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 °C for 5 h, indicating that the electrolyte can be adequately densified at a relatively low firing temperature (1250 °C). 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 °C. 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.