A-site calcium-doped Pr1−xCaxBaCo2O5+δ double perovskites as cathodes for intermediate-temperature solid oxide fuel cells

Abstract

The LnBaCo2O5+δ (Ln = rare earth) double perovskite cathodes possess superior electrochemical performance in intermediate-temperature solid oxide fuel cells (IT-SOFCs). However, high thermal expansion coefficients (TECs) and material costs are major challenges to their widespread applications. In this paper, a novel A-site Ca doping strategy that can suppress the spin-state transition of Co3+ is proposed to reduce the TECs and material costs of Pr1−xCaxBaCo2O5+δ (x = 0.1–0.4; PCBCO). Substitution of Ca for Pr effectively reduces the TEC from 22.2 × 10−6 K−1 at x = 0.1 to 19.1 × 10−6 K−1 at x = 0.3 between 100 and 800 °C. PCBCO exhibits good chemical compatibility with the Sm0.2Ce0.8O1.9 (SDC) electrolyte. The area-specific resistances of PCBCO cathodes with x = 0.1, 0.2, and 0.3 are 0.081, 0.082, and 0.089 Ω cm2, respectively, at 700 °C on the SDC electrolyte. The maximum power densities of a single cell on a 0.3 mm-thick SDC electrolyte reach 646.5, 636.8, and 620.6 mW cm−2 at 800 °C for cathodes with x = 0.1, 0.2, and 0.3, respectively. The PCBCO double perovskites exhibit excellent chemical compatibility and electrochemical performance while reducing the TECs and material costs; thus, these double perovskites are promising cathode materials for applications in IT-SOFCs.