Performance of SrCo1-xIrxO3-δ (x = 0.10 and 0.15) Perovskites as potential cathode materials for Intermediate-Temperature Solid Oxide Fuel Cells (IT-SOFC)

CASCOS, VANESSA; TRONCOSO, LORETO; LARRALDE, ANA LAURA; FERNÁNDEZ-DIAZ, MARÍA TERESA; ALONSO, JOSÉ ANTONIO

ACS Applied Energy Materials

ACS

Lugar: Washington; Año: 2020 vol. 2

2574-0962

We have designed and synthesized by wet chemical techniques a family of excellent cathode materials to be used in intermediate-temperature solid-oxide fuel cells (IT- SOFCs) devices based on SrCoO3−δ oxide. We have replaced Co by a 10 and 15% of Ir4+ in SrCo1-xIrxO3-? (x = 0.10 and 0.15), eluding the unwanted hexagonal phase of SrCoO3−δ by the introduction of a highly-charged ion at the Co position. In this way, the ionic and the electronic conductivity, together with the catalytic activity for O2 reduction, were substantially improved. After identification from X-ray diffraction (XRD), an in-situ neutron powder diffraction (NPD) study enabled the structural characterization between 25 and 800 ºC, unveiling a tetragonal to cubic phase transition around 380 ºC. A significant quantity of oxygen vacancies at 800 oC was identified, also characterized by thermogravimetric analysis. The thermal expansion is virtually linear, without abrupt changes except a subtle change of slope at 380ºC concomitant with the tetragonal-to-cubic order-disorder transition. A good chemical compatibility with the LSGM electrolyte is also shown. Electrical conductivity shows metallic behavior in the 400-850 ºC region, and impedance spectroscopy measurements yield polarization resistances as low as 0.07 Ωcm2. Finally, in-situ tests of the performance on electrolyte- supported single cells gave a power density of 891 mW/cm2 at 850ºC, using pure H2 as a fuel, demonstrating that these materials perform as excellent cathodes for IT-SOFCs.