(La, Pr)0.8Sr0.2FeO3−δ–Sm0.2Ce0.8O2−δ composite cathode for proton-conducting solid oxide fuel cells

• Mixed rare-earth LSPF superiorly electrical conductivity has been demonstrated.
• Proton-blocking LSPF–SDC was employed as cathode for proton-conducting SOFC.
• Excellent chemical compatibility between LSPF and SDC up to 1000 °C.
• The LSPF–SDC cathode was mechanically compatible with protonic BZCY electrolyte.
• High power density reach 488 mW cm−2, low polarization resistance of 0.071 Ω cm2.

Mixed rare-earth (La, Pr)0.8Sr0.2FeO3−δ–Sm0.2Ce0.8O2−δ (LPSF–SDC) composite cathode was investigated for proton-conducting solid oxide fuel cells based on protonic BaZr0.1Ce0.7Y0.2O3−δ (BZCY) electrolyte. The powders of La0.8−xPrxSr0.2FeO3−δ (x = 0, 0.2, 0.4, 0.6), Sm0.2Ce0.8O2−δ (SDC) and BaZr0.1Ce0.7Y0.2O3−δ (BZCY) were synthesized by a citric acid-nitrates self-propagating combustion method. The XRD results indicate that La0.8−xPrxSr0.2FeO3−δ samples calcined at 950 °C exhibit perovskite structure and there are no interactions between LPSF0.2 and SDC at 1100 °C. The average thermal expansion coefficient (TEC) of LPSF0.2–SDC, BZCY and NiO-BZCY is 12.50 × 10−6 K−1, 13.51 × 10−6 K−1 and 13.47 × 10−6 K−1, respectively, which can provide good thermal compatibility between electrodes and electrolyte. An anode-supported single cell of NiO-BZCY|BZCY|LPSF0.2–SDC was successfully fabricated and operated from 700 °C to 550 °C with humidified hydrogen (∼3% H2O) as fuel and the static air as oxidant. A high maximum power density of 488 mW cm−2, an open-circuit potential of 0.95 V, and a low electrode polarization resistance of 0.071 Ω cm2 were achieved at 700 °C. Preliminary results demonstrate that LPSF0.2–SDC composite is a promising cathode material for proton-conducting solid oxide fuel cells.