An advanced bifunctional single-element-incorporated ternary perovskite cathode for next-generation fuel cells

Bifunctional perovskite oxides are widely considered to be promising cathode materials for the commercialization of fuel cells, with cobalt-rich variants traditionally preferred. However, challenges such as instability at elevated temperatures and high cost hinder their commercial viability. To address these issues, this study successfully develops a high-performance, cobalt-free ternary cathode material, Ba_0.95Pr_0.05FeO_3-δ (BP5F), by substituting a small amount of Pr into the A-site of the perovskite parent BaFeO_3-δ (BF), tailored for bifunctional applications in both solid oxide fuel cells (SOFCs) and protonic ceramic fuel cells (PCFCs). The incorporation of Pr not only optimizes the crystal phase structure but also enhances the oxygen vacancy concentration and triple-conducting capabilities of BP5F. Consequently, this cathode material exhibits remarkable electrocatalytic activity at intermediate-to-low temperatures (ILT, 400–700 °C), with ultra-low area specific resistances of just 0.028 and 0.134 Ω cm² at 600 °C in symmetrical cells with oxygen ion- and proton-conducting electrolytes, respectively. Correspondingly, in single cells, the peak power densities reach up to 1.528 and 1.135 W cm⁻². Furthermore, BP5F demonstrates exceptional long-term durability, operating stably for over 100 h at 600 °C in both SOFC and PCFC single cells. These performance metrics position BP5F among the best-performing ternary perovskite oxides to date. Experimental results combined with theoretical calculations validate the critical role of Pr, establishing BP5F as a highly promising and economically viable bifunctional candidate perovskite cathode, thus providing a significant step towards the commercial development of fuel cell technologies.