Ruddlesden Popper oxides of LnSr(3)Fe(3)O(10-delta) (Ln = La, Pr, Nd, Sm, Eu, and Gd) as active cathodes for low temperature solid oxide fuel cells

Abstract

Ruddlesden Popper type oxides of LnSr(3)Fe(3)O(10-delta) (Ln - La, Pr, Nd, Sm, Eu, and Gd) have been investigated as active cathodes for solid oxide fuel cells (SOFCs). Among the examined LnSr(3)Fe(3)O(10-delta), it was found that PrSr3Fe3O10-delta shows the highest activity for the cathode reaction. The prepared LnSr(3)Fe(3)O(10-delta) oxides have a tetragonal crystal structure with the space group I4/mmm. With decreasing the ionic size of Ln(3+), the unit cell volume and crystallite size decrease. The temperature and P-O2 dependences of electrical conductivities indicate the metal-like behaviour and the predominant hole conduction. The thermal expansion coefficient (TEC) values derived from the non-linear expansion curves of LnSr(3)Fe(3)O(10-delta) are reasonably compatible with those of La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) electrolyte. The catalytic activity as cathodes for H-2-SOFCs depended on Ln ions. A high cathodic activity was achieved on LnSr(3)Fe(3)O(10-delta) (PSFO10) and a maximum power density of 0.51 W cm(-2) was achieved at 1073 K when 0.3 mm thick LSGM electrolyte was used. The surface exchange coefficient, k, also confirms the high activity for the dissociation of oxygen on PSFO10. Therefore, PrSr3Fe3O10-delta is highly promising as a cathode for low temperature SOFCs