Strontium-free Ruddlesden–Popper cuprates (La1.7Ca0.3Cu0.75M0.25O4+, M = Fe, Co, Ni) as cathode materials for high-performance solid oxide fuel cells

Ruddlesden–Popper phases of the K2NiF4 type exhibit anisotropic lattice-oxygen mobility and hold promise as cathode materials for solid oxide fuel cells (SOFCs). However, most of these phases suffer from cation (e.g., Sr2 +) segregation, which hinders their commercialization. To overcome this limitation, we herein prepared Sr-free perovskite cuprates of La1.7Ca0.3Cu0.75M0.25O (M = Cu, Co, Ni, Fe) and investigated the influence of M on their lattice structure and their performance as SOFC cathode materials. The highest performance was achieved for M = Co, in which case an optimized Sc-stabilized-zirconia/Ni-YSZ-anode-supported cell without a buffer layer between the cathode and electrolyte delivered maximum power densities of 2.57 and 1 W cm−2 at 850 and 750 °C, respectively, and did not suffer from cation segregation. Thus, our work paves the way for the development of next-generation SOFCs and establishes important composition–structure–activity relationships for their cathode materials.