Abstract
In addition to the good electrochemical performance criteria in solid oxide fuel cell (SOFC) applications, cathode material must match thermal expansion with other SOFC components. Thus, effects of Ag on thermal mismatch, chemical reactions, and microstructure are investigated. Ag (1 wt% to 5 wt. %) was mixed with La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF6428) and Sm-doped ceria carbonate (SDCC) composite cathode powder. LSCF6428-SDCC-Ag samples were sintered at 600 °C for 2 h. The thermal expansion coefficients (TECs), which were determined using a dilatometer, indicated relatively less TEC mismatch between LSCF-SDCC-Ag cathodes composite and SDCC electrolyte. The average TEC value obtained from 20 °C to 600 °C implied that LSCF-SDCC-A5 (5 wt. % Ag) showed better thermal matching (13.18×10−6 K−1) with SDCC electrolyte (12.84×10−6 K−1) and achieved better compatibility. The X-ray diffraction patterns indicated that the LSCF6428-SDCC-Ag peak increased with the increase in the amount of Ag. Scanning electron microscopy analysis showed that Ag was capable of maintaining the porosity that is required for cathodes (20%–40%). Results showed that Ag exhibited desirable thermal and chemical compatibility with LSCF-SDCC. Thus, LSCF6428-SDCC-Ag can be used as a composite cathode for low-temperature SOFCs.
Highlights
Fuel cells allow the direct conversion of chemically stored energy into electrical energy by means of electrochemical oxidation of various fuels
Chemical compatibility for various concentrations of Ag on sintered LSCF-Smdoped ceria carbonate (SDCC)-Ag samples was examined via XRD test with 03-065-2871 as reference pattern (Fig. 1)
The introduction of Ag into the composite LSCF6428-SDCC cathode did not affect its composite cathode structure because no secondary peaks appeared after the powder preparation process [9]
Summary
Fuel cells allow the direct conversion of chemically stored energy into electrical energy by means of electrochemical oxidation of various fuels. The cathodes for low-temperature (LT)SOFCs should possess high electrical and ionic conductivities, enhanced electrode reaction activity, long-term stability, and adequate porosity for gas transport [2]. A difference in TEC between a cathode and an electrolyte at 7×10−6 K−1 can result in a 10% chance of delamination occurring at the first 500 h of operational [4].
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