Chemical compatibility, redox behavior, and electrochemical performance of Nd_(1-x)Sr_xCoO_(3-δ) cathodes based on Ce_(1.9)Gd_(0.1)O_(1.95) for intermediate-temperature solid oxide fuel cells

摘要

The effect of Sr substitution for Nd on Nd_(1-x)Sr_xCoO_(3-δ) (NSC) (x = 0.3, 0.4, 0.5, 0.6, and 0.7) is investigated to evaluate NSC as a cathode material based on Gd_(0.1)Ce_(0.9)O_(1.95) (GDC) electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The NSC powders are prepared by the glycine nitrate method. At a given temperature, the electrical conductivity increases with increasing Sr content up to x = 0.5 and then decreases for x>0.5. The redox behavior of NSC (x = 0.3, 0.5, and 0.7) cathodes is studied by the coulometric titration at 700℃. In order to investigate the area specific resistances of NSC-GDC cathodes, symmetrical half cells (cathode/electrolyte/cathode) are measured using impedance spectroscopy at various temperatures in air under open circuit voltage (OCV) condition. The electrochemical performance of NSC-GDC cathodes is measured using an NSC-GDC/GDC/Ni-GDC anode supported cell. The maximum power density of NSC-GDC cathodes increases with increasing strontium content up to x = 0.5 and then decreases at 700℃. In terms of electrical conductivity and electrochemical performance, Nd_(1-x)Sr_xCoO_(3-δ) (x=0.5) is more suitable as a cathode material based on GDC electrolyte in IT-SOFC applications.