Topological Ion Optimized Composite Cathode for Proton‐Conducting Solid Oxide Fuel Cells

Abstract Proton ceramic fuel cells (PCFCs) are favored for their excellent performance under medium‐temperature conditions. However, their advancement is limited by sluggish oxygen kinetics and the lack of highly compatible cathodes. Nanocatalysts produced via in situ exsolution have emerged as a promising solution to overcome the limitations of conventional PCFC cathode catalysts. A novel three‐phase composite cathode, synthesized via in situ ion topology engineering, achieves enhanced performance in PCFCs. By introducing the transition metal V into BaCe _0.25 Fe _0.75 O _3‐δ (BCF), BaFe ₂ O ₄ nanoparticles are formed on the cathode surface through Fe‐Ba‐V ion exchange, simultaneously creating a BaCeO ₃ ‐BaFe _1‐x V _x O ₃ co‐catalyzed interface. This composite cathode exhibits superior oxygen adsorption‐dissociation capabilities and serves as an efficient proton conduction carrier. The self‐assembled BaFe ₂ O ₄ , with its low thermal expansion coefficient, reduces the material's overall thermal expansion and improves cathode‐electrolyte compatibility. Additionally, the cathode's stability and catalytic activity are significantly enhanced. PCFCs utilizing BCF‐V as the cathode achieved an impressive power density of 1.73 W cm ⁻² at 650 °C and maintained stable operation for over 200 h at 600 °C.