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

Abstract

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 H2 at 800°C. The porous anode support layer (1 mm thick) was combined with a Ni/YSZ functional layer (∼25 μm thick), a dense YSZ electrolyte (10–20 μm thick), and porous La0.8Sr0.2MnO3−x (LSM)/YSZ cathodes (∼50 μm thick) to form anode-supported button cells for electrochemical characterization. The button cells were tested from 700 °C to 800 °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 °C without compromising power densities—up to 0.6 W/cm2 on syngas and 0.35 W/cm2 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 H2 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.