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The performance of intermediate-temperature solid-oxide fuel cells (IT-SOFC) prominently depends on the catalytic properties of the cathode materials in the oxygen reduction reaction. With this in mind, SrCo 1−x Ru x O 3−δ (x = 0.00, 0.05, 0.10, and 0.15) perovskite phases have been designed and prepared combining the oxygen-diffusion features of SrCoO 3−δ oxide with the catalytic activity of Ru 4+ ions. Additionally, the presence of Ru contributes to stabilize a tetragonal perovskite. Xray diffraction (XRD) and in situ temperature-dependent neutron powder diffraction (NPD) experiments for x = 0.1 are used to characterize these materials. A tetragonal P4/mmm space group is observed at room temperature for SrCo 1−x Ru x O 3−δ perovskites. The crystal structure changes into a simple-cubic perovskite unit cell above 400 °C. This can be observed from in situ NPD data. An electrical conductivity between 130 and 60 S/cm at 850 °C was obtained. Its performance as cathode materials has been investigated in single test cells, generating an exceptional power density of 1.1 W/cm 2 at 850 °C with pure H 2 as a fuel. Therefore, SrCo 1−x Ru x O 3−δ (x = 0.05, 0.10, and 0.15) perovskite oxides seem to be auspicious IT-SOFC cathode candidates.

SrCoO3−δ outperforms as cathode material in solid-oxide fuel cells (SOFC) when the three-dimensional (3C-type) perovskite structure is stabilized by the inclusion of highly-charged transition-metal ions at the octahedral positions. In a previous work we studied the Nb incorporation at the Co positions in the SrCo1−xNbxO3−δ system, in which the stabilization of a tetragonal P4/mmm perovskite superstructure was described for the x = 0.05 composition. In the present study we extend this investigation to the x = 0.10–0.15 range, also observing the formation of the tetragonal P4/mmm structure instead of the unwanted hexagonal phase corresponding to the 2H polytype. We also investigated the effect of Nb5+ doping on the thermal, electrical, and electrochemical properties of SrCo1−xNbxO3−δ (x = 0.1 and 0.15) perovskite oxides performing as cathodes in SOFC. In comparison with the undoped hexagonal SrCoO3−δ phase, the resulting compounds present high thermal stability and an increase of the electrical conductivity. The single-cell tests for these compositions (x = 0.10 and 0.15) with La0.8Sr0.2Ga0.83Mg0.17O3−δ (LSGM) as electrolyte and SrMo0.8Fe0.2CoO3−δ as anode gave maximum power densities of 693 and 550 mW∙cm−2 at 850 °C respectively, using pure H2 as fuel and air as oxidant.