Structural stability of the GDC electrolyte for low temperature SOFCs depending on fuels

摘要

It has been considered to apply Gd_(0.1)Ce_(0.9)O _(1-x) (GDC) to low temperature solid oxide fuel cell (SOFC) electrolytes at a low temperature. 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 reducing atmosphere. In this work, the structural stability test of the GDC electrolyte was investigated under H_2 and dry CH_4 atmospheres depending on the fuels at 650°C. This study clearly confirmed from the scanning electron microscopy, X-ray photoelectron spectroscopy, and mechanical strength data that many more Ce~(4+) ions transform into Ce~(3+) ions under the reducing (H_2) atmosphere [J. Alloys Compd., 408-412, 628 (2006); Solid State Sci., 7, 539 (2005)].