Cu–CeO2/YSZ electrodes for SOFCs: role of cermet meso/nanostructure in methane oxidation

Abstract

The electrode microstructure in solid oxide fuel cells plays a significant role intransport and reaction phenomena. It requires interconnected pores for gas diffusionand a percolating network for efficient charge transport. Yttria-stabilizedzirconia is a commonly used material for electrode scaffolds since it can be structuredat the meso/nanoscale for improved performance, besides its high ionicconductivity, stability, and cost-effectiveness balance. However, electrode degradationremains challenging when supplied with hydrocarbons and requires furtheroptimization. This study focuses on developing mesoporous yttria-stabilizedzirconia as a precursor for a highly porous scaffold, and its infiltration with copperand cerium solution to obtain the metal-oxide composite Cu–CeO2/YSZ. Twotypes of symmetrical cells were constructed and analyzed: thin anode cells andthick anode cells. Thin anode cells were useful for selecting the best temperaturefor heat treatment of the YSZ scaffold, considering its effect on the electrode/electrolyteinterface, grain interconnection, and infiltrated phase distribution, as wellas how these microstructural features influence electrochemical performance in amethane atmosphere. Cell processing was then optimized by switching to thickanode cells, reducing the electrode resistance by an order of magnitude. Theseresults were compared with those of an electrode scaffold fabricated from commercialYSZ, concluding that the powder mesostructure was crucial in improvingelectrode microstructure, reducing polarization resistance, and enhancingtemporal stability in a direct methane-fueled cell.