Enhanced activity and stability of Sr ₂ FeMo _0.65 Ni _0.35 O _6-δ anode for solid oxide fuel cells with Na doping

Sr _2-x Na _x FeMo _0.65 Ni _0.35 O _6-δ is synthesized as an anode material for solid oxide fuel cells. The effects of Na on the crystalline phase and electrical properties are investigated. The main perovskite phase changes into a Ruddlesden-Popper structure after reduction when x is less than 0.1, while the material with a higher amount of Na keeps the perovskite structure. FeNi _x alloy nanoparticles are exsolved during reduction, in which the content of Ni increases with the rise of Na amount. The surface oxygen vacancy concentration is also influenced by the doping of Na, and the highest value is reached when x is 0.1. Sr _1.9 Na _0.1 FeMo _0.65 Ni _0.35 O _6-δ anode exhibits the highest activity, and a single cell supported by a 300-μm-thick La _0.8 Sr _0.2 Ga _0.8 Mg _0.2 O _3-δ electrolyte layer shows maximum power densities of 1495 and 627 mW cm ⁻² at 850 °C with H ₂ and wet CH ₄ as fuels, respectively. The coking resistance of the anode is also improved with Na doping.