A real proton‐conductive, robust, and cobalt‐free cathode for proton‐conducting solid oxide fuel cells with exceptional performance

Abstract The development of proton, oxygen‐ion, and electron mixed conducting materials, known as triple‐conduction materials, as cathodes for proton‐conducting solid oxide fuel cells (H‐SOFCs) is highly desired because they can increase fuel cell performance by extending the reaction active area. Although oxygen‐ion and electron conductions can be measured directly, proton conduction in these oxides is usually estimated indirectly. Because of the instability of cathode materials in a reducing environment, direct measurement of proton conduction in cathode oxide is difficult. The La 0.8 Sr 0.2 Sc 0.5 Fe 0.5 O 3– δ (LSSF) cathode material is proposed for H‐SOFCs in this study, which can survive in an H 2 ‐containing atmosphere, allowing measurement of proton conduction in LSSF by hydrogen permeation technology. Furthermore, LSSF is discovered to be a unique proton and electron mixed‐conductive material with limited oxygen diffusion capability that is specifically designed for H‐SOFCs. The LSSF is an appealing cathode choice for H‐SOFCs due to its outstanding CO 2 tolerance and matched thermal expansion coefficient, producing a record‐high performance of 2032 mW cm −2 at 700°C and good long‐term stability under operational conditions. The current study reveals that a new type of proton–electron mixed conducting cathode can provide promising performance for H‐SOFCs, opening the way for developing high‐performance cathodes.