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Novel Electrode Materials for Low-Temperature Solid-Oxide Fuel Cells. Annual Progress Report for 24 September 2001 to 23 September 2002.

DE2004833841

Publication Date	2002
Personal Author	Lu, X.; Xia, C.; Rauch, W.; Liu, M.
Page Count	24
Abstract	Composite electrodes consisting of silver and bismuth vanadates exhibit remarkable catalytic activity for oxygen reduction at 500-550 C and greatly reduce the cathode-electrolyte (doped ceria) resistances of low temperature SOFCs, down to about 0.53 (Omega)cm(sup 2) at 500 C and 0.21 (Omega)cm(sup 2) at 550 C. The observed power densities of 231, 332, and 443 mWcm(sup -2) at 500, 525 and 550 C, respectively, make it possible to operate SOFCs at temperatures about 500 C. Using in situ potential dependent FTIR emission spectroscopy, we have found evidence for two, possibly three distinct di-oxygen species present on the electrode surface. We have successfully identified which surface oxygen species is present under a particular electrical or chemical condition and have been able to deduce the reaction mechanisms. This technique will be used to probe the gas-solid interactions at or near the TPB and on the surfaces of mixed-conducting electrodes in an effort to understand the molecular processes relevant to the intrinsic catalytic activity. Broad spectral features are assigned to the polarization-induced changes in the optical properties of the electrode surface layer. The ability of producing vastly different microstructures and morphologies of the very same material is critical to the fabrication of functionally graded electrodes for solid-state electrochemical devices, such as SOFCs and lithium batteries. By carefully adjusting deposition parameters of combustion CVD, we have successfully produced oxide nano-powders with the size of 30 (approx) 200 nm. Porous films with various microstructures and morphologies are also deposited on several substrates by systematic adjustment of deposition parameters. Symmetrical cells were fabricated by depositing cathode materials on both sides of GDC electrolytes.
Keywords	Solid oxide fuel cells Electrodes Cathodes Electrolytes Substrates Emission spectroscopy Fabrication Fuel cells Oxides Reaction kinetics Cost reduction Electrochemistry Vandates Silver Bismuth Anodes
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Georgia Inst. of Tech., Atlanta. School of Materials Science and Engineering.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200516

Novel Electrode Materials for Low-Temperature Solid-Oxide Fuel Cells. Annual Progress Report for 24 September 2001 to 23 September 2002.

Novel Electrode Materials for Low-Temperature Solid-Oxide Fuel Cells. Annual Progress Report for 24 September 2001 to 23 September 2002.
DE2004833841

Publication Date	2002
Personal Author	Lu, X.; Xia, C.; Rauch, W.; Liu, M.
Page Count	24
Abstract	Composite electrodes consisting of silver and bismuth vanadates exhibit remarkable catalytic activity for oxygen reduction at 500-550 C and greatly reduce the cathode-electrolyte (doped ceria) resistances of low temperature SOFCs, down to about 0.53 (Omega)cm(sup 2) at 500 C and 0.21 (Omega)cm(sup 2) at 550 C. The observed power densities of 231, 332, and 443 mWcm(sup -2) at 500, 525 and 550 C, respectively, make it possible to operate SOFCs at temperatures about 500 C. Using in situ potential dependent FTIR emission spectroscopy, we have found evidence for two, possibly three distinct di-oxygen species present on the electrode surface. We have successfully identified which surface oxygen species is present under a particular electrical or chemical condition and have been able to deduce the reaction mechanisms. This technique will be used to probe the gas-solid interactions at or near the TPB and on the surfaces of mixed-conducting electrodes in an effort to understand the molecular processes relevant to the intrinsic catalytic activity. Broad spectral features are assigned to the polarization-induced changes in the optical properties of the electrode surface layer. The ability of producing vastly different microstructures and morphologies of the very same material is critical to the fabrication of functionally graded electrodes for solid-state electrochemical devices, such as SOFCs and lithium batteries. By carefully adjusting deposition parameters of combustion CVD, we have successfully produced oxide nano-powders with the size of 30 (approx) 200 nm. Porous films with various microstructures and morphologies are also deposited on several substrates by systematic adjustment of deposition parameters. Symmetrical cells were fabricated by depositing cathode materials on both sides of GDC electrolytes.
Keywords	Solid oxide fuel cells Electrodes Cathodes Electrolytes Substrates Emission spectroscopy Fabrication Fuel cells Oxides Reaction kinetics Cost reduction Electrochemistry Vandates Silver Bismuth Anodes
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Georgia Inst. of Tech., Atlanta. School of Materials Science and Engineering.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200516