Chemical compatibility, redox behavior, and electrochemical performance of Nd1−xSrxCoO3−δ cathodes based on Ce1.9Gd0.1O1.95 for intermediate-temperature solid oxide fuel cells

Abstract

The effect of Sr substitution for Nd on Nd1−xSrxCoO3−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 Gd0.1Ce0.9O1.95 (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°C. 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°C. In terms of electrical conductivity and electrochemical performance, Nd1−xSrxCoO3−δ (x=0.5) is more suitable as a cathode material based on GDC electrolyte in IT-SOFC applications.