Fabrication and Characterization of Freeze-Cast Tubular Solid Oxide Cells

Abstract

Increasing triple phase boundaries (TPBs) and reducing gas diffusion limitation in electrodes of solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) have always been a goal for highly desirable electrochemical performance. Freeze-casting (also called ice-templating) is a promising method to produce hierarchically arranged porous ceramics with aligned and directional pores that could assist to reach such a goal. After reviewing the previous work on ceramic freeze-casting, we focused on optimizing the processes to better engineer tubular supports for SOFC as well as SOEC applications. Although the optimized process does not have too many constraints on the types of ceramic materials (except particle size and surface area), we selected the commonly used 8 mol.% yttria stabilized zirconia (8YSZ)/NiO composite material set as a starting point. Cast slurry formulations, cast temperatures, slurry feeding methods and freeze-drying conditions were studied. Microstructures of the tubular parts prepared at various conditions were examined. Finally, as an example for SOFC application, the fuel cell performance is reported.