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Nb5+-Doped SrCoO3-δ Perovskites as Potential Cathodes for Solid-Oxide Fuel Cells.

ABSTRACT: 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.

SUBMITTER: Cascos V

PROVIDER: S-EPMC5456866 | biostudies-other | 2016 Jul

REPOSITORIES: biostudies-other

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New Rhenium-Doped SrCo1-xRexO3-δ Perovskites Performing as Cathodes in Solid Oxide Fuel Cells.

Project description:In the aim to stabilize novel three-dimensional perovskite oxides based upon SrCoO3-δ, we have designed and prepared SrCo1-xRexO3-δ phases (x = 0.05 and 0.10), successfully avoiding the competitive hexagonal 2H polytypes. Their performance as cathode materials in intermediate-temperature solid oxide fuel cells (IT-SOFC) has been investigated. The characterization of these oxides included X-ray (XRD) and in situ temperature-dependent neutron powder diffraction (NPD) experiments for x = 0.10. At room temperature, SrCo1-xRexO3-δ perovskites are defined in the P4/mmm space group, which corresponds to a subtle tetragonal perovskite superstructure with unit-cell parameters a = b ≈ ao, c = 2ao (ao = 3.861 and 3.868 Å, for x = 0.05 and 0.10, respectively). The crystal structure evolves above 380 °C to a simple cubic perovskite unit cell, as observed from in-situ NPD data. The electrical conductivity gave maximum values of 43.5 S·cm-1 and 51.6 S·cm-1 for x = 0.05 and x = 0.10, respectively, at 850 °C. The area specific resistance (ASR) polarization resistance determined in symmetrical cells is as low as 0.087 Ω·cm² and 0.065 Ω·cm² for x = 0.05 and x = 0.10, respectively, at 850 °C. In single test cells these materials generated a maximum power of around 0.6 W/cm² at 850 °C with pure H₂ as a fuel, in an electrolyte-supported configuration with La0.8Sr0.2Ga0.83Mg0.17O3-δ (LSGM) as the electrolyte. Therefore, we propose the SrCo1-xRexO3-δ (x = 0.10 and 0.05) perovskite oxides as promising candidates for cathodes in IT-SOFC.

| S-EPMC5457058 | biostudies-other

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