A-site double-lanthanide-doped La1−xPrxBaCo2O5+δ cathode materials for intermediate-temperature solid oxide fuel cells
Double-perovskite materials La 1− x Pr x BaCo 2 O 5+ δ (LPBCO), suitable for the application of intermediate-temperature solid oxide fuel cell (IT-SOFC) and other electrochemical devices, were successfully prepared through solid-state reaction method. The effects of La and Pr doping ratios on the crystallographic structure, thermochemical stability, thermal expansion, electrical conductivity, and electrochemical polarizations were analyzed and discussed. The X-ray diffraction results show that the crystal structure changes from single perovskite to double perovskite with the increase in Pr doping content. LPBCOs present excellent chemical stability with conventional electrolyte GDC at less than 1100 °C. The thermal expansion can be effectively reduced upon doping of Pr. The materials demonstrate high electrical conductivity even under relatively low temperatures, i.e., LP-73 ( x = 0.3 with single perovskite) has the highest conductivity at 1680 S/cm at 400 °C. Among the double-perovskite compositions, LP-55 presents the highest performance in electrical conductivity though. Analysis of the electrochemical impedance spectra of LPBCOs symmetric cells reveals low area specific polarization resistances for these double-lanthanide-doped double-perovskite materials, and the charge transfer is determined as the dominating sub-process for the oxygen transport through the materials. All the findings show that La 1− x Pr x BaCo 2 O 5+ δ possesses excellent oxygen reduction activity and is promising for the application in IT-SOFCs.
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