Study on Ni-ceramic cathode degradation in H2O electrolysis using a two-dimensional patterned cell

Abstract

The degradation of fuel electrodes in solid oxide electrolysis cells (SOECs) remains a major barrier to their commercialization. The complex electrode structures of conventional cells complicate the study of degradation mechanisms. To address this challenge, this study employed a simplified electrode structure by designing and fabricating a comb shaped patterned cell to examine cathode degradation in SOECs. Yttria-stabilized zirconia (YSZ) and Ce_0.9Gd_0.1O_1.95 (GDC) were used as ceramic materials, with varying pattern sizes designed to investigate their reaction characteristics. Electrochemical analysis combined with microstructural characterization revealed that Ni detachment occurred exclusively on the GDC film, contributing to increased ohmic resistance. By contrast, no significant microstructural changes were observed in Ni-YSZ systems. These differences were likely attributed to the higher oxygen vacancy concentration at the GDC interface, resulting from the oxygen nonstoichiometry of the material. Additionally, while ohmic resistance increased, polarization resistance showed comparatively minor changes, suggesting that the reaction degradation was less severe. Further analysis of the pattern size revealed that reactions in the Ni-GDC system were not restricted to the three-phase boundary but extended to the double-phase boundary, highlighting the broader reaction region in these systems.