Impact of Cofiring Ceria in Ni/YSZ SOFC Anodes for Operation With Syngas and n-Butane

This study explores cofiring ceria (CeO2) with NiO and 8 mol% yttria-stabilized zirconia (YSZ) to form Ni-based cermet anodes for high-temperature solid oxide fuel cells (SOFCs) operating on syngas and n-butane/steam fuel feeds. Particular attention is paid to the suppression of carbon deposit growth in Ni-based anodes with carbonaceous fuel feeds. CeO2 was cofired with NiO and YSZ to form a porous Ni cermet anode support layer after reduction in H-2 at 800 degrees C. The porous anode support layer (1 mm thick) was combined with a Ni/YSZ functional layer (similar to 25 mu m thick), a dense YSZ electrolyte (10-20 mu m thick), and porous (La08Sr0.2MnO3-x)-Sr-. (LSM)/YSZ cathodes (similar to 50 mu m thick) to form anode-supported button cells for electrochemical characterization. The button cells were tested from 700 degrees C to 800 degrees C on various fuels including syngas and n-butane/H2O mixtures at steam-to-carbon (S/C) ratios of 1.0 and 1.5. Electrochemical testing revealed that CeO2 addition provided stable performance at 800 degrees C without compromising power densities-up to 0.6 W/cm(2) on syngas and 0.35 W/cm(2) on direct butane feeds. Furthermore, the addition of CeO2 suppressed significant carbon deposition as observed for Ni/YSZ anode support layers without CeO2. Testing with syngas at different H-2 and CO partial pressures indicated that high power densities can be maintained along an anode channel for up to 50% fuel conversion. The results indicate that cofiring CeO2 in Ni/YSZ anode support layers presents a viable option for stable SOFC operation on either prereformed or internally reformed light-hydrocarbon fuel feeds. [DOI: 10.1115/1.4006823]