Effects of Sr-site deficiency on structure and electrochemical performance in Sr2MgMoO6 for solid-oxide fuel cell

Double-perovskite Sr-deficient Sr2−xMgMoO6−δ (x = 0-0.15) samples were prepared via a sol-gel route and evaluated as anode materials for solid-oxide fuel cells. The effects of Sr-site deficiency on lattice structure, electrical conductivity, thermal expansion coefficient (TEC) and electrochemical performance were systematically investigated. It is found that Sr-site deficiency within 0 < x < 0.10 increases the degree of B-site ordering but decreases the TEC value. The electrical conductivity increases with increasing x and reaches the maximum at x = 0.10. The Sr-site deficiency also increases the ratio of Mo6+, leading to enhanced oxygen vacancy concentration and reduced polarization resistance. With La0.8Sr0.2Ga0.83Mg0.17O3−δ as electrolyte and Ba0.5Sr0.5Co0.8Fe0.2O3−δ as cathode, the single cells with Sr2−xMgMoO6−δ (x = 0, 0.05, 0.10 and 0.15) anodes show the maximum power densities of 527, 551, 659 and 573 mW cm−2, respectively, in H2 at 800 °C. The x = 0.10 anode exhibits the highest power density due to its high conductivity, low overpotential and good catalytic activity. Single-cell tests indicate the potential application of the deficiency in Sr-site for Sr2−xMgMoO6−δ as SOFC anode material.