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

Ruddlesden Popper type oxides of LnSr 3 Fe 3 O 10−δ (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−δ , it was found that PrSr 3 Fe 3 O 10−δ shows the highest activity for the cathode reaction. The prepared LnSr 3 Fe 3 O 10−δ oxides have a tetragonal crystal structure with the space group I 4/ 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−δ are reasonably compatible with those of La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 (LSGM) electrolyte. The catalytic activity as cathodes for H 2 -SOFCs depended on Ln ions. A high cathodic activity was achieved on PrSr 3 Fe 3 O 10−δ (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, PrSr 3 Fe 3 O 10−δ is highly promising as a cathode for low temperature SOFCs.