Rational design of perovskite ferrites as high-performance proton-conducting fuel cell cathodes

The biggest obstacle to the commercialization of protonic ceramic fuel cells (PCFCs) is the lack of high-performance, low-cost cathode materials. Currently, the most promising cathode materials are cobalt-based perovskites; however, the unstable phases, poor thermomechanical compatibility with other PCFC components, high cost and unsatisfactory performance limit the viability of these materials. Here we combine ab initio simulations, molecular orbital insights, and A- and B-site co-substitution to develop a cobalt-free perovskite with outstanding performance. A- and B-site substitution in BaFeO3−δ, is found to promote the formation of oxygen vacancies (\({{{\mathrm{V}}}}_{{{\mathrm{O}}}}^{ \bullet \bullet }\)) and hydroxyl ions (\({{{\mathrm{OH}}}}_{{{\mathrm{O}}}}^ \bullet\)) while retaining structural stability. The best computationally identified material, Ba0.875Fe0.875Zr0.125O3−δ, showed exceptional oxygen reduction reaction electrochemical activity with a peak power density of 0.67 W cm−2 at 500 °C. This rational approach provides a strategy for designing high-activity, low-cost and cobalt-free perovskites, marking a significant step towards realizing commercially viable PCFCs.