| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2000: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1999: ¥2,100,000 (Direct Cost: ¥2,100,000)
|
|---|
| Research Abstract |
Solid oxide fuel cells (SOFCs) are expected to provide the highest energy conversion efficiency among various types of fuel cells. At present, the SOFC operating temperatures are restricted to very high values of about 1000℃ because of insufficient performances of the state-of-the-art electrolyte and electrodes at low temperatures. It is desirable, however, to operate SOFCs at a medium temperature (-800℃) because high-temperature operation causes many serious problems : degradation of SOFC components, limited choice of materials, etc. Two major obstacles must be solved to operate mediunm-temperature SOFCs. The first is to reduce an ohmic loss in the solid electrolyte. Besides reducing the ohmic loss, it is essential to develop high performance electrodes because the electrode reaction rates must be slow down at such temperatures.
We have developed a porous catalyzed-reaction layer for medium-temperature SOFCs. Mixed conducting oxide particles, samaria-doped ceria [(CeO_2)_<0.8>(SmO_<1.5
… More
>)_<0.2>, denoted as SDC] for the anode and La(Sr)MnO_3 (LSM) for the cathode, were employed in combination with highly dispersed (nanometer-sized) metal electrocatalysts on their surfaces.
The aim of this research work is to contribute to development of high-performance medium-temperature SOFC by fabricating novel electrodes with high performance and high reliability.
In FY1999, we succeeded to develop new cathodes with exceptionally high-performance. La(Sr)CoO_3 (LSC) has been known to exhibit a higher cathodic performance than LSM.However, LSC tends to react easier with yttria-stabilized zirconia (YSZ) electrolyte than LSM at high temperatures. We found that a thin and dense SDC interlayer was effective to avoid unfavorable solid-state reactions between LSC and YSZ.Control of the microstructure of LSC cathode appreciably lowered the IR-free overpotential without an increase of the ohmic resistance. The cathode performance was enhanced further with highly dispersed Pt catalysts of 3 wt% loading, especially at low operating temperature. The current density on the Pt-LSC cathode at an overpotential (η) of -0.05 V was 1 A/cm^2 at 800℃ in air.
In FY2000, we succeeded to enhance the anode performance by employing yttria-doped ceria (YDC) in place of SDC.We found that the porous YDC anode exhibited higher performance than that of SDC at the operating temperature of 800℃ to 1000℃. High electronic conductivity in the mixed conducting YDC appreciably contributes to enhancing the anode reaction rate. Highly dispersed Ru catalysts (3 wt%) effectively enhanced the performance of the YDC anode. The current density of 0.4 A/cm^2 at η= 0.1 V was achieved at 800℃ in humidified H_2. In conclusion, they are promising electrodes for medium-temperature SOFCs. Less
|
