High-Entropy Perovskite Electrolyte for Protonic Ceramic Fuel Cells Operating below 600 °C

High-entropy materials are attracting ever-increasing concern for their unique structural features and unprecedented potential applications. In this study, we design and successfully prepared single-phase high-entropy perovskite oxide (HEPO) BaSn 0.16 Zr 0.24 Ce 0.35 Y 0.1 Yb 0.1 Dy 0.05 O 3−δ (BSZCYYbD) to use as a new class of proton conductor, which is first applied to protonic ceramic fuel cells (PCFCs) below 600 °C. The BSZCYYbD exhibits excellent chemical and structural stability, high densification, and mechanical properties. The protonic conduction in BSZCYYbD is proved by the proton-conductor isotope effect and hydration effect. The protonic conductivity of BSZCYYbD is the highest ever reached in the high-entropy proton conductors, which is 8.3 mS cm –1 in humidified air (3% H 2 O) at 600 °C. An anode-based PCFC with BSZCYYbD electrolyte (∼45 μm) demonstrates a favorable output of 318 mW cm –2 at 600 °C. Our study offers a strategy for the design of superior proton-conducting electrolytes based on HEPOs, which hold promise for diverse electrochemical applications.