研究者詳細 - 長尾　征洋

論文 - 長尾　征洋

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Pt-free intermediate-temperature fuel cells

Heo, P; Shibata, H; Nagao, M; Hibino, T

SOLID STATE IONICS 179 巻 ( 27-32 ) 頁： 1446 - 1449 2008年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Solid State Ionics

Pt-free fuel cells were investigated using a proton-conducting Sn0.9In0.1P2O7 electrolyte at intermediate temperatures between 150 and 300 °C. Transition metal oxides were applied as non Pt cathode catalysts. A ZrO2/C catalyst showed the highest catalytic activity for the oxygen reduction reaction among the metal oxides tested. The catalytic activity of ZrO2/C was further improved by optimizing the heat-treatment temperature for ZrO2/C. XRD measurements revealed that the high catalytic activity was attributed to the crystal structure of tetragonal ZrO2. Finally, we evaluated performance of a Pt-free fuel cell using the ZrO2/C cathode with a Mo2C-ZrO2/C anode that shows Pt-like behavior in reducing atmospheres. Reasonable performance was achieved by operating the Pt-free fuel cell at intermediate temperatures above 200 °C. © 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2007.12.090

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Direct dimethyl ether fuel cells at intermediate temperatures

Heo, P; Nagao, M; Sano, M; Hibino, T

JOURNAL OF THE ELECTROCHEMICAL SOCIETY 155 巻 ( 1 ) 頁： B92 - B95 2008年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Electrochemical Society

Direct dimethyl ether fuel cells (DDMEFCs) were investigated using proton-conducting Sn0.9 In0.1 P2 O7 as an electrolyte at intermediate temperatures between 150 and 300°C. Fuel cell operation at intermediate temperatures allowed a PtC anode to achieve excellent CO tolerance and high catalytic activity for the anode reaction of DME. The catalytic activity of the PtC anode was further improved by the addition of Ru to Pt, especially at elevated temperatures. The anodic overpotential and anode product measurements revealed that the H2 produced by the reforming reaction of DME was electrochemically oxidized at the PtRuC anode, which proceeded in parallel with the direct oxidation reaction of DME. As a result, DDMEFCs with the PtRuC anode achieved a peak power density of 31, 52, and 78 mW cm-2 at 200, 250, and 300°C, respectively. © 2007 The Electrochemical Society.

DOI： 10.1149/1.2803509

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Proton conduction in Sn0.95Al0.05P2O7-PBI-PTFE composite membrane

Heo, P; Kajiyama, N; Kobayashi, K; Nagao, M; Sano, M; Hibino, T

ELECTROCHEMICAL AND SOLID STATE LETTERS 11 巻 ( 6 ) 頁： B91 - B95 2008年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Electrochemical and Solid-State Letters

Proton-conducting composite membranes were fabricated by blending Sn0.95 Al0.05 P2 O7 having an excess of phosphates with polybenzimidazole (PBI) and polytetrafluoroethylene (PTFE). The addition of PBI to Sn0.95 Al0.05 P2 O7 - Px Oy powder stabilized the conductivity of the composite, providing higher conductivities than those of stoichiometric Sn0.95 Al0.05 P2 O7. The addition of PTFE to Sn0.95 Al0.05 P2 O7 - Px Oy -PBI powder reduced the conductivity but increased the tensile strength. The resulting composite membrane exhibited a conductivity of 0.04 S cm-1 at 200°C and a tensile strength of 2.30 MPa. Moreover, a fuel cell made with this composite membrane yielded high power densities exceeding 200 mW cm-2 above 100°C and good durability under unhumidified conditions. © 2008 The Electrochemical Society.

DOI： 10.1149/1.2897758

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De-NOx reactor and NOx sensor using In^<3+>-doped SnP_2O_7 with PtRhBa/C electrode 査読有り

長尾征洋

Solid State Ionics 179 頁： 1655 - 1661 2008年

Pt-free intermediate-temperature fuel cells 査読有り

長尾征洋

Solid State Ionics 97 頁： 1446 - 1449 2008年

Proton conductor in Sn_ <0.95>Al_ <0.05>P_2O_7-PBI-PTFE composite membrane 査読有り

長尾征洋

Electrochemical and Solid-State Letters 11 2008年

Direct Dimethyl Ether Fuel Cells at Intermediate Temperatures 査読有り

長尾征洋

Journal of The Electrochemical Society 155 2008年

A single-chamber SOFC stack operating in engine exhaust

Yano, M; Nagaoa, M; Okamoto, K; Inoa, AT; Uchiyarna, Y; Uchiyama, N; Hibino, T

ELECTROCHEMICAL AND SOLID STATE LETTERS 11 巻 ( 3 ) 頁： B29 - B33 2008年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Electrochemical and Solid-State Letters

Heat engines emit huge amounts of exhaust which contain considerable quantities of heat and chemical energies. An increasing public awareness of global warming and oil depletion has required the development of innovative methods of recovering energy from such exhaust. A promising approach is to produce electricity from unburned fuel by using a fuel cell system. The exhaust includes cracked-light hydrocarbons, offering the possibility of applying this system to a power generator. Solid oxide fuel cells (SOFCs) can work at elevated temperatures but have poor thermal and mechanical shock resistance. In this study, we address this problem by operating the fuel cell system in a single-chamber mode, wherein no separation between fuel and oxidant gases is required. This operation provides high tolerance toward thermal cycling and breakage of the electrolyte. As a result, a twelve-cell stack exhibits stable and high performance in the exhaust from a motorcycle. © 2007 The Electrochemical Society.

DOI： 10.1149/1.2824502

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*エンジン排ガスを利用した単室形燃料電池の開発査読有り

11 巻 ( 3 ) 頁： B29-B33 2007年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

単室形燃料電池は燃料と酸素の混合ガス中で発電が可能である。そのため、エンジン排ガス中に含有する未燃焼燃料を用いての発電が可能である。さらに構造的にスタック化も有利であり、実際にエンジン直下に取り付けたところ、スタック枚数に応じて出力を得ることができた。

Selective catalytic reduction of NOx by H2 using proton conductors as catalyst supports

Tomita, A; Yoshii, T; Teranishi, S; Nagao, M; Hibino, T

JOURNAL OF CATALYSIS 247 巻 ( 2 ) 頁： 137 - 144 2007年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Catalysis

The selective catalytic reduction (SCR) of NOx by H2 was studied using proton-conducting Sn0.9In0.1P2O7 as a catalyst support at 50-350 °C. When a mixture of 800 ppm NO, 1400-8400 ppm H2, and 5% O2 in Ar was introduced to the Pt/C working electrode, NOx was reduced to N2 with N2 selectivity values > 80 %. The reaction mechanism was shown to be based on a mixed potential at the Pt/C working electrode. This mechanism was also applicable to a Sn0.9In0.1P2O7-supported Pt catalyst. H2 SCR over the Pt/Sn0.9In0.1P2O7 catalyst was characterized by a wide operating temperature window (50-350 °C) and remarkable N2 selectivity values (> 80 %). Catalyst performance could be further improved by the addition of Rh to Pt, in which NOx conversion was a maximum 1.4 times higher than that over the Pt/Sn0.9In0.1P2O7 catalyst and N2 selectivity was increased to > 89 % at all temperatures tested. © 2007 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcat.2007.02.001

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Proton Conduction in In3+-doped SnP2O7 with Various P/(Sn+In) Ratios 査読有り

Masahiro Nagao, Toshio Kamiya, Pilwon Heo, Takashi Hibino, Mitsuru Sano, Atsuko Tomita

ECS Transaction 2 巻 ( 10 ) 頁： 43 2007年

記述言語：英語

A proton conducting, 10 mol% In3+-doped SnP2O7 was characterized by TGA, TEM measurement, and electrochemical techniques. We prepared Sn0.9In0.1P2{plus minus}xO7{plus minus}x samples with various P/(Sn+In) molar ratios from 1.7 to 2.6. Sn0.9In0.1P2O7 with a stoichiometric P/(Sn+In) molar ratio of 2.0 showed a proton conductivity of about 0.19 S cm-1 at 250oC under unhumidified conditions. When the P/(Sn+In) molar ratios were over 2.0, amorphous layer composed of phosphorus compounds were observed over the surface of Sn0.9In0.1P2O7 particles. The proton conductivity slightly increased with increasing the P/(Sn+In) molar ratios from 2.0 to 2.6. It is considered that the amorphous layer enhanced the proton conductivity by surface conduction. On the other hand, the thermal stability of this amorphous layer during heating-cooling cycle was not enough high to apply to electrochemical devises. It is important to prepare Sn0.9In0.1P2O7 with the P/(Sn+In) molar ratio of 2.0 to achieve both sufficient proton conductivity and high thermal stability.

A high-performance Mo2C-ZrO2 anode catalyst for intermediate-temperature fuel cells

Heo, P; Nagao, M; Sano, M; Hibino, T

JOURNAL OF THE ELECTROCHEMICAL SOCIETY 154 巻 ( 1 ) 頁： B53 - B56 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Electrochemical Society

Anode performance of non-Pt catalysts for hydrogen oxidation was investigated in intermediate-temperature proton exchange membrane fuel cells. Molybdenum carbide (Mo2 C) showed the highest catalytic activity among the transition metal carbides tested. Furthermore, the catalytic activity of Mo2 C was significantly improved by the addition of ZrO2 to the anode. Transmission electron microscopy and X-ray diffraction measurements revealed that Mo2 C was more highly dispersed in the Mo2 C- ZrO2 C than in the Mo2 CC, suggesting that the particle growth of Mo2 C was suppressed by the addition of ZrO2. We also tested the performance of a fuel cell using Mo2 C- ZrO2 C and Sn0.9 In0.1 P2 O7 as the anode and electrolyte materials, respectively, between 150 and 300°C. At 250°C or higher, the Mo2 C- ZrO2 C anode showed a cell performance comparable to that of the PtC anode. However, cell performance was strongly dependent on the operating temperature, reflecting that the catalytic activity of Mo2 C- ZrO2 was greatly lowered by the decrease in operating temperature. Thus it was concluded that the Mo2 C- ZrO2 catalyst is a promising alternative anode material to Pt, especially at intermediate temperatures. © 2006 The Electrochemical Society.

DOI： 10.1149/1.2382268

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Intermediate-temperature proton conduction in Al3+-doped SnP2O7

Tomita, A; Kajiyama, N; Kamiya, T; Nagao, M; Hibino, T

JOURNAL OF THE ELECTROCHEMICAL SOCIETY 154 巻 ( 12 ) 頁： B1265 - B1269 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Electrochemical Society

Al3+ -doped Sn P2 O7 proton conductors were prepared by controlling the initial composition of the reactants [Sn O2, Al (OH)3, and H3 P O4]. Sn1-x Alx Py Oz with y<2 displayed conductivities approximately two orders of magnitude lower than Sn1-x Alx P2 O7, while those of Sn1-x Alx Py Oz with y>2 exhibited conductivities at a maximum of 1.99 times higher. However, because the conductivity values of Sn1-x Alx Py Oz with y>2 were not stable, the optimal value of y in Sn1-x Alx Py Oz was determined to be 2. Partial substitution of Al3+ for Sn4+ in Sn1-x Alx P2 O7 led to an increase in the conductivity up until x=0.05. As a result, the conductivity reached 0.045 S cm-1 at 100°C, 0.15 S cm-1 at 200°C, and 0.19 S cm-1 at 300°C when the x and y values were 0.05 and 2, respectively. A hydrogen concentration cell with this material demonstrated that the ionic transport number was ∼1, and a fuel cell using this material demonstrated that the dc conductivity was comparable to the ac conductivity. © 2007 The Electrochemical Society.

DOI： 10.1149/1.2789296

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Room-temperature hydrogen sensors based on an In3+-doped SnP2O7 proton conductor

Tomita, A; Namekata, Y; Nagao, M; Hibino, T

JOURNAL OF THE ELECTROCHEMICAL SOCIETY 154 巻 ( 5 ) 頁： J172 - J176 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Electrochemical Society

A potentiometric solid-state gas sensor was fabricated using a proton-conducting Sn0.9 In0.1 P2 O7 electrolyte with an active PtC working electrode in order to study its sensing properties for small quantities (100 ppm 3%) of H2 in air at room temperature. The sensor showed electromotive force (emf) response in the negative direction to changes in the H2 concentration. Furthermore, the emf value varied linearly with the logarithm of the H2 concentration, while it was minimally affected by the water-vapor concentration. The sensing mechanism was shown to be based on the mixed potential at the working electrode through measurements of the polarization curves of H2 and air. The Sn0.9 In0.1 P2 O7 electrolyte was also applied in two single-chamber H2 sensors, wherein PtC and carbon were used as active and inactive electrodes, respectively; these electrodes were attached on the opposite surfaces or on the same surface of the electrolyte. Both single-chamber sensors could exhibit comparable H2 sensitivities, compared to the dual-chamber sensor. © 2007 The Electrochemical Society.

DOI： 10.1149/1.2713702

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Sn0.9In0.1P2O7-based organic/inorganic composite membranes application to intermediate-temperature fuel cells

Heo, P; Nagao, M; Kamiya, T; Sano, M; Tomita, A; Hibino, T

JOURNAL OF THE ELECTROCHEMICAL SOCIETY 154 巻 ( 1 ) 頁： B63 - B67 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Electrochemical Society

An anhydrous proton conductor, 10 mol % In3+ -doped SnP2 O7 (Sn0.9 In0.1 P2 O7), was composed by 1,8-bis(triethoxysilyl)octane (TES-Oct) and 3-(trihydroxysilyl)-1-propanesulfonic acid ((THS)Pro- SO3 H) and was characterized by structural and electrochemical analysis. The composite membrane with 90 wt % Sn0.9 In0.1 P2 O7 showed high proton conductivities of 0.04 S cm-1 or more between 150 and 200°C in unhumidified air. The packing of the Sn0.9 In0.1 P2 O7 particles in the matrix was relatively uniform, with no formation of pinholes observed. Fuel cell tests verified that the open-circuit voltage was maintained at a constant value of ∼970 mV regardless of the electrolyte thickness (60-200 μm), while the Ohmic resistance was decreased to 0.24 cm2 by reducing the electrolyte thickness to 60 μm. The peak power densities achieved with unhumidified H2 and air were 109 mW cm-2 at 100°C, 149 mW cm-2 at 150°C, and 187 mW cm-2 at 200°C. Furthermore, fuel cell performance was improved by hot-pressing an intermediate layer consisting of Sn0.9 In0.1 P2 O7, PtC, TES-Oct, and (THS)Pro- SO3 H between the electrolyte and cathode. © 2006 The Electrochemical Society.

DOI： 10.1149/1.2388737

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Single-chamber SOFCs using dimethyl ether and ethanol

Yano, M; Kawai, T; Okamoto, K; Nagao, M; Sano, M; Tomita, A; Hibino, T

JOURNAL OF THE ELECTROCHEMICAL SOCIETY 154 巻 ( 8 ) 頁： B865 - B870 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Electrochemical Society

An anode-supported single-chamber solid oxide fuel cell (SC-SOFC), consisting of a Ce0.9 Gd0.1 O1.9 electrolyte, a Ni- Ce0.8 Sm0.2 O1.8 (SDC) cermet anode, and a Sm0.5 Sr0.5 Co O3 cathode, was operated in a mixture feed of dimethyl ether (DME), ethanol or butane, and air at a furnace temperature of 300°C. This SC-SOFC showed comparatively poor performance for DME and ethanol fuels when compared to the performance for butane fuel, resulting from the relatively small difference in catalytic activity for DME and ethanol oxidation between the anode and the cathode. An effective improvement was achieved by attaching Ru/SDC/Ni and CuZnAl catalyst layers for DME and ethanol, respectively, on the anode surface. As a result, peak power densities of 64 and 117 mW cm-2 were obtained for DME and ethanol, respectively. © 2007 The Electrochemical Society.

DOI： 10.1149/1.2747326

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A high-performance Mo_2C-ZrO_2 anode catalyst for intermediate-temperature fuel cells 査読有り

長尾征洋

Journal of The Electrochemical Society 154 2007年

Sn_ <0.9>In_ <0.1>P_2O_7-based organic/inorganic composite membranes application to intermediate-temperature fuel cells 査読有り

長尾征洋

Journal of The Electrochemical Society 154 2007年

A proton-conducting In3+-doped SnP2O7 electrolyte for intermediate-temperature fuel cells

Nagao, M; Takeuchi, A; Heo, P; Hibino, T; Sano, M; Tomitab, A

ELECTROCHEMICAL AND SOLID STATE LETTERS 9 巻 ( 3 ) 頁： A105 - A109 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Electrochemical and Solid-State Letters

We report proton conduction in In3+ -doped Sn P2 O7 in the temperature range from 100 to 300°C, and the performance of a H2 -air fuel cell using this material as the electrolyte. The proton conductivity of In3+ -doped Sn P2 O7 was more than 10-1 S cm-1 between 125 and 300°C, and a conductivity value of 1.95× 10-1 S cm-1 was achieved at 250°C. The resulting fuel cell exhibited a reasonable power density of 264 mW cm-2 at 250°C (electrolyte thickness=0.35 mm), together with perfect tolerance toward 10% CO and good thermal stability in unhumidified conditions. © 2006 The Electrochemical Society. All rights reserved.

DOI： 10.1149/1.2159298

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Intermediate-temperature NOx sensor based on an In3+-doped SnP2O7 proton conductor

Nagao, M; Namekata, Y; Hibino, T; Sano, M; Tomita, A

ELECTROCHEMICAL AND SOLID STATE LETTERS 9 巻 ( 6 ) 頁： H48 - H51 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Electrochemical and Solid-State Letters

A potentiometric NOx sensor using a proton-conducting Sn0.9 In0.1 P2 O7 electrolyte with a PtRhC working electrode was fabricated to study sensing properties for NO and N O2 at intermediate temperatures. The sensor showed electromotive force (emf) responses to changes in NO and N O2 concentrations. Interestingly, the emf values for both NO and N O2 increased in the positive direction with increasing gas concentration. The sensing mechanism was shown to be based on a mixed potential at the working electrode through measurements of the polarization curves of NO or N O2 and water vapor. © 2006 The Electrochemical Society.

DOI： 10.1149/1.2193073

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