The work is focused on design and characterization of mixed ionic-electronic conducting perovskite-fluorite nanocomposite ceramics as functional cathode layers in SOFC. Nanocrystalline complex oxides with ionic conductivity (YSZ, ScCeSZ, GDC, etc) and mainly electronic conductivity (Ln1-xSrxMe11-yMe2yO3, Ln2MeO4, Ln= La, Pr; Me1,2 = Mn, Co, Ni, Cu, Fe) were supported on electrolytes  by slip casting, screen-printing, and  air brushing. The sintered functional layers were studied by HRTEM  and SEM/EDS, XRD, and XPS. Redistribution of elements between perovskite-like and electrolyte domains was revealed.  Transport properties of perovskite-like oxides and nanocomposite ceramics were characterized by impedance spectroscopy for analysis of conductivity or weight variation after changing the oxygen partial pressure in the gas phase.  Oxygen isotope heteroexchange with  18O2 and C18O2 in static as well as flow reactors (SSITKA mode) was applied to estimate the oxygen self-diffusion coefficients and the specific rate of surface reaction.  Ruddlesden-Popper type nickelates Pr2-xNiO4+z demonstrated the highest oxygen mobility due to cooperative mechanism of interstitial oxygen migration. For nanocomposites, redistribution of cations between perovskite-like and electrolyte domains generates new active surface sites for O2 molecules activation. For Ruddlesden-Popper type nickelates, substitution of Pr and Ni cations by electrolyte cations  results in decreasing oxygen mobility due to hampering oxygen migration via cooperative non-linear routes.   For optimized combinations of perovskite-electrolyte, the interfaces were shown to be paths for fast oxygen diffusion with oxygen diffusion coefficients exceeding those within perovskite or electrolyte domain by up to 6 orders of magnitude.  The best perovskite-fluorite combinations with highest oxygen mobility were tested in SOFCs. SOFCs with nanocomposite cathode layers on ScCeSZ electrolyte demonstrated maximum power density  of 600-800 mW/cm2 at 700 �C in wet H2/air feeds.Support by Integration Projects  SB RAS-Belarus NAS, German-Russian Project N_CATH of CLIENT Program and Russian Federal Program �Scientific and Educational Cadres of Russia�  is gratefully acknowledged.

Nanocomposite cathodes for intermediate temperature solid oxide fuel cells

246th National Meeting (2013)

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