La0.8Sr0.2Cr0.98V0.02O3-delta Ce0.9Gd0.1O1.95-Ni anodes for solid oxide fuel cells - Effect of microstructure and Ni content

Solid oxide fuel cells (SOFCs) were fabricated with thick Ce0.9Gd0.1O1.95 (GDC) electrolytes, composite anodes containing La0.8Sr0.2Cr0.98V0.02O3-delta (LSCV), GDC, and NiO, and Au current collector grids. SOFCs with varying anode firing temperatures, GDC contents, and NiO contents were structurally evaluated and characterized by current-voltage measurements and electrochemical impedance spectroscopy in humidified hydrogen and air. With increasing anode firing temperature, particle sizes in the porous anodes increased and the area specific resistance (R-AS) increased (power density decreased). For lower firing temperatures, e.g., 1100 degrees C, R-AS decreased sharply with increasing NiO content from 0 to 5 wt %, but showed little further decrease from 5 to 20 wt % NiO. R-AS values were generally higher for higher firing temperatures, e.g., 1400 degrees C, decreasing gradually with increasing NiO content from 0 to 20 wt %. These trends were explained by an increase in Ni particle sizes with increasing firing temperature, making the Ni catalyst less effective. The anode polarization resistance at 750 degrees C was similar to 0.8 Omega cm(2) at 450 mV cell voltage (0.1 Omega cm(2) at open circuit), for a composition of 47.5 wt % LSCV, 47.5 wt % GDC, and 5 wt % NiO. (c) 2007 The Electrochemical Society.