A comprehensive review on tuning Mn-Co and Mn-Cu spinel coatings via strategic doping for advanced solid oxide fuel cell interconnects

With the decreasing operating temperatures of solid oxide fuel cells (SOFCs), metallic components, such as interconnects and supports, have become critical to their structural integrity. Chromium-containing alloys are particularly promising for these applications due to their low cost, excellent electrical conductivity, and manufacturability. However, Cr evaporation and subsequent deposition onto the cathode—commonly referred to as Cr-poisoning—compromises cathode performance and reduces SOFC lifespan. To mitigate this issue, protective coatings, primarily transition metal oxides with perovskite or spinel structures, are applied to Cr-containing alloys. Among these, Mn-Co and Mn-Cu spinels stand out for their ability to suppress Cr diffusion, maintain low area-specific resistance (ASR), and achieve coefficients of thermal expansion (CTE) compatible with other SOFC components. This review examines the influence of doping elements, specifically transition metals and rare earth elements, on the performance of Mn-Co spinel coatings. Key aspects analyzed include improvements in ASR, CTE, and the coatings’ capacity to inhibit Cr diffusion, which collectively enhance the durability and reliability of SOFCs. Additionally, the mechanisms underlying these improvements are analyzed, alongside discussions on current challenges and future research directions for optimizing SOFC protective coatings.