Structural Stability of GDC Electrolyte for Low-Temperature SOFCs Depending on Fuels

Abstract

GDC (Gd 0.1 Ce 0.9 O 1-X ) has been considered as a low-temperature SOFC electrolyte. However, ceria cannot be efficiently used with hydrogen and wet hydrocarbon fuels because its structure change (Ce +4 →Ce +3 ) causes a decline of mechanical strength under a reduction atmosphere. In this work, the structural stability test of the GDC electrolyte for low-temperature SOFCs was investigated under reduction and oxidation atmospheres depending on the fuels. Each structural stability test was examined under reduction (H 2 ) and oxidation (dry CH 4 ) atmospheres at 650 o C. Micro-cracks and pinholes were observed on the electrolyte surface and at the fracture after completing the test with hydrogen fuel, but in the case of dry methane, only small amounts of defects were found at the fracture. This study clearly confirmed from the XPS data that many more Ce +4 ions transform into Ce +3 ions under the reduction (H 2 ) atmosphere (1, 2).