Effect of ionic conductivity of zirconia electrolytes on polarization properties of various electrodes in SOFC

Technical Report · Tue Dec 31 04:00:00 EST 1996

DOI:https://doi.org/10.2172/460189· OSTI ID:460189

Watanabe, Masahiro; Uchida, Hiroyuki; Yoshida, Manabu ^[1]

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1. Yamanashi Univ., Kofu (Japan)

Solid oxide fuel cells (SOFCs) have been intensively investigated because, in principle, their energy conversion efficiency is fairly high. Lowering the operating temperature of SOFCs from 1000{degrees}C to around 800{degrees}C is desirable for reducing serious problems such as physical and chemical degradation of the constructing materials. The object of a series of the studies is to find a clue for achieving higher electrode performances at a low operating temperature than those of the present level. Although the polarization loss at electrodes can be reduced by using mixed-conducting ceria electrolytes, or introducing the mixed-conducting (reduced zirconia or ceria) laver on the conventional zirconia electrolyte surface, no reports are available on the effect of such an ionic conductivity of electrolytes on electrode polarizations. High ionic conductivity of the electrolyte, of course, reduces the ohmic loss. However, we have found that the IR-free polarization of a platinum anode attached to zirconia electrolytes is greatly influenced by the ionic conductivity, {sigma}{sub ion}, of the electrolytes used. The higher the {sigma}{sub ion}, the higher the exchange current density, j{sub 0}, for the Pt anode in H{sub 2} at 800 {approximately} 1000{degrees}C. It was indicated that the H{sub 2} oxidation reaction rate was controlled by the supply rate of oxide ions through the Pt/zirconia interface which is proportional to the {sigma}{sub ion}. Recently, we have proposed a new concept of the catalyzed-reaction layers which realizes both high-performances of anodes and cathodes for medium-temperature operating SOFCs. We present the interesting dependence of the polarization properties of various electrodes (the SDC anodes with and without Ru microcatalysts, Pt cathode, La(Sr)MnO{sub 3} cathodes with and without Pt microcatalysts) on the {sigma}{sub ion} of various zirconia electrolytes at 800 {approximately} 1000{degrees}C.

• Research Organization: Fuel Cell Seminar Organizing Committee (United States)
• OSTI ID: 460189
• Report Number(s): CONF-961107--Absts.; ON: TI97001494
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
36 MATERIALS SCIENCE
ANODES
CATHODES
CURRENT DENSITY
EFFICIENCY
ELECTROCHEMISTRY
IONIC CONDUCTIVITY
PERFORMANCE
POLARIZATION
SCANDIUM OXIDES
SOLID ELECTROLYTE FUEL CELLS
YTTERBIUM OXIDES
YTTRIUM OXIDES
ZIRCONIUM OXIDES