Surface Regulating of a Double-Perovskite Electrode for Protonic Ceramic Fuel Cells to Enhance Oxygen Reduction Activity and Contaminants Poisoning Tolerance

Protonic ceramic fuel cells (PCFCs) are one of the most efficient energy conversion devices. However, the performance of current PCFCs is greatly limited by the sluggish oxygen reduction reaction (ORR) kinetics and the fast degradation of the cathode due to contaminants poisoning (such as Cr species and steam). Here, a surface regulation of a double perovskite PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) cathode by a Pr0.9Fe0.7Co0.3O3 (PFC) catalyst coating to enhance the ORR activity and stability is reported. When tested in direct contact with Cr in the air with 3% H2O at 650 °C, the polarization resistance (Rp) of the PFC coated PBSCF (PFC-PBSCF) electrode increases from ≈0.39 to 0.45 Ω cm2 after 100 h operation; in contrast, the Rp of a PBSCF electrode increases from 0.63 to 0.82 Ω cm2. Further, a PCFC with the PFC-PBSCF cathode demonstrates an excellent peak power density (≈1.08 W cm–2 at 650 °C) and significantly enhanced durability (degradation rate of 0.03% h−1), much better than those of the cells with a PBSCF cathode (≈0.75 W cm–2 and degradation rate of 0.12% h−1). Raman spectroscopy and density functional theory calculations indicate that the PFC catalyst coating diminishes the formation of Cr species, such as (Ba1-xSrx)CrO4, on the cathode surface.