Effects of cobalt and iron proportions in Pr0.4Sr0.6Co0.9-xFexNb0.1O3-δ electrode material for symmetric solid oxide fuel cells

Abstract

Abstract Pr0.4Sr0·6Co0.9-x FexNb0.1O3-δ (PSCFxN) (x = 0, 0.2, 0.4, 0.6 and 0.9) oxides are evaluated as symmetric electrode materials for solid oxide fuel cells (SOFCs). Both the thermal expansion coefficient (TEC) and conductivity decrease with the increasing of Fe amount. With the increase in Fe content, more Fe4+ species are reduced to Fe3+, generating more oxygen vacancies. It effectively promotes the oxygen incorporation kinetics, and lowers the polarization resistance (Rp). As a result, the PSCF0·6N exhibits the lowest polarization resistance of 0.028 and 0.077 Ωm2 at 900 °C in air and hydrogen, respectively, and the highest electrical conductivity of 258.90 Scm−1 at 650 °C among all the prepared PSCFxN materials. Meanwhile, with the doping of Fe, the TEC decreases near to the electrolyte TEC value. As such, the peak power densities of the electrolyte supported PSCF0.6N-based symmetric SOFCs with different electrolyte thicknesses of 500, 400 and 300 μm are 0.642, 0.713 and 0.891 Wcm−2, respectively. Meanwhile, the output voltage of the obtained PSCF0·6N/LSGM/PSCF0·6N symmetric SOFC decreases only 5% in 50 h stability test under a current density of 0.5 Acm−2. These results indicate that the PSCF0·6N material should be a promising electrode material for the symmetric SOFCs.