chloride ion conduction in PbCl2-PbO system, Materials Research Bulletin, Volume 36, Issue 7-8, 6 May 2001, Pages 1177-1184, 2001.05, 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..
134. Koji Katahira, Hiroshige Matsumoto, Hiroyasu Iwahara, Kunihiro Koide, Takashi Iwamoto, Solid electrolyte hydrogen sensor with an electrochemically-supplied hydrogen standard, Sensors and Actuators, B: Chemical, Volume 73, Issue 2-3, 10 March 2001, Pages 130-134, 2001.03, 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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135. Hiroshige Matsumoto, Makoto Kuribayashi, Koji Katahira, Hiroyasu Iwahara, Double-cell carbon dioxide sensor based on Li-K molten carbonate with electrochemically-supplied CO2-O2 reference, Sensors and Actuators, B: Chemical, Volume 73, Issue 2-3, 10 March 2001, Pages 157-162, 2001.03, 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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136. Tetsuro Kobayashi, Katsushi Abe, Yoshio Ukyo, Hiroshige Matsumoto, Study on current efficiency of steam electrolysis using a partial protonic conductor SrZr0.9Yb0.1O3-α, Solid State Ionics, Volume 138, Issue 3-4, 1 January 2001, Pages 243-251, 2001.01, 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..
137. Kunihiko Nakashima, Hiroshige Matsumoto, Kenichi Mori, Effect of additional elements Ni and Cr on wetting characteristics of liquid Cu on zirconia ceramics, Acta Materialia, Volume 48, Issue 18-19, 1 December 2000, Pages 4677-4681, 2000.12, 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..
138. Hiroshige Matsumoto, Hiroyasu Iwahara, Hydrogen isotope cell and its application to hydrogen isotope sensing, Solid State Ionics, Volume 136-137, 2 November 2000, Pages 173-177, 2000.11, 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..
139. Hiroyasu Iwahara, Hiroshige Matsumoto, Kazutaka Takeuchi, Electrochemical dehumidification using proton conducting ceramics, Solid State Ionics, Volume 136-137, 2 November 2000, Pages 133-138, 2000.11, 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..
140. Koji Katahira, Hiroshige Matsumoto, Hiroyasu Iwahara, Kunihiro Koide, Takashi Iwamoto, Solid electrolyte steam sensor with an electrochemically supplied hydrogen standard using proton-conducting oxides, Sensors and Actuators, B: Chemical, Volume 67, Issue 1, 10 August 2000, Pages 189-193, 2000.08, 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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141. Tetsuo Shimura, Ma Guilin, Hiroshige Matsumoto, Hiroyasu Iwahara, Non-Stoichiometry and Conduction Properties of SrxCeO3-α Oxides, Electrochemistry, Volume 68, Issue 6, June 2000, Pages 439-443, 2000.06, 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..
142. Hiroshige Matsumoto, Fumihiro Asakura, Kazutaka Takeuchi, Hiroyasu Iwahara, Transient phenomena of an electrochemical hydrogen pump using a SrCeO3-based proton conductor, Solid State Ionics , Volume 129, Issue 1, April 2000, Pages 209-218, 2000.04, 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..
143. Hiroyasu Iwahara, Tetsuo Shimura, Hiroshige Matsumoto, Protonic Conduction in Oxides at Elevated Temperatures and Their Possible Applications, Electrochemistry , Volume 68, Issue 3, March 2000, Pages 154-161, 2000.03, 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..
144. Hiroshige Matsumoto, Yosuke Lida, Hiroyasu Iwahara, Current efficiency of electrochemical hydrogen pumping using a high-temperature proton conductor SrCe0.95Yb0.05O3-α, Solid State Ionics, Volume 127, Issue 3, 2 January 2000, Pages 345-349, 2000.01, 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..
145. Hiroshige Matsumoto, Kazutaka takeuchi, Hiroyasu Iwahara, Electromotive force of H2-D2 gas cell using high-temperature proton conductors, Proceedings of the 1998 9th International Conference on Solid State Protonic Conductors (SSPC-9); Bled, Slovenia; ; 17 August 1998 through 21 August 1998; Code 55881, Volume 125, Issue 1, October 1999, Pages 377-381, 1999.10, 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..
146. Ma Guilin, Hiroshige Matsumoto, Hiroyasu Iwahara, Ionic conduction and nonstoichiometry in non-doped BaxCeO3-α, Solid State Ionics, Volume 122, Issue 1-4, 1 July 1999, Pages 237-247, 1999.07, 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..
147. Hiroshige Matsumoto, Kazutaka takeuchi, Hiroyasu Iwahara, Electromotive force of hydrogen isotope cell with a high temperature proton-conducting solid electrolyte CaZr0.90In0.10O3-α, Journal of the Electrochemical Society, Volume 146, Issue 4, April 1999, Pages 1486-1491, 1999.04, 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..
148. Hiroshige Matsumoto, Takamasa Suzuki, Hiroyasu Iwahara, Automatic regulation of hydrogen partial pressure using a proton conducting ceramic based on SrCeO3, Solid State Ionics, Volume 116, Issue 1-2, 1999, Pages 99-104, 1999.02, 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..
149. Hiroshige Matsumoto, K. Yonezawa, Hiroyasu Iwahara, Li ion conduction in LiLnSiO4 (Ln = La, Nd, Sm, Eu, Gd and Dy) sinters, Solid State Ionics, Volume 113-115, 1 December 1998, Pages 79-87, 1998.12, 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..
150. Natarajan, C., Hiroshige Matsumoto, Gyoichi Nogami, Mechanism of electrodeposition of MSe(M=Cd & Zn) films from selenosulfite solution, Bulletin of Electrochemistry, Volume 13, Issue 3, March 1997, Pages 123-128, 1997.03, 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..
151. Natarajan, C., Hiroshige Matsumoto, Gyoichi Nogami, Improvement in electrochromic stability of electrodeposited nickel hydroxide thin film, Journal of the Electrochemical Society, Volume 144, Issue 1, January 1997, Pages 121-126, 1997.01, 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..
152. Hiroshige Matsumoto, Locatelli, M. R., Kunihiko Nakashima, Glaeser, Andreas M., Katsumi Mori, Wettability of Al2O3 by liquid Cu as influenced by additives and partial transient liquid-phase bonding of Al2O3, Materials Transactions, JIM, Volume 36, Issue 4, April 1995, Pages 555-564, 1995.04, 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..
153. Shogo Miyoshi, Shigenori Onuma, Atsushi Kaimai, Hiroshige Matsumoto, Keiji Yashiro, Tatsuya Kawada, Junichiro Mizusaki, Harumi Yokokawa, Chemical stability of La 1-xSr xCrO 3 in oxidizing atmospheres, Journal of Solid State Chemistry, Volume 177, Issue 11, November 2004, Pages 4112-4118, 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.
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154. Hiroyuki Oda, Takehiro Yoneda, Takaaki Sakai, Yuji Okuyama, Hiroshige Matsumoto, Preparation of nano-structured cathode for protonic ceramic fuel cell by bead-milling method, Solid State Ionics, in press.
155. Yuji Okuyama, Shohei Ikeda, Takaaki Sakai, Hiroshige Matsumoto, Incorporation of a proton into La0.9Sr0.1(Yb1 - x Mx)O3 - δ (M = Y, In), Solid State Ionics, in press.
156. Hao Zhong, Hiroshige Matsumoto, Akira Toriyama, Tatsumi Ishihara, Honeycomb-type solid oxide fuel cell using La0.9Sr0.1Ga0.8Mg0.2O3 electrolyte for high volumetric power density, Journal of the Electrochemical Society, Vol. 156: pp. B74-B79.