Electrochemical properties of nanocrystalline y2-xPr xRu2O7 pyrochlore for electrodic application in IT-SOFCS

Abstract

Nanocrystalline powders of Y2-xPrxRu 2O7 were prepared by a co-precipitation method, and tested as an electrode on ESB and GDC electrolytes by electrochemical impedance spectroscopy in the temperature range of 300-750°C. The electrode polarization was studied as a function of praseodymium concentration in the cathode material. Both systems, Y2-xPrxRu 2O7/ESB and Y2-xPrxRu 2O7/GDC, showed a similar variation of the electrode area specific resistance (ASR). Y1.5Pr0.5Ru2O 7 cathode material presented the best performance, with ASR value of 0.19 Ωcm2 on ESB and 4.23 Ωcm2 on GDC at 700°C. Furthermore, the change in ASR with the oxygen partial pressure suggested that the rate limiting step is the surface diffusion of the adsorbed oxygen at the electrode surface to the triple-phase boundary. Thus, the low value of resistivity of the Y1.5Pr0.5Ru2O 7 in contact with ESB resulted from a much lower charge transfer resistance compared to the Y2-xPrxRu2O 7/GDC system. Also a partial solid diffusion of the cations at the electrode/electrolyte interface of Y2-xPrxRu 2O7/ESB contributed to lower the interfacial polarization. This suggested that Y2-xPrxRu2O7 is a promising material for cathode application in ESB-based electrolyte for intermediate temperature solid oxide fuel cells. © 2007 Materials Research Society.