Cobalt doping as a microstructural optimization strategy for Sr2Fe1.5Mo0.5O6-δ cathodes in direct ammonia SOFCs for N2O abatement

• Abatement of nitrous oxide (N 2 O) flue gas using Direct Ammonia (NH 3 ) Solid Oxide Fuel Cell (SOFC); • Cobalt doping in Sr 2 Fe 1.5-x Mo 0.5 O 6− δ ( x = 0.05, Sr 2 Fe 1 . 45 Co 0 . 05 Mo 0 . 5 O 6− δ ) as a strategy to optimize microstructure and intrinsic properties for enhanced oxygen reduction reaction at intermediate temperature; • Cathode doping nearly doubles the maximum power density of the SOFC. Perovskite-type oxides are promising materials for mitigating nitrous oxide (N 2 O) emissions. Although widely studied for thermal N 2 O decomposition, their application in electrochemical N 2 O abatement in solid oxide fuel cells (SOFCs) remains largely unexplored. The double perovskite Sr 2 Fe 1.5 Mo 0.5 O 6- δ (SFMO) stands out for its mixed ionic–electronic conductivity and redox stability; however, it exhibits low power conversion efficiency when N 2 O is supplied to the cathode. This work focuses on improving SFMO performance by partially substituing Fe with small amount of Co (Sr 2 Fe 1.5- x Co x Mo 0 .5 O 6- δ , x = 0.05) to enhance its intrinsic and microstructural properties, aiming to improve cathode performance under N 2 O conditions in a direct ammonia SOFC (DA-SOFC), operating at 600–750 °C. Electrochemical impedance spectroscopy revealed similar reaction mechanisms in both compositions, despite notable microstructural differences caused by Co-doping. The denser SFCMO layers showed better grain connectivity, nearly doubling the peak power density (∼30 mW cm −2 ) compared to undoped SFMO, highlighting the beneficial role of microstructural alterations.