The Study on the Electrochemical Efficiency of Yttrium-Doped High-Entropy Perovskite Cathodes for Proton-Conducting Fuel Cells

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 Ce0.2−xYxBa0.2Sr0.2La0.2Ca0.2CoO3−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 BaZr0.1Ce0.7Y0.1Yb0.1O3−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.