Faculty Profiles - HIBINO, Takashi

Single-chamber SOFCs using dimethyl ether and ethanol Reviewed Open Access

Yano Masaya, Kawai Takanori, Okamoto Kohsuke, Nagao Masahiro, Sano Mitsuru, Tomita Atsuko, Hibino Takashi

JOURNAL OF THE ELECTROCHEMICAL SOCIETY Vol. 154 ( 8 ) page： B865 - B870 2007

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：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

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

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

JOURNAL OF THE ELECTROCHEMICAL SOCIETY Vol. 154 ( 1 ) page： B63 - B67 2007

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：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

Chemical and redox stabilities of a solid oxide fuel cell with BaCe0.8Y0.2O3-alpha functioning as an electrolyte and as an anode Reviewed

Tomita Atsuko, Tsunekawa Kiyoka, Hibino Takashi, Teranishi Shinya, Tachi Yuki, Sano Mtsuru

SOLID STATE IONICS Vol. 177 ( 33-34 ) page： 2951 - 2956 2006.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Solid State Ionics

The operation of a solid oxide fuel cell (SOFC) based on BaCe0.8Y0.2O3-α (BCY20) at 800 °C was studied without using an anode material. A porous, Ce-rich phase with a fluorite structure was formed at a depth of approximately 10 μm from the BCY20 surface by heat treatment at 1700 °C. This was due to the vaporization of BaO from the BCY20 surface. This treatment improved the cell performance and chemical stability to CO2 because the Ce-rich phase functioned as an electrically conducting and protective layer. The heat-treated BCY20 also had better chemical and redox stabilities over a Ni-Ce0.8Sm0.2O1.9 (SDC) cermet anode attached to the SDC electrolyte. The cell with the heat-treated BCY20 operated well on unhumidified methane, ethane, propane, and butane without carbon deposition, while the cell with the Ni-SDC cermet anode degraded within a few hours. Moreover, the BCY20 showed higher tolerance to 10 ppm H2S and stability over 20 times redox cycling in comparison to the Ni-SDC cermet anode. © 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2006.08.031

Chemical and redox stabilities of a solid oxide fuel cell with BaCe0.8Y0.2O3-alpha functioning as an electrolyte and as an anode Reviewed

Atsuko Tomita, Kiyoka Tsunekawa, Takashi Hibino, Shinya Teranishi, Yuki Tachi, Mitsuru Sano

Solid State Ionics Vol. 177 ( 33-34 ) page： 2951-2956 2006.11

Proton conduction in In3+-doped SnP2O7 at intermediate temperatures Reviewed Open Access

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

Journal of The Electrochemical Society Vol. 153 ( 8 ) page： A1604-A1609 2006.8

Comparative performance of anode-supported SOFCs using a thin Ce0.9Gd0.1O1.95 electrolyte with an incorporated BaCe0.8Y0.2O3– layer in hydrogen and methane Reviewed

Atsuko Tomita, Shinya Teranishi, Masahiro Nagao, Takashi Hibino, Mitsuru Sano

Journal of The Electrochemical Society Vol. 153 ( 6 ) page： A956-A960 2006.6

Intermediate-temperature NOx sensor based on an in3+-doped SnP2O7 proton conductor Reviewed Open Access

Masahiro Nagao, Yosuke Namekata, Takashi Hibino, Mitsuru Sano, Atsuko Tomita

Electrochemical and Solid-State Letters Vol. 9 ( 6 ) page： H48-H51 2006.6

Performance of an intermediate-temperature fuel cell using a proton-conducting Sn0.9In0.1P2O7 electrolyte Reviewed Open Access

Pilwon Heo, Hidetaka Shibata, Masahiro Nagao, Takashi Hibino, Mitsuru Sano

Journal of The Electrochemical Society Vol. 153 ( 5 ) page： A897-A901 2006.5

*A proton-conducting In3+-doped SnP2O7 electrolyte for intermediate-temperature fuel cells Reviewed Open Access

Masahiro Nagao, Akihiko Takeuchi, Pilwon Heo, Takashi Hibino, Mitsuru Sano, Atsuko Tomita

Electrochemical and Solid-State Letters Vol. 9 ( 3 ) page： A105-A109 2006.3

Electrochemical reduction of NOx at intermediate temperatures using a proton-conducting In3+-doped SnP2O7 electrolyte Reviewed

Masahiro Nagao, Takeshi Yoshii, Takashi Hibino, Mitsuru Sano, Atsuko Tomita

Electrochemical and Solid-State Letters Vol. 9 page： J1-J4 2006.2

A high performance Pt-free anode for intermediate-temperature fuel cells Reviewed

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

ECS Transactions Vol. 3 ( 1 ) page： 453 - 458 2006

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ECS Transactions

Proton exchange membrane fuel cells (PEMFCs) are among the most promising power sources for vehicular and residential applications because of their clean and efficient energy conversion. However, these fuel cells require expensive Pt-based electrodes, which raise the cost of fuel-cell systems considerably. Here, we propose an approach to solving this problem by combining a molybdenum carbide (Mo2C) catalyst with an In3+-doped SnP 2O7 electrolyte. The resulting fuel cell can operate in the temperature range of 150 to 300°C, providing the high catalytic activity of Mo2C for electrochemical hydrogen oxidation, which is comparable to that of a Pt anode catalyst. Another important advantage of this fuel cell is that the Mo2C anode catalyst showed perfect tolerance to 10%CO. copyright The Electrochemical Society.

DOI： 10.1149/1.2356166

Comparative performance of anode-supported SOFCs using a thin Ce0.9Gd0.1O1.95 electrolyte with an incorporated BaCe0.8Y0.2O3-alpha layer in hydrogen and methane Reviewed Open Access

Tomita A, Teranishi S, Nagao M, Hibino T, Sano M

JOURNAL OF THE ELECTROCHEMICAL SOCIETY Vol. 153 ( 6 ) page： A956 - A960 2006

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of the Electrochemical Society

Multilayered Ce0.9 Gd0.1 O1.95 Ba Ce0.8 Y0.2 O3-α Ce0.9 Gd0.1 O1.95 (GDCBCYGDC) electrolytes were prepared by tape casting on a Ni- Ce0.8 Sm0.2 O1.9 anode support. The overall electrolyte thickness ranged from 30 to 35 μm, including a 3 μm thick BCY layer. When the multilayered electrolyte cell was tested with hydrogen at the anode and air at the cathode in the temperature range of 500-700°C, it yielded open-circuit voltages (OCVs) of 846-1024 mV, which were higher than the OCVs of 753-933 mV obtained for a single-layered GDC electrolyte cell under the same conditions. The corresponding peak power densities reached 273, 731, and 1025 mW cm-2 at 500, 600, and 700°C, respectively. The multilayered electrolyte cell could also be applied to direct methane solid oxide fuel cell (SOFC) and single-chamber SOFC operating in a mixture of methane and air. These SOFCs yielded OCVs of 880-950 mV and reasonable power densities without coking. © 2006 The Electrochemical Society.

DOI： 10.1149/1.2186184

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

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

ELECTROCHEMICAL AND SOLID STATE LETTERS Vol. 9 ( 3 ) page： A105 - A109 2006

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：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

Electrochemical reduction of NOx at intermediate temperatures using a proton-conducting In3+-doped SnP2O7 electrolyte Reviewed Open Access

Nagao M, Yoshii T, Hibino T, Sano M, Tomita A

ELECTROCHEMICAL AND SOLID STATE LETTERS Vol. 9 ( 2 ) page： J1 - J4 2006

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Electrochemical and Solid-State Letters

In 3+-doped SnP 2O 7 was used as the electrolyte in an electrochemical cell for the reduction of NO between 150 and 300°C in the presence of excess O 2. NO was reduced to N 2 at a Pt/C cathode when current was applied to the cell. The electrocatalytic activity of the cathode for the reduction of NO was shown to be highest at 250°C. The addition of Ba species (an oxide/carbonate mixture) to the cathode further promoted the reduction of NO by adsorbing NO more selectively than O 2 on the surface. A resulting current efficiency of 5.81% was achieved in a 2% O 2 atmosphere. © 2005 The Electrochemical Society. All rights reserved.

DOI： 10.1149/1.2149213

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

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

ELECTROCHEMICAL AND SOLID STATE LETTERS Vol. 9 ( 6 ) page： H48 - H51 2006

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：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

Performance of an intermediate-temperature fuel cell using a proton-conducting Sn0.9In0.1P2O7 electrolyte Reviewed Open Access

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

JOURNAL OF THE ELECTROCHEMICAL SOCIETY Vol. 153 ( 5 ) page： A897 - A901 2006

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of the Electrochemical Society

Performance of a fuel cell using Sn0.9 In0.1 P2 O7 as the electrolyte was evaluated in the temperature range of 150-300°C under unhumidified conditions. The IR drop and electrode overpotential of the cell were measured separately by the current interruption method. The dc conductivity values of the electrolyte between 150 and 300°C, estimated from the IR drop, were comparable to the ac conductivity values (1.48× 10-1 -1.95× 10-1 S cm-1) of the electrolyte. The cell performance was improved by forming an intermediate layer consisting of Sn0.9 In0.1 P2 O7 and PtC catalyst powders at the interface between the electrolyte and cathode, which significantly reduced the cathode polarization. As a result, the peak power density reached 264 mW cm-2 at 250°C using the 0.35-mm -thick electrolyte. The present fuel cell also showed high stability at low relative humidities (p H2 O ≈0.0075 atm) and 10% CO concentration. © 2006 The Electrochemical Society. All rights reserved.

DOI： 10.1149/1.2183927

Proton conduction in In<sup>3+</sup>-doped SnP<inf>2</inf>O<inf>7</inf> with various P/(Sn+In) ratios Reviewed

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

ECS Transactions Vol. 2 ( 10 ) page： 43 - 49 2006

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ECS Transactions

A proton conducting, 10 mol% In3+-doped SnP2O 7 (Sn0.9In0.1 P2O7) was characterized by thermogravimetric analysis (TGA), transmission electron microscope (TEM) measurement, and electrochemical techniques. We prepared Sn0.9In0.1P2=x07±x samples with various P/(Sn+In) molar ratios from 1.7 to 2.6 through the control of the amount of phosphoric acid at the preparation process in order to examine electrochemical properties and thermal stabilities. Sn0.9In 0.1P2O7 with a stoichiometric P/(Sn+In) molar ratio of 2.0 showed a proton conductivity of about 0.19 S cm-1 at 250°C under unhumidified conditions. When the P/(Sn+In) molar ratios were over 2.0, the formation of amorphous layer composed of phosphorus compounds were observed over the surface of Sn0.9In0.1P 2O7 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. As a result, it is important to prepare Sn0.9In0.1P 2O7 with the P/(Sn+In) molar ratio of 2.0 to achieve both sufficient proton conductivity and high thermal stability. Copyright The Electrochemical Society.

DOI： 10.1149/1.2408942

Proton conduction in In3+-doped SnP2O7 at intermediate temperatures Reviewed Open Access

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

JOURNAL OF THE ELECTROCHEMICAL SOCIETY Vol. 153 ( 8 ) page： A1604 - A1609 2006

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of the Electrochemical Society

SnP2 O7 -based proton conductors were characterized by Fourier transform infrared spectroscopy (FTIR), temperature-programmed desorption (TPD), X-ray diffraction (XRD), and electrochemical techniques. Undoped SnP2 O7 showed overall conductivities greater than 10-2 S cm-1 in the temperature range of 75-300°C. The proton transport numbers of this material at 250°C under various conditions were estimated, based on the ratio of the electromotive force of the galvanic cells to the theoretical values, to be 0.97-0.99 in humidified H2 and 0.89-0.92 under fuel cell conditions. Partial substitution of In3+ for Sn4+ led to an increase in the proton conductivity (from 5.56× 10-2 to 1.95× 10-1 S cm-1 at 250°C, for example). FTIR and TPD measurements revealed that the effects of doping on the proton conductivity could be attributed to an increase in the proton concentration in the bulk Sn1-x Inx P2 O7. The deficiency of P2 O7 ions in the Sn1-x Inx P2 O7 bulk decreased the proton conductivity by several orders of magnitude, which was explained as due to a decrease in the proton mobility rather than the proton concentration. The mechanism of proton incorporation and conduction is examined and discussed in detail. © 2006 The Electrochemical Society. All rights reserved.

DOI： 10.1149/1.2210669