New families of Mn+-doped SrCo1-xMxO3-δ perovskites performing as cathodes in solid-oxide fuel cells

Abstract

We have investigated the effect of M = Ti and V doping on the crystal structure and on the thermal, electrical, and electrochemical properties of SrCoMO (x = 0.03 and 0.05) perovskite oxides performing as cathodes in solid oxide fuel cells (SOFC). The characterization of these materials included x-ray (XRD) and neutron powder diffraction (NPD) measurements. The introduction of Ti and V replacing Co in SrCoO leads to the stabilization of a tetragonal perovskite superstructure at room temperature with a = a, c = 2a (a≈ 3.9 Å) defined in the P4/mmm space group, containing two inequivalent Co positions. Flattened and elongated (Co,M)O octahedra alternate along the c axis sharing corners in a three-dimensional array (3C-like structure). The thermal expansion coefficients of SrCoTiO and SrCoVO have been measured between 25 and 850 °C. The electrical conductivity at the SOFCs working temperatures (650-850 °C) seems to be sufficient to yield a good performance in IT-SOFC; the polarization resistance in symmetrical cells is as low as 0.016 Ω cm at 850 °C for M = Ti. In single test cells these materials generated a maximum power of 824 mW/cm at 850 °C with pure H as a fuel. This good performance make these systems promising candidates as cathode materials in SOFC.