Enhanced Long‐Term Cathode Stability by Tuning Interfacial Nanocomposite for Intermediate Temperature Solid Oxide Fuel Cells

Abstract Performance durability is one of the essential requirements for solid oxide fuel cell materials operating in the intermediate temperature range (500–700 °C). The trade‐off between desirable catalytic activity and long‐term stability challenges the development and commercialization of electrode materials. Here an oxygen cathode material, Ba_0.5Sr_0.5(Co_0.7Fe_0.3)_0.69−xMg_xW_0.31O_3−δ (BSCFW‐xMg), that exhibits excellent electrocatalytic performance through the addition of an optimized amount of Mg to the self‐assembled nanocomposite Ba_0.5Sr_0.5(Co_0.7Fe_0.3)_0.69W_0.31O_3−δ (BSCFW) by simple solid‐state reaction is reported. Distinct from the bulk and surface approaches to introduce vacancies and defects in materials design, here the Mg²⁺ ions concentrate at the single perovskite/double perovskite interface of BSCFW with dislocations and Mg²⁺‐rich nanolayers, resulting in stressed and compositionally inhomogeneous interface regions. The interfacial chemistry within these nanocomposites provides an additional degree of freedom to enable performance optimization over single phase materials and promotes the durability of alkaline‐earth based fuel cell materials.