A redesigned fuel-cell cathode reached 2.2 W/cm² and ran for 400 hours
An iron-based ceramic cathode improved oxygen and proton movement in tests of protonic ceramic fuel cells at 700 °C.
Editorial illustration — not from the study.
The study compared two related ceramic cathodes: a manganese-based material and an iron-based material. Both have a layered crystal structure used in fuel-cell electrodes, but the iron-based cathode had a more favorable arrangement of electronic energy levels between iron and oxygen atoms.
Calculations and experiments linked that arrangement to easier formation of oxygen vacancies, greater proton incorporation, and faster movement of oxygen and protons. The iron-based cathode also showed higher electronic conductivity and faster surface exchange and diffusion processes than the manganese-based material.
What the iron cathode does
Density functional theory calculations indicated that the iron-based cathode, La0.5Sr1.5FeO4+δ, has a more favorable alignment between iron 3d and oxygen 2p energy levels than the manganese-based La0.5Sr1.5MnO4+δ cathode. The calculations linked this alignment to lower energy requirements for forming oxygen vacancies, improved incorporation of protons, lower barriers for proton movement, and lower free-energy barriers for key steps in the oxygen reduction reaction.
Experiments found more oxygen-vacancy-related surface oxygen species, much higher electronic conductivity, and faster oxygen and proton exchange and diffusion in the iron-based material. Electrochemical measurements under different oxygen and water-vapor conditions indicated that it promoted several steps involved in the proton-related oxygen reduction reaction, including charge and proton transfer at the interface, oxygen reduction, and surface oxygen transport.
A fuel cell using the optimized iron-based cathode reached a peak power density of 2.2 W/cm² and a polarization resistance of 0.04 Ω cm² at 700 °C. The cell operated stably for more than 400 hours and outperformed the manganese-based cathode and many previously reported related cathodes.
Why the material matters
Cathodes in protonic ceramic fuel cells must support several linked processes: they must conduct electrons, take in oxygen, move oxygen and protons, and enable the reactions that produce electricity. The study suggests that tuning the electronic structure of the cathode material can improve these processes together rather than targeting only one of them.
The reported power density and more-than-400-hour operating test show that the iron-based material performed well under the study's conditions. The results also offer a materials-design approach for K2NiF4-type cathodes, a class of layered ceramic materials used in these fuel cells.
Evidence and caveats
The evidence combines density functional theory calculations with laboratory measurements of conductivity, oxygen and proton exchange and diffusion, surface oxygen species, and electrochemical performance. Tests using different oxygen and water-vapor conditions were used to examine the reaction steps promoted by the iron-based cathode.
The abstract does not provide the full cell design, the number of tested cells or repeat measurements, detailed degradation data, or the conditions and performance changes during the more-than-400-hour stability test. The findings therefore describe the performance demonstrated in this study rather than establishing how the cathode will perform across other fuel-cell designs or operating conditions.
// Source
Journal of Advanced Ceramics · 2026 · DOI: 10.26599/jac.2026.9221375
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