Properties of pyrochlore ruthenate cathodes for intermediate temperature solid oxide fuel cells

摘要

Powders of Bi{sub}2Ru{sub}2O{sub}7.3, Pb{sub}2Ru{sub}2O{sub}6.5, and Y{sub}2Ru{sub}2O{sub}7 were prepared and their reactivity with Ce{sub}0.9Gd{sub}0.1O{sub}1.95 (CGO) electrolyte powders examined. Bi{sub}2Ru{sub}2O{sub}7.3 and Pb{sub}2Ru{sub}2O{sub}6.5 reacted with CGO but Y{sub}2Ru{sub}2O{sub}7 appeared stable when heated in contact with CGO powder at 900C for 24 h. Symmetrical electrodes of Y{sub}2Ru{sub}2O{sub}(7-x) were deposited on CGO ceramic pellets, either by tape-casting or by electrostatic assisted chemical vapor deposition (EACVD) techniques, and cathode resistivities determined by impedance spectroscopy. Undoped Y{sub}2Ru{sub}2O{sub}7 electrodes exhibited very high area specific resistivities (ASR) at 627C ( 4000Ωcm{sup}2), but by doping with SrO the resistivity was reduced almost 100×to 47Ωcm{sup}2. The behavior of the Y{sub}2Ru{sub}2O{sub}7 cathodes was intetpreted in terms of available oxygen ion transport data for the Gd{sub}2Ti{sub}2O{sub}7 series, and it was concluded that optimization of pyrochlore ruthenate compositions should be possible to improve further the oxygen reduction behavior of ruthenate cathodes for intermediate temperature solid oxide fuel cells.