The commercialization of proton-conducting fuel cells (PCFCs) is hindered by the limited electroactivity and durability of cathodes at intermediate temperatures ranging from 400 to 700 °C, a challenge exacerbated by an insufficient understanding of high-entropy perovskite (HEP) materials for oxygen reduction reaction (ORR) optimization. This study introduces an yttrium-doped HEP to address these limitations. A comparative analysis of Ce_0.2−xY_xBa_0.2Sr_0.2La_0.2Ca_0.2CoO_3−δ (x = 0, 0.2; designated as CBSLCC and YBSLCC) revealed that yttrium doping enhanced the ORR activity, reduced the thermal expansion coefficient (19.9 × 10⁻⁶ K⁻¹, 30–900 °C), and improved the thermomechanical compatibility with the BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3−δ electrolytes. Electrochemical testing demonstrated a peak power density equal to 586 mW cm⁻² at 700 °C, with a polarization resistance equaling 0.3 Ω cm². Yttrium-induced lattice distortion promotes proton adsorption while suppressing detrimental Co spin-state transitions. These findings advance the development of durable, high-efficiency PCFC cathodes, offering immediate applications in clean energy systems, particularly for distributed power generation.

Three types of double perovskite La1-xPrxBa0.5Sr0.5Co1.5Fe0.5O5+δ(x=1,0.3,0) are prepared using the EDTA-citrate method and identified as solid oxide fuel cell (SOFC) cathodes. The microstructures, as well as electrochemical performances of La1-xPrxBa0.5Sr0.5Co1.5Fe0.5O5+δ (LPBSCF) and La2NiO4-impregnated LPBSCF (LN-LPBSCF) cathodes, are investigated in detail. An optimum impregnation amount of LN-LPBSCF (LN loading of 0.64 mg/cm2) electrode exhibits relatively lower electrode polarization resistance (Rp) and better stable performance as compared to that of pure LPBSCF electrode in symmetrical SOFCs. The maximum power density of LN-LPBSCF single cells is 800 mW/cm2 at 800 °C and demonstrates good stability for 100 h in short-term testing.