Enhanced reducibility of ceria–YSZ composites in solid oxide electrodes

Abstract

Composites prepared by infiltration of 50- wt% ceria into porous YSZ were investigated for use as H₂–H₂O electrodes for solid oxide electrolyzers (SOE) or fuel cells (SOFC). Cells prepared from these composites showed excellent performance, with SOFC power densities as high as 1.1 W cm⁻² at 1073 K. Further investigations into the electrodes showed that they had significantly higher conductivities than would be expect for a material that was only 35 vol% ceria, as high as 0.25 S cm⁻¹ at 1073 in 3% H₂O–97% H₂ mixtures. An investigation into the thermodynamic redox properties of the composite using coulometric titration at 973 K indicated that the ceria in the composite remained significantly reduced to higher P(O₂) compared to pure ceria, probably due to interactions at the ceria–YSZ interface.