Language：English   Publisher：ELSEVIER SCIENCE BV  

An all solid-state electrochemical capacitor operated in the temperature range of 150-180 degreesC was fabricated with MnO2 thin film electrode and CsHSO4 proton-conductive electrolyte. The sample has a cell structure of Au/MnO2/CsHSO4/MnO2/Au. The electrochemical behavior of the capacitor was characterized by cyclic voltammetry technique. It was found that such electrochemical capacitor exhibited a typical cyclic voltammogram of electrochemical capacitors with the average capacity of 1.30 x 10(2) F g(-1) (at 180 degreesC) and showed a significant increase of the capacity by elevating the operation temperature. This result can be explained by the enhancement of proton diffusion into the MnO2 electrode. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2004.05.033

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Language：English   Publisher：ELSEVIER SCIENCE BV  

The operating properties of solid oxide fuel cells using Ni/scandia-stabilized zirconia (Ni-ScSZ) anodes under internal reforming conditions are investigated. A single-cell achieved a maximum power density of 0.64W cm(-2) at 900degreesC in 97%CH4/3%H2O mixture fuel. The cell voltage during the power generation at 0.5 A cm(-2) is stable in 97%CH4/3%H2O mixture fuel at 900degreesC for at least 150h. By contrast, degradation of anode performance and carbon deposition are found at 800 degreesC under the same conditions. These results suggest that carbon deposition is hindered more effectively at higher temperature under operation at high current density. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2003.11.086

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Language：English   Publisher：ELSEVIER SCIENCE BV  

The oxygen ion conductor yttria-stabilized zirconia (YSZ), which is usually used as the electrolyte of SOFC, operates at high temperatures of about 1000 degreesC. The recent trend in developing SOFC is to reduce the operating temperature. Proton conducting cerates may allow the intermediate temperature operation for SOFC applications. Rare-earth-doped BaCeO3 electrolytes with the perovskite structure present good protonic conductivities at moderate temperatures but rather poor chemical stability and endurance for moisture. Barium zirconate, in contrast, is a rather stable material but exhibits low protonic conductivity. We then focused on a practical protonic conductor of BaZr0.4Ce0.4In0.2O3 (BZCI) that has a relatively high durability against moisture and good protonic conductivity. However, little is known about its stability and electrochemical properties in reducing hydrogen. In this work, the electrochemical properties of BZCI as SOFC electrolytes were investigated in concentration cell and fuel cell operations. From the results of concentration cell measurements, it was revealed that BZCI has good proton conductivities in hydrogen-rich atmospheres and behaves as a protonic and oxide ionic conductor in oxygen-rich atmospheres, with some extent of electronic conductivity, which lowers its ionic transport number. Open circuit voltage (OCV) measurements in Fuel cell operations showed that OCV value of a Pt\ BZCI\ Pt cell is about 870 mV at 800 degreesC and 1020 mV at 600degreesC. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2003.11.087

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Language：English   Publisher：ELSEVIER SCIENCE BV  

The oxygen ion conductor yttria-stabilized zirconia (YSZ), which is usually used as the electrolyte of SOFC, operates at high temperatures of about 1000 degreesC. The recent trend in developing SOFC is to reduce the operating temperature. Proton conducting cerates may allow the intermediate temperature operation for SOFC applications. Rare-earth-doped BaCeO3 electrolytes with the perovskite structure present good protonic conductivities at moderate temperatures but rather poor chemical stability and endurance for moisture. Barium zirconate, in contrast, is a rather stable material but exhibits low protonic conductivity. We then focused on a practical protonic conductor of BaZr0.4Ce0.4In0.2O3 (BZCI) that has a relatively high durability against moisture and good protonic conductivity. However, little is known about its stability and electrochemical properties in reducing hydrogen. In this work, the electrochemical properties of BZCI as SOFC electrolytes were investigated in concentration cell and fuel cell operations. From the results of concentration cell measurements, it was revealed that BZCI has good proton conductivities in hydrogen-rich atmospheres and behaves as a protonic and oxide ionic conductor in oxygen-rich atmospheres, with some extent of electronic conductivity, which lowers its ionic transport number. Open circuit voltage (OCV) measurements in Fuel cell operations showed that OCV value of a Pt\ BZCI\ Pt cell is about 870 mV at 800 degreesC and 1020 mV at 600degreesC. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2003.11.087

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Language：English   Publisher：ELSEVIER SCIENCE BV  

The operating properties of solid oxide fuel cells using Ni/scandia-stabilized zirconia (Ni-ScSZ) anodes under internal reforming conditions are investigated. A single-cell achieved a maximum power density of 0.64W cm(-2) at 900degreesC in 97%CH4/3%H2O mixture fuel. The cell voltage during the power generation at 0.5 A cm(-2) is stable in 97%CH4/3%H2O mixture fuel at 900degreesC for at least 150h. By contrast, degradation of anode performance and carbon deposition are found at 800 degreesC under the same conditions. These results suggest that carbon deposition is hindered more effectively at higher temperature under operation at high current density. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2003.11.086

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Language：English   Publisher：ELSEVIER SCIENCE BV  

Since a direct alcohol fuel cell (DAFC) can be downsized and can operate at room temperature, it is expected as a power source for mobile applications. On the other hand, cost reduction is also expected, because Pt is used in the electrocatalyst. In this study, the use of base metals for Pt was investigated by combined with the 2-propanol fuel that had an advantage compared to methanol in terms of oxidability.
The various base metal catalysts were compared to the Pt catalyst as an anode electrocatalyst in the DAFC performance. The Ni catalyst showed the highest open circuit voltage (V,,c) among the base metal catalysts. The V,,c reflected the hydrogen abstraction activity of the metal species. The Ni catalyst was a match for the Pt catalyst in the V-OC. However, the Ni catalyst could not reach to the Pt catalyst in the cell performance. The relation between the catalyst and the fuel was investigated in both the Ni and the Pt catalyst. The suitable catalytic performance was observed depending on each fuel. The Ni catalyst was suitable for the 2-propanol, while the Pt catalyst was suitable for the methanol fuel. The stripping voltammetry indicated that the DAFC showed better performance as the adsorbate could be removed easily and the easiness depended on the fuel-catalyst combinations.
Considering the catalyst cost and the possibility of the improvement in the catalyst, Ni is the potential candidate for the anode catalyst by combined with the 2-propanol fuel in the DAFC for the mobile applications. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0378-7753(03)00622-0

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Language：English   Publisher：ELSEVIER SCIENCE BV  

Temperature-programmed reduction (TPR) was performed to investigate the reducibility of the NiO/YSZ composite that is related to the anode of solid oxide fuel cells (SOFCs). The TPR profiles were found to be affected by preparation method, composition and pretreatment conditions. The calcination temperature strongly affected the reduction behavior; the TPR profile of the sample calcined at 1723 K shows a high temperature reduction peak that was not found in the TPR profile of the sample calcined at 1473 K. Such a difference in the TPR profiles can be attributed to the presence of distinct states of NiO species, which are due to the difference of interactions between NiO and YSZ. Five distinct states of NiO species are shown to be present in the NiO/YSZ composite. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0926-860X(02)00634-8

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Language：English   Publisher：ELSEVIER SCIENCE BV  

A simulation model for a tubular solid oxide fuel cell (SOFC) was developed by the object-based approach to calculate the current distribution, gas concentration distribution, and temperature distribution at the steady states and transient operation states. The transient electrical and temperature response to a load change was simulated for the both cells with the diameter of 22 mm (standard cell) and the diameter of 2.4 turn (micro-tube cell). The time required to reach the new steady state as the operating voltage was changed from 0.7 to 0.5 V for the micro-tube cell was found to be 15 s, which is much shorter than that of the standard cell. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0378-7753(03)00109-5

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Language：English   Publisher：SOC CHEMICAL ENG JAPAN  

Solid oxide fuel cells (SOFCs) with high reaction activity to use the hydrocarbon fuels are promising for solving environmental pollution problems. We designed and evaluated an SOFC system operated at 800degreesC, which uses cells and heat exchangers of micro-tubes with the outer-diameter of 2.4 mm. We found that a compact SOFC system (55.8 kg, 0.064 ml) can supply a maximum power of 64 kW for driving and that the system efficiency is 3-4 times higher than an internal combustion engine (ICE) system with a power output less than 20 kW.

DOI： 10.1252/jcej.35.1290

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Language：English   Publisher：ELECTROCHEMICAL SOC INC  

The overpotential of Ni/yttria-stabilized zirconia cermet anodes used in H-2-H2O solid oxide fuel cells (SOFCs) was studied. We measured the current-density dependence of the anodic overpotential at 850 degrees C operating temperature using the inlet fuel,oases with compositions of 100% H-2, 80% H-2 + 20% H2O, and 20% H-2 + 80% Ar. It was found that the overpotential was lower under wet-anode conditions than under dry conditions. We also showed that under wet-anode conditions the overpotential gradually increased with the increase of the current density, whereas under dry anode conditions, the overpotential increased steeply with the increase of the current density up to 20 mA/cm(2) and then showed a gradual increase with the current density. We related the overpotential of H-2-H2O SOFCs to the reaction rate constants and to the operating conditions by using a reaction model and found that the surface reaction model can successfully explain the experimental results. (C) 2000 The Electrochemical Society. S0013-4651(00)02-001-2. All rights reserved.

DOI： 10.1149/1.1393488

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Presentation type：Poster presentation  

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Presentation type：Poster presentation  

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