Microstructures, conductivities, and electrochemical properties of Ce0.9Gd0.1O2 and GDC-Ni anodes for low-temperature SOFCs

Powder of gadolinia-doped ceria (GDC, Gd0.1Ce0.9O1.95), prepared using a glycine-nitrate process, is used to fabricate anode-supported solid oxide fuel cells (SOFCs) by dry pressing. The microstructure, conductivity, and electrochemical properties of the GDC powder are studied as a function of sintering conditions. Results show that the relative density of the GDC electrolyte is about 92%, 95%, and 97%, respectively, when sintered at 1250, 1350, and 1450 degreesC for 5 h, indicating that the electrolyte can be adequately densified at a relatively low firing temperature (1250 degreesC). The conductivities of the electrolytes, however, are relatively insensitive to the sintering temperature. Using humidified (3% H2O) hydrogen as fuel and stationary air as oxidant, the electrochemical properties of the anodes are studied at temperatures from 400 to 600 degreesC. Impedance analysis indicates that the cathodic interfacial polarization is much larger than the anodic polarization under testing conditions. However, anodes sintered at a lower temperature exhibit better electrochemical performance than those sintered at a higher temperature. (C) 2002 Elsevier Science B.V. All rights reserved.